Battery retrofit economics
Solar Battery Retrofit Payback Calculator — Test Storage Economics
Estimate simple payback for adding battery storage to an existing solar installation using annual self-consumption gains, avoided grid purchases and export-value changes.
Retrofit economics
USD
kWh
kWh/year
%
USD/kWh
USD/kWh
USD/year
years
Simple payback is a screening metric. Financing, taxes, degradation, replacement, tariff changes and battery operating constraints can materially change project economics.
Enter retrofit cost and annual battery value assumptions.
How battery retrofit payback works
The calculation treats each shifted kilowatt-hour as replacing an electricity purchase at the avoided-grid value while recognizing that the same energy may have been exported at a lower value without the battery.
Delivered energy = shifted solar × efficiency
Annual gross benefit = delivered energy × avoided grid value − shifted solar × export value
Simple payback = installed cost ÷ (gross benefit − annual operating cost)
Annual gross benefit = delivered energy × avoided grid value − shifted solar × export value
Simple payback = installed cost ÷ (gross benefit − annual operating cost)
Why retrofit economics are site-specific
The battery may increase self-consumption, reduce peak purchases, provide backup or relieve export constraints. This calculator monetizes only the entered energy-value pathway.