A home battery can provide backup power, shift energy between tariff periods, and increase the usefulness of solar, but the right decision depends on the job you need it to do. Start with essential loads and outage duration, then compare equipment, installation, tariff, warranty, and resilience assumptions.
Define the purpose
Backup for lights and refrigeration is a different requirement from whole-home backup, bill shifting, or avoiding export limits. Write down the goal before comparing battery sizes or prices.
Estimate essential energy
Multiply essential load by expected outage duration. A 1 kW essential load for six hours needs about 6 kWh delivered before reserve, inverter limits, and efficiency losses. Starting surges require a separate power check.
Compare the financial case
Use installed cost, usable capacity, tariff spread, export credit, cycles, degradation, maintenance, financing, incentives, and replacement timing. A resilience benefit may be valuable even when bill savings alone produce a long payback.
Verify the system
Confirm backup hardware, supported circuits, islanding behavior, transfer equipment, electrical capacity, warranty limits, and local approvals with the manufacturer, utility, and qualified installer.
Sources
The figures and rules in this guide are checked against:
- Solar Integration: Solar Energy and Storage Basics — U.S. Department of Energy
- Residential Clean Energy Credit — Internal Revenue Service
- Electricity Explained: Energy Storage for Electricity Generation — U.S. Energy Information Administration
- Energy Storage Systems (safety) — National Fire Protection Association