A detached house in the Striesen district of Dresden (built in 2015, KfW 70 standard) was developed into a modern, energy-efficient overall system in several stages. Despite the originally installed gas condensing boiler and existing underfloor heating, the focus was on a sustainable conversion of the energy supply.
In 2020, a 7.4 kWp photovoltaic system with an east-west orientation was installed on the flat roof for around €10,000 net - combined with a wallbox for future electromobility. With the purchase of an electric car in 2021, the system could be optimally utilised: Thanks to intelligent energy management, self-consumption of around 70 % is now achieved. Of around 5,000 kWh of annual PV generation, around 3,500 kWh is used directly in the household.
Another important step was taken in 2024 with the conversion of the heating supply: The gas heating was replaced by a modern heat pump. Previously, gas consumption was around 16,000 kWh per year, which resulted in costs of around 2,500 euros. The use of the heat pump reduces the energy requirement to around 25 %, corresponding to around 4,000 kWh of electricity per year. Around 1,000 kWh of this is covered by an existing photovoltaic system. This reduces the annual costs for the heat supply to around 1,000 euros.
The system is supplemented by a separate domestic hot water heat pump in the basement. This utilises the moderate temperatures inside the building all year round (over 10 °C) to provide hot water particularly efficiently.
The advantage of this concept is that the main heat pump for the underfloor heating can be smaller and therefore works more efficiently and cost-effectively - especially in winter, as the energy-intensive hot water preparation is outsourced.
This project shows how the intelligent combination of photovoltaics, electromobility and heat pump technology can sustainably optimise even comparatively young buildings - with a high self-consumption rate, reduced energy costs and a significantly improved environmental footprint.
