How much battery storage and backup time might this budget support?

How it works

Understand the estimate

Divide your budget by the assumed cost per kWh to estimate rated battery capacity. Multiply by the usable percentage, then divide by the average power needed by your appliances to estimate hours of backup.

Make it more accurate

Battery losses, inverter limits, start-up power, battery type and warranty limits all affect backup time.

The starting figures are examples. Replace them with the rates or prices that apply to you.

Usable capacity and runtime are not the same

Battery labels often state nominal energy capacity. A depth-of-discharge setting, inverter efficiency and minimum reserve can reduce energy available to your appliances. Backup time depends on how much power your appliances use at the same time.

Example: For a nominal 5 kWh battery limited to 80% usable discharge, roughly 4 kWh is available before inverter losses. At a continuous 0.5 kW load, the estimated backup time would be eight hours; a 2 kW load reduces it to two hours.

Before relying on the estimate

An appliance may need more power to start than the inverter can supply, even when the battery still has charge. Check both kilowatt output and kilowatt-hour capacity.

For more detail, read our calculation and editorial standards. Use your own bill, receipt or quote for current prices. These tools do not fetch live rates.