Real vs nameplate battery capacity

A battery advertised as “10 kWh” rarely delivers 10 kWh to your loads. Depth of discharge, temperature and round-trip losses all take a cut. Enter the nameplate figure to see what you actually get — the physics the financial comparison sites skip.

Why nameplate ≠ usable

Three deductions stand between the label and your appliances. Depth of discharge: you can only safely use part of the capacity — about 80% for LiFePO4, 50% for lead-acid — or you destroy cycle life. Temperature: capacity drops in the cold, sharply for lead-acid. Round-trip efficiency: some energy is lost charging and discharging, about 4% for LiFePO4 and up to 20% for flooded lead-acid. A “10 kWh” lead-acid battery in a cold space can deliver less than 4 kWh.

Comparison and payback portals usually treat the battery as a flat kWh number, which overstates what you really get. Size and compare on delivered energy instead. For honest payback grounded in this real figure, see the battery payback calculator.

Educational estimate. See the methodology for the constants and formula.