Decarbonizing household heating: reviewing demographics, geography and low­carbon practices and preferences in five European countries

: What commonalities are there in sustainable or unsustainable heating practices in five high-income, high-emitting western European countries? What preferences do a nationally representative sample of the public in these countries hold towards low-carbon options? It is imperative that climate policy researchers and practitioners grapple with the difficulty of decarbonizing heat, which remains the largest single end-use service worldwide and which accounts about half of total final energy consumption. Based on a comparative assessment of five representative national surveys in Germany (N=2009), Italy (N=2039), Spain (N=2038), Sweden (N=2023), and the United Kingdom (N=2000), this study explores the demographics and geography of household heat decarbonisation in Europe. By analyzing our country level data as well as our combined sample of 10,109 respondents, it investigates how people conceive of the purposes of low-carbon heat, their preferences for particular forms of heat supply, and their (at times odd) practices of heat consumption and temperature settings. Grounded in its original data, the study organizes its findings inductively across the five themes of literacy (heating knowledge, awareness and control), sustainability (heating practices, dynamics and conflicts), temperature (heating satisfaction and preferences, desirability of change (low-carbon heating priorities, business models and trust), and culture (country and national variation). The study also explores intersections between these dimensions, using multivariate analysis, as well as how preferences differ according to varying types of actors as well as geography and space.

Decarbonizing household heating: Reviewing demographics, geography and low-carbon practices and preferences in five European countries

Introduction
It is imperative that energy and climate policymakers and researchers grapple with the difficulty of decarbonizing heating and cooling, because the largest single end-use service related to energy remains heating and cooling, accounting for roughly half of worldwide total final energy consumption [1] However, the International Energy Agency (IEA) also estimates that only 10% of heat production annually comes from low-carbon or renewable sources. In the European Union (EU), despite all of its progress towards setting ambitious energy and climate goals, 84% of heating and cooling needs are still met by fossil fuels [2]. Heat also remains one of the most significant contributions to European household carbon footprints, far more than from electricity or other household energy services [3].
Despite this almost obvious imperative of decarbonizing household heat, getting households to adopt low carbon forms of space heating and cooling is difficult. Krausmann et al. [4] caution that tackling energy consumption in buildings, especially heat, represents a "key challenge" for meeting and complying with global carbon targets. Hansen [5,6] argues that household heat consumption is so resistant to change because it is embodied in both existing long-lived infrastructures and social practices [5,6]. Other studies emphasize decarbonizing heat as a complex sociotechnical problem that involves a seamless web of infrastructure and building stock, patterns of incumbency and path dependence, the sales practices of installers and professional networks, and socioeconomic drivers such as income and poverty [7][8][9]. These contextual factors make heat perhaps more prone to "path dependence" [10] or "lock-in" [11] than other energy services or sources of supply. The implication from this growing body of evidence is that heating and cooling practices are unsustainable, and locked into staying that way.
In this study, we ask: What commonalities are there in sustainable or unsustainable heating practices in five high-income, high-emitting western European countries? What preferences do a nationally representative sample of the public in these countries hold towards low-carbon options? Aiming for an empirically novel and robust paper, we explore these aspects of heat based on an original large-scale survey in five European countries. Our final sample comprises 10,109 respondents spread across the United Kingdom (UK) (N=2000), Germany (N=2009), Italy (N=2039), Spain (N=2038), and Sweden (N=2023). Based on our survey data and results, we tackle many of these dimensions of heat head on, and explore: • Literacy, including heating knowledge, awareness and perceived or self-reported control (important themes in energy consumption research arising from [30][31]); • Sustainability, which includes heating practices, dynamics and conflicts (important themes in [32][33][34]); • Temperature, which includes heating satisfaction and preferences (important themes in [35][36][37]); • Desirability of change, which includes heating priorities, business models and trust (themes in [38][39][40][41][42][43][44]); • Country and cultural variation, and how our results differ across the five European countries (themes in [45][46][47][48][49][50][51]). Building on an analysis of these five dimensions, the paper then analyzes intersections among these attributes, actors, and some of the geographic and spatial implications of our research.
The paper proceeds as follows. Given that our contribution is intended to be more empirical than theoretical, and also that we had a copious amount of data to deal with (meaning the paper is "saturated" with findings or at least results), we did not have the space to present a literature review on heat or to posit some sort of conceptual framework on heat. Therefore, the Section 2 explains our selection of European countries before summarizing our research design (a survey instrument), data analysis techniques, and limitations. We then introduce our core Results organized thematically Figure 1 shows some of the demographic details of our final sample, which were ensured to be nationally representative for gender, age, income, and region. The survey sample had the added benefit of being very recent, with all respondents completing the questionnaire in 2020, making our results extremely up to date as of the time of publication. is the average household size of participants. C is self-reported level of education. D is gender. E is annual total household income. F is age. G is home ownership.

Data analysis techniques
The survey results were first analyzed descriptively and at times with the help of frequency analyses and single level statistical analyses. However, in order to evaluate possible significant G associations among the variables in our study, we started with a correlation analysis. We calculated Person's correlation coefficients and assessed their significant at the 0.05 and 0.01 level, with a twotailed test. We also used a Mann-Whitney U test to examine any significant differences at 0.05 level between one country's responses with all of the other countries. For this, all 4-and 5-point Likerttype answers were recoded into the same order (e.g. lowest number disagree and highest number agree). We also used Benjamini -Hochberg Procedure as a post-hoc test to control for false positives [52]. A second part of our analysis, mentioned mostly in the Discussion section, consisted in testing if significant differencesin literacy, willingness to change and energy-related behaviorscould be observed depending on the country of respondents, or on their house ownership. To this aim, we carried out an analysis of variance (ANOVA) to see if, overall, group means were significantly different. We completed this analysis with post-hoc tests, to compare groups in pairs and identify which particular differences were significant. One assumption of classical One-Way ANOVA is homogeneity of variance, which means that the variance among the groups should be approximately equal. However, this assumption was violated in our sample, as confirmed by the Levene's tests for homogeneity of variance that we carried out. Accordingly, in order to perform a robust analysis, we replaced classic ANOVA with the Welch test for the equality of group means, which does not require variance homogeneity. Similarly, we performed a Games-Howell post hoc analysis [12] to carry out robust pairwise multiple comparisons. Although similar to Tukey's test, the Games-Howell test does not assume equal variances and sample sizes.
Lastly, we looked at the interclass correlation coefficients (ICC) that we calculated after building empty multilevel regression models [13,14] which just included the constant term with fixed effects depending on the country of respondents. We did this analysis in order to see which proportion of the variance of each dependent variable was attributable to the country of respondents (and which was the residual part).

Limitations
Proceeding on this path, our aim is for an empirically robust and novel paper, one that the methods literature describes as "new applications of existing methods … (e.g. to different regions, contexts or research questions), as well as through analysis of new types of evidence or data" [15 pg,14]. This means most of our analysis below is grounded not in theories or broader sets of literature but the data itself, similar to the "grounded theory" approached used in some disciplines such as ethnography, geography, and sociology. There also wasn't sufficient space to test theoretical propositions in the survey alongside all of our practical questions. Even though this type of paper has novelty for its large empirical dataset, we nonetheless hope that it can be used to help inform others seeking to develop theory or also calibrate energy models, predict energy-related consumer behaviors, and other research designs. Moreover, rather than split this paper into a number of derivative papers that "slice" its results into separate outputs, our intent was to place everything in a grand, single "big" paper. This makes it long but also (we hope) more coherent and complete.
Although we believe that the paper has a high degree of validity and rigor, our research design does have some notable limitations. First, while our five national country samples are representative in terms of gender, age, income, and location, we cannot guarantee representativeness beyond these categories, e.g. household size, education or home ownership. Second, because our data are representative, these include many respondents who may have little awareness or knowledge about heat, and many who may not have actually adopted low-carbon heating technologies. Third, we treat responses as stable and fixed, soliciting them at a single point in time, whereas in reality they are flexible, fluid, and co-constructed over time. Fourth, due to space constraints, we could not deeply analyze all 23 survey questions in this paper or present all results in their entirety.

Literacy: Heating knowledge, awareness and control
This section is our first to present our results; it does so by focusing on the heating knowledge or energy literacy aspects of the survey, including their attention to and awareness of heat in the household. This also included how heat is perceived to be provided, and how households reported they managed heat in the home.

Knowledge and attention/awareness
As a starting point, respondents were asked "How much would you say you know about how your home and water is heated?" As Figure 2 reveals, self-rated heating knowledge was generally high, with most respondents indicating they had moderate to advanced heating literacy. Self-described advanced literacy in particular varied by country, with the UK and Italy reporting far higher rates than Sweden or Germany. The level of attention households reported paying to heat also varied considerably, with more than one-quarter of all respondents suggesting they had "none at all" to "not very much." Conversely, those reporting a fair amount to high attention to heat were the largest in Italy (93.5%), followed by the UK (84.7%) and Spain (78.6%). Sweden had by far the lowest prevalence of attention (43.2%) perhaps related to their high incidence of district heating (42.8% of homes in Sweden report being supplied by heat networks or district heating systems). We also see the Swedes having some of the lowest numbers of stated control over their heating systems as a result, which also implies that low-carbon systems do not always go hand-in-hand with perceptions of enhanced personal control. 17 Figure 2: Heating knowledge, literacy, and awareness of heat self-reported by respondents (N=10,109). Panel A is self-reported advanced literacy by country. B is self-reported knowledge of heating. C is reported level of attention to heat. D is the percentage of respondents with a high attention to heat. "High attention to heat" refers to respondents who either answered either "a fair amount" or "a lot."

Current heating
When asked "What is the main way you currently provide heat in your home?" most respondents (almost half) relied exclusively on gas, despite offering the survey in five very different countries, policy environments, and energy markets (see Figure 3). When looked at by country, and the % heated by fossil fuels (gas, oil), variation was significant with the UK (79.3%) and Italy (69.8%) having a dominance of fossil fuel heating contrasted with Sweden at only 3%. We also asked how homes currently pay for their heat. About half (52.4%) pay the conventional way of purchasing a volume of electricity or gas and paying monthly to quarterly bills. A solid 29.6% of respondents paid for heat via a network or a building manager to guarantee a set temperature. About 18% do not know or selected another type of payment service. As a particularly promising sign for possible decarbonisation potentials, more than 60% of respondents in the UK, Spain and Italy all reported paying for their heat via an individual oil or gas boiler, heat pump, or electricity.  (n=10,109). Panel A refers to the type of heating system reported by respondents. Panel B the percentage of participants who said they had fossil-fueled heating. C describes how households currently pay for their heat. D refers to those households that pay individually for heat from an electricity network, heat pump, fuel oil, or gas boiler. DJ=district heat. "Fossil-fueled heating" refers to gas, fuel oil, and liquefied petroleum gas.

Control, management and use
Our final aspect of literacy and knowledge explored related to heating control and use. Across the survey population, many homes have limited to no heating controls at all, and only 11.4% reported having advanced or smart heating controls in Figure 4. The prevalence of no to limited heating control was reported to be highest in Spain (58.4%) and Sweden (56.6%) followed by Italy (50.2%). When asked who uses or controls household heating, most respondents (70.9%) suggested that they themselves did, followed by their partners (34.1%). This personal control was reportedly the highest in the UK (83.1%) followed by Spain (77.4%) and Germany (73.9%). As R877 (UK) echoed this concern when they said: Once my fiancé called our boiler man saying there was some trouble with the heat. Turns out she hadn't turned it on!! R812 (UK) wrote about how confusing it was to learn to use their new heating system, saying: We bought new property with heating arrangements already made. They provided a complicated handbook on how to install the system but no advice on how to use it! R2334 (Germany) seems to have learned an even harsher lesson about control, noting: When refilling the heating with water, I turned on the wrong tap and I got an involuntary shower!! These statements all imply that as important as heating control is, it remains unintuitive for many households and also may serve as evidence that more automated or smart controls can minimize many of these instances of poor or confused control. They also buttress the finding that simplicity and comprehensibility should be an inevitable characteristic of the future smart control systems.

Sustainability: Heating practices, dynamics and conflicts
In this section, we look more closely at our results over heating practices. This includes how important homes view heat as an energy security or services issue, as well as heating practices, habits and profiles, and how much these connect with the goals of decarbonisation and sustainability (or not), such as opening windows or the numbers of heated rooms. Lastly, this section examines issues of conflict that may emerge over such heating practices and dynamics.

Importance of heat as an energy service
To begin, Figure 5 illustrates how our respondents, as a whole, strongly believed heating was the single most important energy service (compared to say lighting, entertainment, refrigeration, etc.). This belief in heat as a critical energy service was the strongest in Germany (61.1%) and Sweden (59.5%). However, it is perhaps striking to non-Northern Europeans that heat is valued as the most important service in almost half of respondents in the milder Mediterranean countries of Italy and Spain.

Wasteful and unsustainable practices
Our next questions were intended to interpret the extent of possibly wasteful or inefficient heating practices. We asked respondents if it was acceptable to keep the heat on all year round, with more than 17% in Figure 6 indicating they agreed or strongly agreed. More than 70% of people in the UK, Italy, and Germany also reported opening windows in the middle of winter to let in fresh air. Respondents also reported a perceived necessity of heating for a variety of other aspects including heating every room (even if rooms are not in use, 41%), heating for pets (27%), and opening windows in the middle of winter (68%). Similarly, 38% of all respondents agreed or strongly agreed that homes needed to be warm enough to wear shorts or t-shirts in the dead of winter. This belief was the strongest in our two northernmost countries of Sweden (45.3%) and the UK (38.6%), which is slightly surprising, given these countries have the coldest climates (and thus one may expect greater heat awareness or more reasonable expectations).

D
In our previous apartment, we had boiler that we called "Baby," for it needed to be guarded and fed ;) Whenever anyone asked if we had children, we would laugh and say "we always have Baby, baby." These examples, while rare and hardly representative, surely reveal the complex and non-rational ways that people engage with their heating sources.

Heating activity or preference conflicts
These sets of questions focused on heating practices and dynamics, especially possible "thermal conflicts" in use and control in the home [16] . Respondents confirmed in Figure 7 that heating was likely to lead to possible tension or conflict with housemates, couples and partners, landlords and tenants, and children and parents (all roughly one-third). About one-fifth of respondents suggested it was likely to highly likely conflicts between hosts and guests, or neighbors, could also result. Potential conflicts with landlords were reported to be most pronounced in the UK (42.5%), followed by Spain (40.9%) and Sweden (40.5%). Germany, by contrast, seemed to have the best or kindest perceived landlords and property agents within the bunch (only 30.2% of Germans spoke about possible heating conflicts with them), or perhaps the inclusion of heating fees into rental contracts and leases which would minimize possible contact with landlords or heat suppliers.  If you run the hot tap in one room and someone is in the shower, the shower runs cold and you hear them scream These comments all reflect a range of more personal interactions with heating systems or the people that use them, ranging from the deviant and illegal to the humorous, endearing and playful.

Temperature: Heating preferences and satisfaction
This section explores our results concerning temperature preferences, how warm households reporting desiring their indoor climates for the summer and winter. It also examined how satisfied they were with their heating systems. Figure 8 depicts preferences for preferred (heating) temperature in the winter, with many respondents expressing 20 degrees (26%), 22 degrees (17%), and 21 degrees (17%), but the rest (40%) preferring a great range of other temperatures, some as high as 30, others as low as 2. This could reflect a range of preferences or even a lack of knowledge about temperature. Either way, our respondents reported a great variation in preferred household temperature in the winter, with no single temperature occupying more than 26% of self-reported preferences. Preferences for very warm homes (greater than 25 Degrees) were the strongest in Spain (15%) and the UK (13.9%). Sweden stands out as perhaps the most reasonable country, with only 6.7% of respondents arguing homes would be excessively warm, followed by only 7.1% of German respondents.

Figure 8: Preferred temperatures in Celsius identified by respondents (n=10,109). Panel A refers to preferred winter temperatures and Panel B preferred summer temperatures.
A preference for at times extremely warm homes came out of our qualitative material as well. R1139 (UK) expressed satisfaction with warm temperatures by noting: When we had friends over they made a joke that our home is always warm because we're trying to replicate life in the Caribbean R7032 (Spain) added that: My children always complain that my house is too hot in winter, but I am in a T-shirt and shorts. R9493 (Sweden) similarly said that: We are used to high temperatures in winter indoors so you can have comfortable clothes type t-shirt and shorts. I always freeze indoors and everywhere here in Sweden. R9070 (Sweden) even said they have no need for a temperature dial, control, or thermometer, noting: I don't need a thermometer -I just see how much clothes I need to put on. Some family norms went the other way, however, towards extremely cold or almost negligent levels of heat for their children. As R9262 (Sweden) admitted: I

had an oil pan in my childhood home. Dad was stingy and wanted to save on oil and firewood so I had 14 degrees in my room one winter. This was also due to poorly insulated windows, my hair would blow indoors whenever it was windy.
Similarly divergent preferences were stated for preferred coolness in the summer, with no single temperature capturing more than 23% of respondents stated preferences. Preferred summer temperatures were even more distributed, with only 20% preferring 20 degrees followed by 18 degrees (15%) and 22 degrees (8%). The remaining 57% all preferred at times drastically different summer temperatures.

Satisfaction and dissatisfaction
In terms of satisfaction, most respondents (more than half) were satisfied with their current heating and hot water system and 27.3% were very satisfied (see Figure 9). The UK had the highest proportion of those satisfied to very satisfied (82.9%) followed by Spain (82.5%), Italy (80.5%) and Germany (80.5%). This high rate of in the UK-dominated by gas boilers of perceived high efficiency-may make it a difficult market for alternate heating systems of any time to penetrate. Conversely, even though they had the lowest-carbon heating system across the five countries, the Swedes were the most dissatisfied across all countries. 27 Figure 9: Levels of satisfaction with current heating system (n=10,109). Panel A shows stated satisfaction with current heating systems across the entire sample, Panel B organized by country.
That said, a host of qualitative comments underscore just how bad people's heating systems are in practice: R28 (UK): My current heating system is a communal "hot air vent" system, grossly out of date, inefficient and just provides clouds of dust whenever it's switched on. R70 (UK): My heating is a nightmare R1172 (UK): My heating system is rubbish and always feel cold it's hilarious R1608 (UK): Heating system never worked so started fires R5817 (Italy): Once we had a boiler so bad we had to take a shower by boiling the water on the fire Two respondents mentioned serious accidents related to their heat: R1910 (UK): Boiler exploded almost killed my friend when she was taking shower. Some people died in bath next door. R4107 (Italy): Sometimes the boiler in our house would just stop working. We came home one day to find it had burnt our house to the ground. R2874 (Germany) spoke about a heating system so bad in the winter, they had to sit in the car (outside) to be warm: One winter our heating failed, the apartments were cold, no technician could be reached, it was just the on and off button, we took turns in the house sitting outside in our Mercedes [automobile] to stay warm, otherwise everyone sat in thick clothes and waited their turn. R4906 (Italy) had a clever strategy for dealing with "bad" or malfunctioning boilers, they stockpiled extra ones for redundancy: I once had three boilers and one replaced the other in an emergency, now unfortunately it is no longer possible R10043 (Sweden) developed an intimate ritual of care needed to maintain heating Unusually, you have to ventilate the elements once a week all the time otherwise the heat will disappear from them and the hot water takes an eternity before it arrives, you can flush the tap fully for up to 5 minutes. It gets old having to continually do this. These statements firstly indicate just how "bad" people's heating is; in some cases not even functional yet alone optimal or low-carbon. Moreover, it reveals some of the ingenious coping strategies people utilize to deal with coldness, such as wearing thick clothing, sitting in heated cars, burning fires, or stockpiling spare parts.

Desirability of change: heating priorities, business models and trust
In this section, we explore the likelihood that respondents suggested they were to adopt lowcarbon technologies or change their practices. This includes the desirable (and undesirable) attributes of low-carbon heat, as well as policies and business models (such as heat plans, heat as a service, and retrofits) alongside issues of trust.

Likelihood of changing or adopting new technology
We asked how likely respondents would be, if they were given the opportunity in the next few years, to change their heating to any number of fuels. In Figure 10, you can see that most suggested they would prefer to switch to solar (32%) or gas (28%). Interestingly, hydrogen was one of the least favored options, being almost equal (11%) only to oil in its popularity across the countries. Solar heating in particular was most preferred in the UK (43.2%) and Germany (36.1%). We also asked respondents in open-ended financial terms how much extra they would be willing to pay, per month in Euro, for low-carbon heat. Although one third (33.4%) said "nothing," one-fifth (19.7%) suggested more than €50, indicating the two poles of the spectrum. Almost half (46.9%) of Swedish respondents, and roughly one-third of Italian (37%), Spanish (35%), and German (31%) also indicated they would pay more than €20/month for low-carbon heat. At the extreme end of the spectrum, one German respondent stated they would pay €20,000/month for low-carbon heat and one Spanish and Swedish respondent each said they would pay €99,999 for low-carbon heat, the maximum number allowed by our survey, perhaps indicating a desire to capture the "infinite value" of mitigating climate change.  (n=10,109). Panel A shows the likelihood of changing heat to different sources for the entire sample. Panel B shows respondents likely to very likely to adopt solar heating by country. Panel C how much extra respondents stated they would pay per month for low-carbon heat. Panel D shows by country how many would pay more than €20/month.

Valuable attributes of low-carbon heat
We asked respondents about the attributes they most valued about potential low-carbon heating systems with the results shown in Figure 11, ranging from convenience (make life easier, 53.6%) to save time (36.4%) to protect the environment (69.7%). In terms of the operational features or performance criteria of a heating system, respondents highly rated all of the attributes we tested, including having an easy user manual and interoperability with other devices to strong manufacturer guarantees and reliability and ease of use (see Figure 11). Source: Authors As Figure 11 indicates, reliability and ease of use were the highest preferred attributes, one that also was consistent across all five countries examined and consistent in our qualitative material. Indeed, there more than 100 respondents (!) mentioned heating systems breaking down on Christmas or during holidays, as R6751 (Spain) put it: Our heating normally works well, but when we have had a fault in the boiler, it has been festive and cold dates, such as December 24, when there is no technician to repair it, and then for 2-3 days we are without heating and that is when we realize quickly the value of having heating at home. R7474 (Spain) talked about reliability issues that crop up due to their boiler literally because of birds: I have an individual diesel boiler to heat the house and it is necessary to clean the gas extraction duct every very short time since there are birds that sneak inside and then they cannot get out. R10094 (Sweden) remarked how even their district heating system can have reliability problems: The heat pipes broke and we were without heat for 1 month, went with winter clothes indoors in September month.

Business models
We explicitly tested perceptions and preferences for 8 emerging business models in the survey as well, framing them and offering slight definitions as follows: • Heat output as a service (e.g., paying a monthly fee to lease and maintain a heating device, with the provider offering fuel and heat) • Heat outcome as a service (e.g., like heat output as a service, but customers are charged for warmth rather than heat) • Warmth payment plan (e.g., charging a house for a set number of warm hours per month)

C
• Energy payment plans (e.g., bundling a warmth payment plan with other energy services such as electricity or lighting) • Asset leasing (e.g., service provider charges a fixed monthly fee to lease the heating appliance, including maintenance and repairs; at the end of the contract, customers can buy out the appliance or have it removed) • Efficient asset leasing (e.g., same as asset leasing, except with some kind of performance guarantee) • Low-carbon heating retrofits • Community contracts between neighbors (e.g. peer-to-peer energy trading) None of these were strongly supported or supported by more than about a quarter of respondents (see Figure 12), although retrofits (26%), bundled energy plans (24%), and heat as a service (23%) were the top three preferred business models within this family of business models. Surprisingly, support for P2P trading was not more prominent; even in the country with the highest percentage of preferences, this peaked at only 22.9% of our survey sample. Indeed, at least in Italy, P2P contracts became theoretically feasible on February 2020 without a technical regulation clarifying their practical aspects. At the time of the survey, most participants still did not likely know about their existence, and this was probably reflected in their answers.  (n=10,109). Panel A shows responses across the entire sample, people answering "I would support business models related to …" Panel B shows responses to "I am interested in P2P heat trading" organized by country.

Trust
Most values, beliefs, and even perceptions and preferences do not exist by themselves, but are shaped by the statements of others (what others know), making communication and trustworthiness essential factors in how people make decisions and consume information [17][18][19]. In terms of who might implement these business models, steer and shape them, or otherwise disseminate information (or even knowledge) about them, across the entire sample the most trustworthy entities were deemed to be technology suppliers (54%) and professionals such as architects, engineers, and technicians (53%), but not social media (22%), traditional media (29%),

B
or even friends (39%) (see Figure 13). This has some potentially profound implications for communication and marketing activities, especially as it implies that self-rated trust is lower among friends, neighbors, and family than government. (This finding also buttresses the one above about relative disinterest in peer-to-peer trading, as homes likely would not want to trade energy with those they do not trust). It lastly speaks to the powerful credibility that our respondents seem to enshrine in tradespersons and professionals. Within the countries, the Italians and English were most likely to trust only themselves; the Italians and Spanish had more trust in scientists and researchers; and the German and English had the least trust in government.  (n=10,109). Panel A shows responses across the entire sample to "I find the following actors trustworthy," Panel B answers to "I trust …" organized by country.
It is particularly striking that energy suppliers were the fourth most trusted entities out of the 13 categories (at slightly less than 51%) we mentioned in the survey, coming only after technology suppliers (54%), professionals (53%) and Scientists (51%). This is because in our qualitative data, about a third of the open-ended comments (from more than 1,300 respondents) actually were complaints about either heat and energy providers or installers and engineers. R37 (UK) wrote: The electricity has gone rogue.

Culture: Country and national variation
Interestingly, and shown in Figure 14, there were fairly large differences in responses country by country that arose from our findings as well. This includes the finding that Germans are far more likely to heat all year round. Italians are far more likely to heat every room. Saving money from heating systems was far more preferred in Spain. Swedes are far more likely to desire heat for their pets. British respondents prefer very cool temperatures. 34

Germany
In Table 1, we report statistically significant differences in responses between Germany and the other four countries. When disaggregated by country, Germany was surprisingly the "worst" with 34.7% of respondents indicating this was acceptable heating behavior to heat all year round compared to 22% or less across all other countries. This, again, reveals a possible paradox as Germany is often promoted as an exemplar of renewable energy diffusion, energy sustainability, and environmental awareness about energy [20,21]. German respondents were also fans of opening the windows in the winter compared to the other countries, and they also more strongly viewed heating as the most important energy service in a household.

Table 1: German purposes, preferences, and practices of heat compared to all other countries
As a possible explanation for some of these results, in more than 90% of homes in Germany, both heating and domestic hot water are typically supplied by one and the same heating appliance. Shutting down the heating appliance is, therefore, not possible during summer as hot water is needed all year round. Other Germans may have vacation houses and prefer to keep those heated to avoid damaging the building. Moreover, many Germans prefer to open or tilt the windows in winter to get fresh air and are quite resistant to restrict ventilation rules like carrying out shock ventilation for short periods in the morning and evening instead of tiling the windows. Even in passive energy houses with ventilation systems and heat recovery, the literature suggests that Germans feel they do not have enough fresh air and must open windows to compensate [22].

Italy
Italy deviates from our full sample and other countries in interesting ways as well. Italian respondents consider themselves very knowledgeable about heat and hot water, consistently with other studies about indoor thermal control [23]. They report more direct control over their heating systems. They believe heating is important for health and also that freshness is desirable in the winter by opening windows. Indeed, more than half (52.7%) of Italians believe they need to heat every room. They lastly favored retrofits far more than other country groups, perhaps since building retrofit is considered a common action, and construction output has decreased in the past few years [24]

Table 2: Italian purposes, preferences, and practices of heat compared to all other countries
As an explanation, in Italy most homes still have one boiler for both direct hot water and space heating, but may operate the system to be completely separated (through thermostats or simple on-off on the space heating system). Hot water may have a dedicated system with a storage for each bathroom in very old houses, and this is typically electrically driven. Only in new construction, which captures less than 10% of the housing market over the past decade [24], have thermostats been positioned in all thermal zones of a house, enabling possible enhanced heating control. Lastly, it is interesting to note that, despite the general slow trends of the Italian construction sector, Italians seem more willing to change their heating system, especially to a new gas boiler or a solar heating system.

Spain
Given Spain's more moderate climate, respondents suggested lower means for preferred winter and summer temperatures, and Spanish respondents were less likely to heat all the time in the winter and to heat for pets. Spanish respondents also rated lower the aspects of heating for health or heating for the strength of a building. In terms of country preference, saving energy was far more preferred in Spain (71.4%) and the UK (71.4%) than in Sweden; saving money was far more preferred (67%) in Spain as well than in all other countries. Protecting the environment was most strongly preferred in the UK (74.8%). Also, the mean rank of conflicts among housemates overheat was much higher in Spain than in the other countries. Spain lastly had the highest reported scores about household willingness to try out new heating systems.

Questions
Country groups

Table 3: Spanish purposes, preferences, and practices of heat compared to all other countries
As an explanation, Spanish households may think that it is cheaper to switch off the heating system when going to bed or when leaving the house to go to work and switching it on when arriving home in the evening that to keep the heating on all day. Most Spanish households have a gas boiler for heating and domestic hot water and a thermostat in the living room for temperature control; the gas boiler allows changing from winter mode (heating and domestic hot water) to summer mode (only domestic hot water), usually the change is done in April-May and in November by the user. The fact that usually only one thermostat is available in most households could explain the higher rate of conflicts in the household due to thermal comfort, especially if one part of the house/apartment is facing south and the other north, which could mean very different indoor temperatures due to passive sun heating even in the winter season. The higher thermal discomfort and higher household conflicts could explain the higher willingness of Spaniards for a change in the heating system, but probably also the perception that heating is expensive and finding cheaper options is a need. Moreover, just recently Spanish people have started to wear t-shirts in winter, so lower heating temperatures used to up to now are allowed if light sweaters are used; but these low temperatures could also be due to the perception of the high cost of heating and the strong media campaign undertaken in the last years showing that decreasing 1 ºC the indoor temperatures means 8% less gas use and, therefore, cheaper heating bills.

Sweden
More than one-third (38.3%) of Swedish respondents stated they needed to heat for pets even though Veterinarians have indicated such heating is not necessary. This perception that pets need warm homes not only shows lack of possible heat literacy. It could also be that people in colder climates such as Sweden think more about the need for heating pets and they expect and experience harsher winters. In addition, we see the Swedes having some of the lowest numbers of stated control over their heating systems as a result, which might be interpreted as the different perception of control embedded in the culture. Swedes report far less knowledge about heat than the other countries, much lower attention to heat, and higher scores for believing in the necessity of heating for the strength of the building. Apart from landlords and tenants, Sweden has significantly much lower average scores for other forms of heating conflict, which might be attributed to its consensus-oriented culture. They were lastly less concerned about issues such as privacy and trust.  . 1=Nothing at all to 4=A lot). b Reported as mean values of 5-point Likert type questions (e.g. 1=Strongly disagree to 5=Strongly agree; 1=Very unlikely to 5=Very likely; "Don't knows" have been reported as missing values). c Count is frequency to those selecting the answer. d Temperature reported as mean degrees in Celsius.
* Mann Whitney U test **Chi-Square Color highlight indicates significant at p<.05.

Table 4: Swedish purposes, preferences, and practices of heat compared to all other countries
As a further explanation, in Sweden, most of the buildings are heated either by district heating or electrically driven heating (and cooling) system such as heat pumps. For district heating, when the average temperature over the day is higher than 16 ºC, the pump for the district heating is turned off and when the average daily temperature goes lower than 16 ºC, the pump will be turned on automatically. This means the residents do not have to turn on or off anything in their heating system. Similarly, for the buildings which are heated by heat pumps, they do not need to turn off their heat pump during summer as it is also used for direct hot water production. So, the residents do not turn off the heating system any time of the year. Therefore, we guess that there might be some misunderstanding on what "keep heating on" would mean. Occupants residing in rented apartments where heating is a hidden part of a monthly fee would have even less of an incentive for proficient or sustainable heating use. Sweden is also a heating regime dominated by little public resistance or involvement, and strong support for incumbent firms and a natural monopoly on district heating [25]. Table 5 offers a high-level summary of statistically meaningful differences in responses between UK residents and the other countries. UK respondents reported being more knowledgeable about heat and desiring more control. They also had higher degrees of satisfaction, and to heat every room. Data and privacy issue were rated as more significant in the UK as well. UK respondents tend to trust friends, family and neighbors more, compared to the others. UK respondents also reported trusting themselves more, perhaps fitting in with a mentality of "being the king of their castle". The heating market is more dominated by gas in the UK as well, because of (in part) a government action in the 1990s to enhance the energy efficiency in the building sector in addition to campaigns in the 1960s and 1970s to convert homes from town gas to natural gas [16].  Interestingly, very cool temperatures (less than 17 degrees) were strongly preferred in the UK (50.2%) compared to all of the other countries in the sample. This could be a slow cultural adjustment to colder homes in UK, due in part to older classes of houses (many built in Victorian times) designed to be heated one room at a time via a fireplace and having poor energy efficiency. This may also reflect class issues embedded in social norms, as for instance the very wealthy upper classes and their houses, as well as the boarding schools they attended, were historically known to be very cold with no central heating [26]. While today central heating is common in the UK, many still live in Victorian era houses which are hard to heat. It is the wealthier middle-classes who are more likely for example to retrofit their homes to become more energy efficient [27], whilst many on lower incomes suffer from fuel poverty as a consequent of living in poor energy efficient homes. Many more homes in the UK are in fuel poverty and unable to afford warmth than in other countries in our sample, with fuel poverty described as a "national crisis" [28]. It could also be that given more UK homes have boilers they can control, they may manually keep temperatures lower to save gas and thus money (or carbon). The preference for lower temperatures might also be explained by the high relative humidity in general in the UK. In order to feel comfortable with such high humidity, they may believe that temperature must be reduced.

Discussion: Interconnections, actors and geography
Our survey results not only offer insights by theme or category of the survey, or country location, they also offer insights when analyzed using more robust statistical procedures. Here we focus on three we found most interesting: interconnections, actors, and geographic space.

Interconnections
When examined through more sophisticated multivariate analysis (to complement our univariate and bivariate analysis above), we do see some compelling interconnections and intersections among the different aspects of our survey as well as demographic attributes.
In Table 6, we observe a positive significant correlation of the household income with the habit of keeping the heating system operating the whole day. However, as expected, a higher income also correlates with the willingness to pay more to switch to low carbon energy sources, associated to a better awareness and engagement towards energy saving and pro-environment behaviors. -.044 ** .247 ** .092 ** -0.001 .026 ** .188 ** -.037 ** -0.003 .066 ** 0.000 .059 ** .044 ** 1 * p < .05; ** p < .01. Table 6: Pearson coefficients for heating practices, preferences, and demographic attributes across five European countries (N=10,109) Source: authors Surprisingly, we see that energy literacy is not correlated with the intention to change the energy source to solar. This may pave the way toward a much needed awareness campaign, focused on solar energy, developed for a general audience, of different cultural and education backgrounds.
It seems that younger people, and those with more children at home, are those more willing to change. Therefore, a possible positive trend could be observed in the short future. Results also show that literacy increases with age and is higher for males than for women. The low-attention attitude of wearing T-shirts and shorts at home all year around is, unfortunately as expected, associated to the practice of keeping the heating on the whole day. This practice is for example common in Sweden, as shown by 45.3% of respondents.

Actors and households
We also examined our results through the lens of actors, or at least how different types of households-those owned, rented, in social housing, and so on-may have meaningful differences across the survey evidence. As group variances were not homogeneous, we used the Welch test in lieu of the classical One-way ANOVA and carried out the Games-Howell post hoc analysis [12]. Welch tests are significant for all the selected variables, with p values always less than 0.001. These findings highlight the role played by the country of respondents in affecting energy-related behaviors, probably due to a variety of local differences (social, cultural, economic and regulatory aspects; climate conditions, etc.). In Table 7, we group survey observations by property ownership to see if literacy, willingness to change and behaviors were significantly different while comparing house owners, tenants, people living in social houses and those paying a mortgage. In this way, we carried out a variance analysis considering an economic variable, to evaluate its impact on energy-related behaviors and attitudes.   Table 7 indicates, almost all Welch tests are significant, excluding that of temperature in winter, which looks like a very "individual" attitude. Respondents who pay a mortgage and houseowners are better willing to pay extra fees for a low-carbon energy system, since they probably have a long-term vision, are concerned and care about the environment. As expected, they showed a better literacy with respect to the topic. This may be motivated by their general higher willingness to invest and ask for credit, or by their better economic condition, since they may have access to credit through their mortgage, for instance.

Games-Howell Post-hoc Analysis
By contrast, respondents living in social housingand, most probably, not charged for energy fees or maintenance costsact less responsibly, for example by keeping the heating on the whole day or by wearing light clothes even in winter. This is also partially true for tenants because they are typically less aware of the specificity of energy bills and paying fix maintenance costs does not provide a clear understanding about energy consumption. In addition, people living in social houses seem to pay less attention to summer cooling setpoints, while no significant differences are observed about heating temperatures in winter.
Willingness to switch to solar energy as thermal vector are in general high, with a relatively minor difference among the categories, except for the respondents paying a mortgage and those of the other categories.

Geography and space
Lastly, intersectional preferences and findings emerge via a geographic and spatial lens as well. For instance, the belief about wearing summer clothing in the winter was the strongest in our two northernmost countries of Sweden (45.3%) and the UK (38.6%), even though these countries have the coldest climates (and thus one may expect greater heat awareness or more reasonable expectations). The cold season may merely be too long in the minds of respondents to wait for summer to wear shorts and T-shirts. Furthermore, almost half (46.9%) of Swedish respondents, and roughly one-third of Italian (37%), Spanish (35%), and German (31%) also indicated they would pay more than €20/month for low-carbon heat. The UK and Sweden may need constant heat in the winter months, unless occupants live in a passive house, and different than the milder winters in Germany, Italy and Spain. Table 8 shows the analysis of variance we carried out to see if significant differences in mean literacy, willingness to change and energy-related behaviors could be imputable to the country of respondents. As expected through the survey observation, a large difference is found out for the temperature setup, with a more significant ANOVA for the summer temperature than for the winter one.

Table 8: Examining geographical and spatial differences in low-carbon heating responses across five European countries with Welch tests
To investigate this further, in Table 9, we reported the interaclass correlation coefficients calculated for empty multilevel regression models with fixed effects [13,14], with observations grouped by country. These indicate the proportion of variance explained by the grouping structure, for each variable. As the table shows, the habit of keeping the heating on all day has 20% of variance at the country level, whereas all the other variables exhibit a smaller proportion of variance that depends on the country.

Conclusion
The influence of demographics and geography on decarbonizing household heat-rooted in stated knowledge and literacy of heating, heating practices and dynamics, temperature preferences, priorities and willingness to change, and country variation-is important and complex. In terms of knowledge and literacy, a majority of our respondents across the five countries report relying exclusively on fossil fuels (especially gas) for their heat, and many homes reported using this gas inefficiently, that is almost 90% stated they have limited to no heating controls at all. Qualitative statements from respondents also strongly suggest that as important as heating control is, it is difficult for them to understand and many reported misusing heating.
In terms of sustainability, a surprising number of households reported that it was important and acceptable to them to heat their homes all year round, even in the summer, and almost threequarters of respondents in UK, Italy, and Germany admitted to opening windows in the middle of winter to let in fresh air (but letting heat out). Other very common practices included heating every room, even those that are unoccupied; overheating for pets; and overheating to wear summer clothing in the winter. Some respondents even seriously discussed heating to turn their bum red, to heat socks, and to give their boilers fond names such as "baby." Our evidence reveals also that heating practices can not only empower households with warmth, but culminate in conflict, with possible tensions with landlords but also other family members, guests, and even neighbors.
In terms of temperature settings, our respondents reported demanding a huge range of temperatures which also fluctuate widely across households and winter and summer seasons. While roughly 60% of respondents reported a narrower range of heat between 20 and 22 degrees in the winter, another 40% reported preferences far outside this range, some as high as 30, others as low as 2. Moreover, most respondents (more than half) reported being satisfied to very satisfied with their existing heating systems, perhaps creating a tractable barrier to change. That said, others reported deficient and defunct heating systems that were so bad they literally started fires, or heating so unreliable people had to cope by sitting in heated cars in the winter or stockpiling extra boilers around the house.
In terms of desirability of change, some respondents (about one-third) stated they would prefer switching to solar and slightly less to natural gas, but other options such as hydrogen or electric heat were poorly rated and ranked. And, while respondents reported a large range in their willingness to pay for low-carbon heat, these findings were inconsistent and unreliable, ranging from €0 (a very common answer) to €99,999 per month (perhaps indicating low-carbon solutions have perceived infinite value). If households were going to adopt low-carbon heat, the survey suggests that reliability and ease of use in particular are the highest preferred. Whatever engineers or designers do to make heating systems "smarter" should first and foremost be concerned with making them easy to use and reliable. Adding to the complexity of the systems as a matter of making them "smarter" is against the highest preference of the energy users who want more reliable and easy to use systems. Respondents lastly reported being not very well informed or supportive about emerging business models such as heat as a service or P2P trading; none of these were strongly supported or supported by more than about a quarter of respondents. The most trustworthy entities identified by the survey were not traditional media, friends, or scientists, but perhaps oddly technology suppliers and professional technicians.
In terms of country variation, our evidence suggests that the Germans are far more likely than others to heat all year round. Italians express a preference more than others for heating every room, whereas Spanish respondents report prioritizing monetary savings. Swedish households are more likely to overheat their homes for pets, and British households report much cooler temperatures than other countries. These elements underscore perhaps the cultural elements of heat.
Our findings suggest that the decisions made about heating, space cooling, and hot water are not always purposively rational. Ongoing actions, preferences, and practices about household heat are seamlessly interconnected with technologies but also demographic attributes, complex goals, myopic preferences and a host of unsustainable behaviors. The decisions made about heat far extend beyond solely economic self-interest, logic, rationality or even a desire to save the planet and reduce emissions. Some households seem to care very much about their heat, are knowledgeable about its sources, strongly adamant in their preferences, and firm in their temperature settings. Others seem to care less, to even put heat to use to play practical jokes (making roommates sweat in the summer, inducing cold water while someone is showering), or they have very low self-reported literature or a wide and waffling array of temperature preferences.
This great variety of heating literacy, practices, preferences and priorities offers a very strong critique towards attempts to push the sector towards decarbonisation by applying "one-sizefits-all" policy options, e.g. a carbon tax, or a particular technology, e.g. a heat pump or a boiler, which would be unlikely to satisfy all stated preferences within our survey at all stated times and seasons. This complexity suggests that the decarbonisation of household heat is a co-evolutionary and dynamic process that transcends markets and infrastructures-being both shaped by them but also shaping their diffusion. Our survey results show how household literacy (or lack of it), experience, trust and wasteful practices may be just as important to many households as design of a heating system technology or how many tons of carbon it may displace. Policy and research must come to accept this myopia if it is ever to make further progress at decarbonizing the European heating sector.