Heat pumps are among the most important climate-friendly heating technologies of the future. To be particularly emission-free, they must use renewable electricity, such as solar power from the rooftop or green power from the grid. Heat pumps can also help use the power grids efficiently. When there is a lot of wind and solar power in the grid, they switch on. When little renewable energy is available or the load is too high, they reduce their performance. A market overview.
Heat pumps use geothermal heat, ground water or ambient air as a heat source. Using electricity, the systems are highly efficient at raising the temperature of the ambient energy, producing heat for heating and hot water with low carbon emissions. In a building with a normal energy standard, heat pumps can use one kilowatt hour of electricity to turn environmental heat into 3–4 kWh worth of heat – almost like a perpetuum mobile.
The technology is becoming more climate-friendly every year. The share of electricity from photovoltaics and wind turbines in the power grid is growing – in Germany, green power currently amounts to around 50 percent. The goal is to reach 80 percent by 2030. It is particularly advantageous from an ecological and financial perspective if the heat pump also uses solar power from your own photovoltaic installation.
Many homeowners have discovered the benefits of heat pumps by now, so sales are skyrocketing in Europe: In 2022, the sales volume of heat pumps in the EU rose by around 40 percent to three million devices. A sharp increase is seen in Poland, the Czech Republic and the Netherlands. Most of the systems are installed in Scandinavia.
From a technical point of view, using solar power from your own rooftop to power the heat pump is quite easy. For communication between photovoltaic systems and heat pumps, there are several options on the market: On the side of the heat pump, the SG-ready input serves as an interface. SG stands for “smart grid”. Most heat pumps have had this interface for a couple of years now. It can be controlled via the inverter of the solar installation, an energy management system or a smart metering system (smart meter for short).
As the heat pump’s electricity demand is not fully covered by the photovoltaic installation, the power grid supplies it when needed. When it does, it should contribute to the grid’s stability as much as possible. This requirement is a result of the energy transition: The growing share of renewable energies – largely solar and wind energy – is leading to strong fluctuations in power generation, so power consumption must be adjusted accordingly. One promising approach to balancing power supply and demand is to turn specific electrical loads on or off. Heat pumps can play an important role here. Ideally, grid-supplied power should be consumed when the share of renewables is high. When there is little available or the load is too high, the heat pump could be curtailed for some time.
“Controllable heat pumps could play an important role in stabilizing the grid and using the fluctuating supply of solar and wind energy more efficiently.” Dr. Jann Binder, Center for Solar Energy and Hydrogen Research Baden-Württemberg ZSW.
Heat pumps can also be controlled via the SG-ready interface to stabilize the grid. In Germany, this interface is even required if you want to receive subsidies for your heat pump. According to the subsidy guidelines, heat pumps must be able to react to control signals from the grid operator. During periods of high or low feed-in from renewable energy sources, heat pumps could run in such a way that they stabilize the grid. The most populous country of the EU intends to make this a reality soon. From 2024, distribution grid operators will have the option to control heat pumps and charging stations in order to avoid outages due to overloading local power lines. It will not be allowed to turn them off completely, only to temporarily reduce the amount of power they draw from the grid.
Grid-serving integration of heat pumps is already being tested in the east and north of Germany. Heat pump manufacturer Viessmann and transmission system operator 50Hertz are involved in this project. Grid operators can reduce the performance of heat pumps in households within their distribution area whenever necessary in order to stabilize the grid. However, it will be ensured that the temperatures in the heat storage and in the rooms don’t drop below a certain point, the project partners assured. No one should have to compromise on comfort. In return, customers will receive flexibility premiums for reducing the output of their heat pump.
The Center for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) is also working on climate-friendly heat generators that help stabilize the grid. Because if the number of heat pumps continues to grow and they are not properly adjusted, the power distribution grids could become overloaded. To prevent this from happening, researchers from Stuttgart have developed algorithms that reduce peak loads. They have tested this new method in Sweden where heat pumps are already widely used and winters are particularly cold. The result: The algorithms help to use the heat pumps more efficiently and in a way that keeps the grid stable. The load on transformers in the distribution grid was reduced by 10 percent.
Manufacturers are also promoting intelligent linking of heat pumps and power grids. For example ÖkoFEN from Austria: The GreenFox heat pump has access to a database with live electricity forecasts for individual countries. The forecasts show how “green” the electricity in the grid is at any given time. If electricity from coal-fired power plants is used, the heat pump reacts and shifts its standard heating times to a greener period. It heats primarily when it can use low-carbon electricity. This type of load management with heat pumps helps balance fluctuating generation and consumption in our future energy system.
In Europe, some electricity suppliers are already able to control heat pumps. And what about dynamic tariffs? Utility companies use them to pass on price fluctuations at the energy exchange to the consumer. If the renewable share in the energy mix is high and the price is low, the power is used for heating. If the opposite is the case, heat generation is postponed to a cheaper time of the day. From 2025, all electricity suppliers in Germany are obligated to offer such variable electricity tariffs.
Pioneers in this market segment are companies such as Tibber from Norway. According to the company, heat pumps from a growing number of brands can be integrated and controlled using Tibber’s app. Heat generation is modulated by an autopilot that ensures the house uses as little energy as possible, taking into account the weather forecast, electricity prices and conditions inside the house. Another example is aWATTar, a subsidiary of the Munich-based company tado. aWATTar shifts consumption to times of the day when the electricity is green or cheap. All dynamic electricity tariffs require a smart metering system.
Conclusion: Heat pumps are becoming smarter at heating. Not only do they use as much solar power from your rooftop and green electricity from the grid as possible – these climate-friendly heat generators can now even be used to help stabilize the grid, making use of excess power from renewable energy systems and cutting costs for the consumer. Grid operators, heat pump manufacturers, utilities and research institutes are working to make rapid progress.
