On average, the sun shines more than 1,800 hours a year in Denmark.
In Denmark, the global solar irradiation is approximately 1,000 kWh/m2 per year measured horizontally and approximately 1,200 kWh/m2 measured on surfaces with a 45-degree gradient. Solar heating systems are usually capable of utilising about 500 kWh/m2 of the solar energy.
Like other renewable energy systems, solar heating systems are fairly expensive to acquire but inexpensive to operate compared with fossil fuels.
Most of the 30,000 or so solar heating systems in Denmark are installed in private homes. Solar energy is also used in large-scale systems (swimming baths, hotels, camping sites) with extensive hot-water use and in very large-scale collective systems connected to district heating plants. In these plants, solar energy is often used in combination with biomass such as wood pellets, wood chips and straw.
Solar heating is thus used primarily for heating water in hot-water tanks. Therefore, it is very simple to use with other energy sources in homes – be it natural gas, oil furnaces, fuel furnaces, heating pumps or electric heating. It is also possible to use solar heating systems for heating of homes, e.g. in the form of underfloor heating.
Use of solar energy as a primary source of heating (in these latitudes) suffers under the fact that the energy yield is highest at the time of year (summer) when we need it the least. However, it is not true that solar panels work only in the summer. A well-insulated solar panel will also provide a heat contribution on sunny winter days. Solar heating systems can generate electricity – even on cloudy days.