Photovoltaic self-consumption with a heat pump

With a heat pump, you can use more of your own solar power yourself, especially for hot water. In the depths of winter, however, PV only covers a small portion.

According to klimaaktiv, heat pumps and photovoltaics go together very well. Because the heat pump turns one kilowatt hour of electricity into at least three kilowatt hours of heat, the benefit of your self-generated electricity is multiplied.

Realistic expectations

In winter, when the heat pump runs the most, the PV system delivers the least. According to the klimaaktiv Wegweiser guide, you can only expect around 1 kWh per kWp of installed capacity on an average December day. In the depths of winter, solar power therefore only covers a small part, with the rest coming from the grid. In the transitional periods and in summer, especially for domestic hot water, things look much better.

Storing as heat instead of in batteries

• According to the guide, a 300-litre domestic hot water cylinder can store around 9 kWh of heat. The heat pump needs around 2 to 3 kWh of electricity for this.
• The screed of an underfloor heating system also acts as a storage medium.
• In the sunnier months, heating water is a more economical option than a battery storage system, according to the guide.

Practical tips

• Schedule hot water production for the early afternoon; according to klimaaktiv, this increases self-consumption.
• With intelligent control, the share of self-consumption can be increased by about a fifth, according to the guide. To do this, look out for an interface such as SG-Ready.
• For detached houses with a heat pump, klimaaktiv recommends economical PV sizes between 5 and 10 kWp.

All terms · Heat pump knowledge