Home Battery Storage Savings Calculator

About this calculator

A home battery earns its keep through arbitrage: it charges from cheap off-peak or overnight electricity, then discharges that stored energy during expensive peak-rate hours, so the annual saving equals the daily kWh cycled through the battery, multiplied by its round-trip efficiency (typically 85-95%, since some energy is lost in charging and discharging) and by the difference between the peak and off-peak price, summed over the year's cycles. Payback period is simply the installed battery cost divided by that annual saving.

Homeowners on time-of-use electricity tariffs run this calculation before buying a home battery system, because the economics depend heavily on how wide the gap is between their cheapest and most expensive rate — a large day/night price spread can pay back a battery in a few years, while a narrow spread can stretch payback well beyond the battery's warrantied lifespan.

This calculator takes your battery size, round-trip efficiency, expected daily cycles and your day and night electricity prices and returns your estimated annual savings and payback period, so you can judge whether a battery makes financial sense on your specific tariff before you buy one.