Seasonal performance factor (SPF)
The seasonal performance factor shows how much heat your heat pump delivers over the entire year per kilowatt-hour of electricity. It is the most important key figure.
- Additional electricity consumption compared to a 35 °C flow temperature, calculated at 2 to 2.5 % per degree.
- At a 55 °C flow temperature, the heat pump needs around 40 to 50 % more electricity for the same heat.
The seasonal performance factor (SPF) is the ratio of the heat your heat pump generates in a year for heating and hot water to the electricity it needs for this. According to klimaaktiv, an SPF of 4 means: 1 kWh of electricity is turned into 4 kWh of heat, 3 kWh of which come from the environment.
Why this is important for your house
The SPF determines your electricity costs. klimaaktiv calculates: with an SPF of 4 instead of 3, annual electricity costs fall by a quarter, and usually over 20 years. Unlike the COP from the test bench, the SPF takes into account all operating conditions of a year at your location.
Which values are realistic
- In practice, according to klimaaktiv, SPFs between 3 and 4.5 are achievable for heating and hot water. Optimised systems in detached houses can achieve up to 5 for heating operation.
- klimaaktiv recommends aiming for an SPF of at least 3. The Wegweiser (guide) for installers specifies a target value of at least 4 for the overall system in the planning stage.
- The biggest lever is a low flow temperature.
How to determine it
In the planning stage, the installer calculates the SPF. During operation, you divide the amount of heat generated in a year by the electricity consumption in the same period. For this, you need a heat meter and a separate electricity meter. Our heat pump calculator provides a first assessment.
Related terms
COP (coefficient of performance)SCOP (seasonal coefficient of performance)Flow temperatureHeat meter
Sources
- klimaaktiv: So läuft Ihre Wärmepumpe rund. Tipps für die Planung und Installation (klimaaktiv: How to Keep Your Heat Pump Running Smoothly. Tips for Planning and Installation, BMK, 2024) (accessed on 4 October 2026)
- klimaaktiv Wegweiser zur guten Installation von Wärmepumpen (klimaaktiv Guide to Good Installation of Heat Pumps, BMK, 2020) (accessed on 4 October 2026)