Home Battery Buying & Ownership Guide
What to know about compatibility, runtime, maintenance, warranties, and portable “solar generators” before choosing a battery system.
Solar and Battery Compatibility
- Adding battery backup is not simply a matter of attaching a battery. The solar inverter, battery, system controller or gateway, electrical configuration, and existing equipment must be compatible with backup operation.
- During an outage, a properly configured system disconnects the home from the utility grid so it can safely run on stored and solar energy.
- Existing solar owners should have an installer verify compatibility before selecting a battery system.
Estimating Runtime
Runtime depends primarily on
- Usable battery capacity in kWh
- Average electrical load in kW
- Which circuits are being powered
- Whether solar is producing energy during the outage
Simple planning relationship
Approximate runtime = usable battery capacity ÷ average electrical load
For example, a 13.5 kWh battery at about 1 kW is roughly 13 hours before reserve and system losses. Actual runtime changes with usable capacity, reserve settings, conversion losses, appliance cycling, weather, and solar production.
Ownership, Lifespan, and Warranties
Home batteries generally require little routine homeowner maintenance compared with engine generators.
Battery capacity gradually declines with age and use.
Warranty terms vary by manufacturer.
For context only — not recommendations. Current major systems include:
- Tesla Powerwall: 13.5 kWh and a 10-year limited warranty.
- Enphase IQ Battery 5P: 5.0 kWh usable capacity and warranty terms up to 15 years / 6,000 cycles depending on conditions.