What exactly is meant by ‘power-to-heat'?

While a rising share of the electricity we use in our homes comes from solar, wind and other forms of renewable energy, our heating systems often still run on natural gas. This is bound to change. ‘Power-to-heat’ shows how renewables can also be used for heating.

Illustration: Erneuerbare Energien und Stromnetz unter einer Lupe© BMWi

It's all about getting more out of renewable energy

More renewables, less fossil fuels. In 2015, solar, wind and other forms of renewable energy accounted for almost one third of Germany’s electricity, setting a new record. By 2025, the share of renewables in our electricity supply is to reach 45 per cent. However, renewables are not only becoming more relevant for generating electricity, but also for heating. In the context of the energy transition, solar, biomass and ambient heat are slowly but surely taking over in the heating sector, while fossil fuels are gradually being phased out. This is good news for the environment.

Using electricity from renewable sources to generate electricity

How can we use electricity from renewable sources to generate electricity? This is where ‘power-to-heat’ comes in. Power-to-heat technologies have been on the market for quite some time now, with heat pumps being the most important one. Heat pumps use electricity to extract heat from the ground, compress it and then use it to run the heating system. What is great about capturing energy from the external environment is that for every kilowatt-hour of electricity required to run the heat pump, several kilowatt-hours of heat can be generated. So if you want to convert power into heat, heat pumps are definitely the way to go. However, they are only efficient at lower temperatures.

Whenever very high temperatures are needed – for example in industry – electrode boilers are used. Electrode boilers consist of huge tanks in which water is boiled directly. In contrast to immersion heaters, which use heating elements to generate energy, electrode boilers use electrodes and salt water. Electrode boilers directly convert renewable energy into heat. However, for every kilowatt-hour of electricity required to run the boiler, only just under one kilowatt-hour of heat will be generated.

How power-to-heat can help drive forward the energy transition

Power-to-heat technologies offer major potential to drive forward the energy transition. By converting electricity into heat, these technologies help raise the share of renewable energy in the heating sector. If renewable electricity is used to run power-to-heat systems, this also helps protect the climate and reduces the use of fossil energy sources.

Converting electricity into heat can also help stabilise the grids. Power-to-heat technologies can be combined with heat storage units and programmed to absorb electricity from the grid at times when a lot of electricity is being generated – for example when there is a lot of sun or wind. At times when the amount of electricity that is being generated is low, heat storage units can help overcome temporary shortages. Large heat storage units that are connected to heat networks can supply heat for longer time periods.

Reducing energy consumption, increasing the share of renewable energy

There are some power-to-heat technologies that are especially promising. High quality, high efficiency heat pumps can reduce energy consumption in buildings – in particular those that are already energy efficient – and also help raise the share of renewable energy. If heat pumps are combined with a good heat storage unit, this can make them even more efficient. So power-to-heat combines the use of electricity from the grid with the generation of renewable energy. This ensures that we can make the most of every kilowatt-hour that is generated in Germany.

Research for the energy transition

There are many exciting research projects under way in the area of power-to-heat. These are supported by the Federal Ministry for Economic Affairs and Energy and the Federal Ministry of Education and Research as part of the 6th Energy Research Programme. More information on ideas, projects and results, can be found here.

You can also receive funding for using renewable energy in your home

The Federal Ministry for Economic Affairs and Energy is also lending a hand to consumers who want to switch to using renewable heat in their homes. The ‘Market Incentive Programme for Renewable Energy on the Heating Market’ (MAP) offers attractive funding to customers – for example for buying a heat pump, which is currently the most efficient power-to-heat technology. Companies and municipalities can also benefit from this programme. More information can be found here.