Home battery payback calculator
Home battery payback calculator: an honest estimate of whether — and when — a storage battery pays for itself. It accounts for round-trip efficiency, degradation and cycle life, which most calculators ignore and so overstate the returns.
Runs in your browser — nothing is uploaded to a server
Store surplus solar and use it in the evening instead of buying from the grid.
How much energy the battery actually delivers per cycle.
What the energy you put into the battery costs you.
How to use it
Pick a mode
With solar panels (store surplus) or a time-of-use tariff (arbitrage).
Enter capacity, cost and the price gap
Usable battery capacity, install cost and the high/low price per kWh.
Open “more parameters”
Round-trip efficiency, degradation, cycle life and rebate — for an honest projection over the whole lifespan.
Why it's useful
The real question about a battery isn't “how much does it cost” but “will it pay off, and when”. That depends on the price gap the battery captures, charge/discharge losses and how long it lasts. A wrong assumption easily turns “worth it” into “losing money”.
Most calculators overstate returns by 25–40% because they ignore round-trip efficiency, degradation and the cycle-life ceiling. We compute it honestly: value per kWh = efficiency × high price − low price, accumulated over the full lifespan (warranty or cycle life, whichever comes first), and we show the cost per kWh from the battery — if it's above your price gap, the battery won't pay off.
It works both with solar (self-consumption) and without it (day-night arbitrage), and answers honestly whether a battery makes sense in your case and how long it takes to pay back.
FAQ
It depends on the price gap it captures, its cost and its lifespan. Payback is often 8–15 years, and sometimes a battery never pays off within its life — the calculator shows this honestly.