How big should your home battery be?
Battery size for your solar system and heat pump running cost against gas, worked out hour by hour with public data and your own figures.
How big should your solar battery be: calculator
Consumption, kWp, yield per kWp and orientation: how self-consumption and self-sufficiency grow with battery capacity, and where the curve flattens.
The calculator gives estimates, not measurements: it works out one year hour by hour with a standard load profile and a PVGIS weather year, scaled to your figures.
You will need:
- electricity used in a year, in kWh
- size of the solar system in kWp
- annual yield per kWp and orientation
Other calculators
Guides
- The "1 kWh of battery per 1,000 kWh" rule: what the sums say
- Heat pump: how much electricity price and boiler matter
- JAZ, SCOP and COP: which number to use for a heat pump
- Method and sources: profiles, assumptions and what we leave out
- Self-consumption and self-sufficiency: two numbers, kWh by kWh
- South-facing or east-west roof: self-consumption and battery
- Usable capacity, nominal capacity and efficiency of a battery
How we work
Public data, with sources
BDEW load profile, PVGIS weather year, HTW Berlin and Fraunhofer ISE measurements: every figure with a link and a date.
Not yet measured by us
We have not measured batteries or heat pumps ourselves, and we say so on every page.
A calculation, not advice
Energy and running costs, not returns, incentives or installation advice; advertising sits apart from the result.
Method and sources: profiles, assumptions and what we leave out