Using photovoltaics, energy storage and heat pumps for your own energy transition

Editorial team: Mr Wiedmer, what motivated you to invest in renewable energies? 

Siegbert Wiedmer: My motivation, of course, was to use the new heating system to improve the future energy balance of the building – especially with regard to the CO2 taxes we can expect to have to pay in the future. Furthermore, we were looking for an investment that would also yield a "profit". Our "profit" is the costs that will no longer be incurred in the future because with the new heating system we won't buy in any gas and we'll buy much less electricity. Thanks to renewable energy, we also won't be faced with any CO2 taxes.

Editorial team: Together with your wife, in 2021 you converted your home to a supply of electricity and heat delivered by renewable energies using photovoltaics, an energy storage unit and a heat pump. The decision to make this change will certainly have been a long while in the making. Can you explain it in a little more detail? 

Siegbert Wiedmer: The initial spark came from our electrician. He had already installed many photovoltaic systems with KOSTAL components, including some combined with heat pumps, and had only good things to report. After our initial conversations, I looked into the topic in more depth, read about other people’s experiences and even took part in a webinar. After that, the decision was obvious.

Editorial team: Right from the start, you designed your solar system with an energy storage unit and heat pump for high self-consumption. What role does the Renewable Energies Act subsidy play for you in terms of the economic viability of your solar system?

Siegbert Wiedmer: The Renewable Energies Act subsidy obviously has a role to play in a system of this power class. Especially in the months between April and September, because during this time we don't consume all the electricity we generate ourselves. Our system sometimes supplies over 100 kilowatt hours for several days. However, the motivation for switching to renewable energy was the ability to consume the power we generate as two households.

Editorial team: Energy storage units are vitally important to a high degree of self-sufficiency. What has your own experience been here?

Siegbert Wiedmer: It was clear to me that we would definitely need a storage unit. This is the only way we can consume a lot of the electricity ourselves. This has also been demonstrated in practice over the past few months – we've already enjoyed four months of 99 % self-sufficiency over the eight months of PV operation.

Editorial team: Why did you choose the KOSTAL inverter, BYD storage unit and heat pump? With KOSTAL you can choose from a wide range of compatible storage systems.

Siegbert Wiedmer: In tests, KOSTAL proved to me the very high level of efficiency of the BYD storage unit. I also know from our installer that KOSTAL inverters work perfectly in combination with heat pumps and storage units.

Editorial team: You have just under 13 kilowatt hours of storage capacity. What are your experiences of this?

Siegbert Wiedmer: In the months between May and September, the storage unit is easily sufficient. In the other months, the capacity is sufficient on very good sunny days. When the sky is overcast and the heat pump is running, we only draw from the grid what the solar system does not supply.

Editorial team: Do you use the KOSTAL Solar App and if so, what do you think of it?

Siegbert Wiedmer: Yes, of course. It's clearly laid out and reliably provides me with data that is relevant to me and that I need for efficient system operation.