6 June 2026 · 4 min read
How many kWh of home battery do you need?
By Stefan Douw · Maker of Stekkerkompas
For most Dutch households with solar panels the useful size sits between 5 and 9 kWh. Bigger sounds better, but above a certain point each extra kWh pays itself back more and more slowly. The right size depends on your evening use and on how much solar you have left over.
Start with your evening and night use
A battery you fill with solar only earns something when it gives that power back in the evening and at night, when the panels produce nothing. An average household uses around 2,500 kWh per year, about 7 kWh per day. The part of that between roughly 18:00 and 08:00 sets how much storage you actually use. For many households that window falls between 3 and 6 kWh, so a 5 kWh battery already covers a large share.
Match it to your solar
A rule of thumb is about 1 to 1.5 kWh of battery per kWp of panels. A bigger battery only helps if there is surplus to fill it. In summer there is plenty, in winter barely any, so a large battery sits half empty for a good part of the year. Your panels therefore help set the ceiling on what is useful.
Why bigger is not always better
The self-consumption your battery delivers is bounded by your own use and by how often you can cycle it per day. Double the capacity and you do not double that self-consumption. The income from trading on the imbalance market also falls per kWh as the battery grows, through market saturation and because you cannot cycle a large battery fast enough. The result: each extra kWh earns less than the last, and the payback per kWh gets longer.
Watch power and connection too
Capacity (kWh) is how much the battery stores, power (kW) is how fast it charges and discharges. A plug-in battery on a normal socket is capped at about 800 watts. You only use a larger battery's full power with a dedicated group in the meter cabinet. That power, not just the capacity, also sets how much you can earn from trading.
Run the numbers
The calculator picks a battery size that fits your usage, panels and contract, and shows the point where extra kWh barely add anything. Run your own situation and compare a few sizes side by side.
Sources
Run the numbers for your home
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