Solar Electricity Storage - Independence Calculator
Annual electricity consumption:
Information about the Independence Calculator
With the independence calculator you can estimate the self-consumption rate and
degree of self-sufficiency for a typical photovoltaic system with battery storage on a single family
house in Germany. Real values can differ up to more than 10% from the calculated results depending on the location and
In the diagram you can also see how much electricity is fed into the grid, taken from the grid, consumed directly or
the amount that flows over the battery.
Influence of Photovoltaic Power
Influence of Battery Capacity
Influence of Electricity Demand
Annual Electricity Demand
Enter your annual electricity demand here. The average annual electricity demand of a single family house in Germany
is about 4000 kWh. The lower the annual electricity demand, the higher the achievable degree of self-sufficiency.
Here you should define the size of the photovoltaic system (nominal power of the photovoltaic modules). For 1 kWp
photovoltaic power you need a roof area of about 5 to 10 m². The higher the photovoltaic power,
the higher the achievable degree of self-sufficiency.
The battery size is defined by the useable battery capacity. The useable capacity of a battery storage is usually lower
than the nominal capacity and should be given in the data sheet of the battery manufacturer.
The higher the battery capacity, the higher the self-consumption rate and the degree of self-sufficiency.
The self-consumption rate describes the share of the generated solar electricity that is either simultaneously consumed
or used for battery charging. If the self-consumption rate rises the amount of solar electricity that is fed into the grid decreases.
The degree of self-sufficiency describes the share of the electricity consumption that is covered by the photovoltaic
storage system either by simultaneous consumption of the generated solar electricity or by discharge of the battery.
If the degree of self-sufficiency increases the amount of electricity from the grid decreases.
The independence calculator was developed by the Solar Storage Systems
research group of Prof. Volker Quaschning at the HTW Berlin.
Special thanks go to Johannes Weniger, Tjarko Tjaden, Joseph Bergner und Martin Hofmann.
Further background information on the calculations can be found
The related project was funded by the Environmental Relief Program (UEP II)
that is co-financed by the European Union through the European Regional Development
Fund (ERDF) and the state of Berlin.