How big should my home battery be?
Roughly as big as what you have left over during the day on an ordinary day and use again in the evening and at night. Bigger is not automatically better: you use the extra kWh on fewer days, while you do pay for them.
A battery only earns from electricity that actually goes in and out. Two things determine which size fits: how much solar power you have left over during the day, and how much you use in the evening and at night. The smaller of the two is the limit; anything above it stays unused on most days.
Summer and winter
In summer you often have more left over than a battery can absorb, in winter often almost nothing. A battery that fills up every day in summer has little to do in winter. So look at a whole year, not at one sunny day.
With a dynamic contract
With a dynamic contract a battery can also charge when electricity is cheap and discharge when it is expensive. Then a bigger battery can earn more, also in winter. How much depends on the difference between cheap and expensive hours, and that is uncertain.
Power counts too
Besides the capacity (kWh), the power (kW) counts: how fast the battery can charge and discharge. A battery with little power does not fully cover the hob or the tumble dryer; the rest then comes from the grid.
Calculating it
The calculator works through every hour of a year and shows, per battery size, what it yields and when it pays for itself. That way you can see whether a bigger battery adds anything for you.
Calculate which battery size suits you
An estimate, not personal advice. How the calculator works: How does this calculator work?
Other questions
- Does a home battery pay off?
- What changes when net metering ends?
- Do solar panels still pay off without net metering?
- Fixed or dynamic contract: which is cheaper?
- What is a dynamic energy contract?
- Is a dynamic contract smart with solar panels?
- How do I compare dynamic energy contracts?
- What are the risks of a dynamic contract?
- Does a dynamic contract pay off with an electric car?
- What are feed-in costs?
- What will the end of net metering cost me?
- Should I cancel my fixed contract before net metering ends?
- Does a home battery make sense without solar panels?
- Should I switch off my solar panels when power prices are negative?
- Does it pay to charge the electric car on solar power?
- Does a heat pump suit a dynamic contract?
- How do I read my annual electricity statement?
- What is a feed-in tariff?
- How much of my solar power do I use myself?
- Battery, charger, heat pump or another contract: what first?
- Does a home battery make sense with a fixed contract?
- Plug-in battery or fixed home battery?
- How much energy does a home battery lose?
- Is electricity cheap at night with a dynamic contract?
- What does a home battery do in winter?
- How much electricity do I use at night?
- Does a home battery suit a heat pump?
- Which energy comparison site can I trust?
- How do I calculate the payback time of a home battery?
- What do time-dependent network tariffs mean for me?