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Home Heating in Belgium | v1.2 | energy.at-site.be | August 2022

Can solar or wind renewables cope with heating loads in Belgium?

Short answer: no, unless for houses or flats that only need a tiny amount of heating energy.

Motivation: find out how solar (and wind) energy production match with typical household energy consumption in Belgium.

Solar energy production is often compared with household electricity consumption. At higher latitude this comparison is not accurate. Most solar energy is generated in summer and most household energy consumption is in winter. Also electricity is only a part of household energy. We illustrate this for Belgium - at a latitude of 50 degrees - in following parts:

The data shows that heating is a challenge both due to the magnitude of required energy and the production/demand mismatch with solar energy.

1. Household energy consumption in Belgium

Table 1 shows the end-user energy for Belgium from 2017 to 2020, as provided by Eurostat[1]. This includes home applications and does not include transportation. Clearly space heating is the biggest part, using almost three quarters of the yearly household energy. This is slightly more than the EU average of 63.6% for space heating due to the northern location and buildings with a low insulation level. In Belgium, household energy uses approximately a quarter of final energy over a year[2]. Household electricity use is over five times less, at 4.81 percent of total final energy in 2018 in Belgium [2]. Hence, comparing renewable energy potential savings relative to household electricity consumption is misleading; since household electricity consumption only corresponds to a minor part of total energy demand. In this text we use data from 2018 from table 1, since there is not much difference with more recent values for Belgium.

Table 1. Energy end-use for households in Belgium, 2017..2020. Data source - Eurostat[1]
Household final energy shareSpace heatingSpace coolingWater heatingCookingLighting and appliancesOthers
Belgium 201773.8%0.1%11.4%1.7%12.7%0.4%
Belgium 201873.5%0.1%11.9%1.7%12.5%0.9%
Belgium 201973.2%0.1%11.9%1.7%12.8%0.4%
Belgium 202072.7%0.1%11.7%1.7%13.2%0.6%

2. Solar energy production mismatch with household heating

Due to the high latitude of Belgium, more solar energy is generated in summer than winter, and more space heating is needed in winter than in summer. This is shown in figure 1. We model solar production and space heating demand as follows:

Figure 1. Belgium - monthly percentage of solar, wind, heating and cooling degree days (year is 100%).

For the months January, February, November and December the average heating degree days are about 61 percent, while solar generation is 11.7 percent of the yearly total. For wind power about 43.2 percent of energy is produced in these months, which is better matched to winter heating energy demand.

Other models also point to a production/demand mismatch between solar and heating:

Table 2. Forecast renewable energy and heating degree days in Jan, Feb, Nov and Dec in Belgium, as a percentage of a year (year is 100%). Data source: elia.be - open grid data - CC BY 4.0 [10]

ItemAverage 2013-20192019201820172016201520142013
Onshore wind45.8%40.6%46.8%38.6%45.9%47.8%54.0%44.8%
Offshore wind42.3%39.4%45.6%40.5%43.4%45.8%49.1%39.9%
(1) HDD = heating degree days with a balance point of 15.5 degrees Celsius, as obtained from Wolfram alpha for the EBBR weather station

Based on these models we find that space heating demand is about 4 to 5 times larger in winter than what is produced by solar. And taking into account the space heating is the dominant energy consumer it is clear that there is a significant mismatch between solar energy production and household energy consumption.

3. Using renewables for a small heating load in Belgium

To illustrate the impact of the solar heating demand mismatch we consider the average natural gas consumption of a typical household ; 23.260 kWh when gas heating is used [11]. This load is significant, corresponding to 10 kWh of energy per heating degree day (Figure 1). In Belgium the maximum residential rooftop solar capacity is restricted to 10 kWpeak. This capacity is not sufficient to heat a home directly with electric space heaters. We can argue that additional insulation or a heat-pump can reduce this. To keep our analysis simple we assume a heat pump with a constant COP (coefficient of performance) of four, resulting in a heating load of 2.5 kWh per degree day.

This assumption is a simplification which is more benign for solar than in reality, as shown in the work of G. Emmi et al. [12]:

Using these assumptions we obtain a yearly heating energy demand of 5,840 kWh, one fourth of an average home in Belgium due to the assumption of a COP of four. Next we opt to overdimension the available solar and wind energy to 10 kWpeak. Combining this with the Renewables ninja data from Figure 1 we obtain yearly energy values as shown in Table 3. Ranging from about 1.75 times to 3.92 times the required energy for heating.

Table 3. Produced yearly energy for wind/solar mixes of 10 kWpeak of energy. Data source - renewables.ninja - bias corrected solar and wind data - CC BY-NC 4.0 [3][4]

Energy mixkWh/year for 10 kWpeakyearly kWh surplus
100% solar10,200 kWh/y4360 kWh
75% solar, 25% wind13,400 kWh/y7560 kWh
50% solar, 50% wind16,600 kWh/y10760 kWh
25% solar, 75% wind19,700 kWh/y13860 kWh
100% wind22,900 kWh/y17060 kWh

Figure 2 shows a box plot of the energy surplus of produced daily energy for different energy mixes, with daily heating load subtracted. For solar we see that the average and medium surplus are negative for solar in the months November, December, January and February, even with a yearly surplus of 10,200 - 5,840 = 4360 kWh. Hence we can conclude that solar energy is not suitable for heating in these four cold months. Opting for 10 kWpeak into a mix of 75% solar and 25% wind improves the averages significantly, and this continues to improve until 100% wind. Still, even as 100% wind has a large surplus, insufficient energy is available about 25% of the days in the period from November till February.

Figure 2. Energy surplus in Belgium for different solar and wind energy mixes under a heating load and assuming ideal daily energy storage.
Belgium low heating load

Another representation of wind and solar fluctuations is shown in Figure 3, without considering heating load. This shows daily data from Elia for the monitored capacity by in Belgium for January 2020[10]. The lack of solar energy is easy to understand, since it has the highest peak capacity (3887 MegaWatt-peak) and lowest amount of produced energy (81.7 GWh). Offshore and onshore wind produce much more energy even though they have a lower peak capacity. Still significant time-spans with low energy production can exist, as for example the period from 20 to 25 January. Heating demand cannot be time shifted for such long periods, so either energy storage or backup power is needed.

Figure 3. Wind and solar energy fluctuations in January 2020 for Belgium.

We observe that solar power is insufficient for the considered small heating load. Reducing the heating load or increasing installed solar power can help, still the production/demand mismatch will continue to exist in these cases. Specifically a large energy surplus of solar in summer and a tight solar surplus in winter. Another possibility is seasonal storage for solar. Still at present there do not seem to be viable solutions, as detailed in[13]. Even a 1,250 kWh battery at 100 Euro/kWh would result in a cost of 125,000 Euro storage cost, which is not viable. Using power to gas can result in a lower storage cost, still for heating application it will be favorable to use power to gas first for wind which is better matched with the heating load.

4. Household heating energy mix in Belgium

In previous parts we considered relative comparisons to illustrate production/demand mismatch between solar and heating, as well as seasonal fluctuations for a single home use case. In this section we show absolute energy numbers for household and heating energy. The next tables summarizes the energy mix for space heating. Table 4 shows that fossil fuels account for over 85 percent of total heating energy. In the category renewables and bio-fuels, using wood is the largest energy source for heating. So over 95 percent of heating results in direct CO2 emissions.

Table 4. Energy mix for space heating of households in Belgium, 2017/2018. Data source - Eurostat [1]
Space heating fuel sourceElectricityOil and petroleumNatural gasSolid fossil fuelsRenewables and bio-fuelsDerived heat
Belgium 20173.2%38.0%47.4%1.4%10.1%0.0%
Belgium 20183.2%37.9%47.1%1.2%10.4%0.3%
Belgium 20203.0%41.5%44.1%0.6%10.5%0.2%

Table 5 shows the percentage used for heating per household energy source, and also quantifies household and heating energy in TeraWatt-hour (TWh). We see that about 12 percent of electricity is used for space heating, whereas about 89 percent of all other household energy sources are used for heating. Total heat energy for households in Belgium corresponds to 69.2 TerraWatt-hour for the year 2018, over four times as much as the household electricity used for other purposes than space heating. About 60% of this energy, 41.5 TWh, is consumed in the months January, February, November and December. Assuming that this can be reduced with a factor four still results in about 10 TWh energy consumption in these months. Suppose that we want to generate 10 TWh with solar during summer and to store it for winter at a cost of 100 Euro per kWh then we need a storage investment of 1000 billion Euro.

Techniques that reduce heating footprint, such as better isolation for example, will be more cost effective than storing solar energy for winter. Cheaper storage solutions exist [13] but are less suited for seasonal storage of solar power:

Table 5. Energy mix summary of household energy in Belgium, 2018. Data source - Eurostat [1][2]
Belgium 2018Household percentageHousehold energyHeating energyPercentage used for heating
Electricity19.5%18.4 TWh2.21 TWh12.0%
Rest80.5%75.8 TWh67.1 TWh88.5%
  +Oil and petroleum  30.3%  28.5 TWh  26.2 TWh  92.0%
  +Natural gas  41.0%  38.6 TWh  32.6 TWh  84.4%
  +Solid fossil fuels  0.8%  0.8 TWh  0.8 TWh  100%
  +Renewables and biofuels  8.2%  7.68 TWh  7.2 TWh  93.7%
  +Derived heat  0.19%  0.18 TWh  0.18 TWh  100%
Total100%94.2 TWh69.2 TWh73.5%

5. Conclusion

For Belgium solar is not suitable for meeting typical household energy demand. Space heating consumes almost 75% of household energy and over 60% of heating energy demand is in the period of November till February. In this period solar produces only about 10% of its yearly energy and seasonal storage is not yet economical. Wind energy is better matched with heating demand in Belgium and heat-pumps can lower the energy demand. Still the amount of energy needed for household space heating is significant and space heating is also needed for companies, schools and hospitals for example. Hence efficient heating of buildings using other solutions than solar energy will be required to lower the carbon footprint in a meaningful way.

And what about other countries? Countries closer to the equator will in general require less space heating, and the seasonal fluctuations of solar power will be lower. For hotter countries space cooling may be needed instead. The inverse is true for countries further from the equator. There even less solar energy will be available in the heating season.

Acknowledgement: many thanks to:

Disclaimer: This work provides a summary of the original Eurostat energy data, converting ktoe (kilo ton oil equivalent) values to other energy units such as relative percentages and energy expressed as TeraWatt-hours (TWh). Values are rounded to 3 significant digits. Eurostat is not responsible for data conversion or rounding errors in doing so.


Energy consumption in households, edition 2020 - year 2018
Eurostat energy balance summary, edition January 2021 - year 2019
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Renewables.ninja simulator
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PVGIS 5.1 simulator
Countries in Europe, based on renewables.ninja data for years 2005-2015
Cities in Europe, based on PVGIS v5.1 data for years 2005-2015
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Energy storage - a cost, size and efficiency comparison


March 2023
version 1.3, extended table 1 with household consumption data for 2020
August 2022
version 1.2, minor, renamed page name from solar to heating; since this name is more appropriate for this text.
February 2022
version 1.1, updated references
November 2020
version 1.0, initial version
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