The use of space heating and cooling differs between regions and is greatly influenced by temperature and humidity. In areas with cold weather, such as central and northern Europe, space heating prevails. Due to high temperatures throughout the year in India, cooling requirements dominate. In some countries, such as the United States and China, the need for space heating and cooling is almost equivalent and varies from region to region.

Heating degree days (HDDs) and cooling degree days (CDDs) try to capture weather-induced space heating and cooling needs by comparing the outside temperature with a reference value, which varies regionally and depends on the population’s comfort temperature. If, for example, the temperature falls below the reference value (e.g. 16°C), the resulting HDDs are the difference between the reference and the actual temperatures.

Depending on each country’s technology mix for heating and cooling, the yearly fluctuation of weather can considerably affect electricity consumption. For example, France experienced milder weather during 2020 compared to 2019 (HDDs down 8% and CDDs down 6%), which has been reflected in lower power demand for heating and cooling. Meanwhile, Spain had a warmer summer (CDDs up 3%), resulting in increased electricity demand for cooling. A warmer winter in the United States resulted in a drop of 10% in the number of HDDs, and subsequently lower electricity demand for heating in some regions. In South Africa, Australia and Brazil the greatest difference from 2019 was observed during the summer season, where lower temperatures led to a drop in CDDs of 15% (South Africa and Australia) and 10% (Brazil).

In addition to yearly weather variations, long-term trends are influencing heating and cooling demand. This can, for example, be observed in Europe, where increasing temperatures resulted in a drop of 17% in population-weighted average HDDs and an increase of 96% in CDDs between 1980 and 2017.

Annual electricity consumption for heating and cooling depends not only on the weather, but also on the mix of technologies. For example, although Germany was 35% colder than France in 2018, only 4% of its electricity demand was heating related, while in France it was 18% – this is due to the higher share of electricity in total energy use for space heating in France compared to Germany (15% and 2% respectively). This is also reflected in the higher electricity consumption per HDD per person in France than in Germany. In northern Europe, Sweden had one of the highest shares of electricity demand for heating in 2018 (23%), driven by the cold weather in Scandinavian countries and the high share of electric heating (26%).

In contrast to heating, for which a variety of fuels are deployed, electricity is the predominant energy source for cooling – but the distribution and type of appliances varies significantly. In California, which experienced a very hot summer in 2020 (CDDs up 35%), more than 16% of electricity consumption could be attributed to cooling – almost twice the share of in 2019. Although average temperatures in India are much higher than in California (with 4.2 times the number of CDDs in 2020), only 3% of electricity was used for cooling in 2019. This means that India used only 1.7% of the electricity used per person per CDD in California, due to lower access to cooling appliances and the frequent use of fans instead of air conditioners. This illustrates the large potential for increasing electricity demand for cooling in India.

Electric heating and cooling systems have a large potential for demand response by supporting the balancing of demand and supply. In systems with a large share of renewables, they can help to avoid curtailment, stabilise the grid and reduce the need for storage deployment.