Home batteries are the most misunderstood piece of the electrification stack. Here's how to figure out if one belongs in your home — and if so, how big.
If you've lost power multiple times this year, and particularly if you've lost food, lost work time, or had to evacuate, this is the strongest use case. Value the battery as insurance, not as an investment.
Typical sizing: 5-13 kWh. You don't need to power the whole house — just refrigeration, basic lighting, routers, medical equipment, and well pumps.
If your utility pays you $0.04/kWh for solar exports but you buy power at $0.25/kWh, a battery lets you shift your own solar from day to evening. This is now a real investment case in California, Hawaii, and parts of Arizona.
Typical sizing: 10-20 kWh (to cover evening/night consumption).
If your utility has peak rates > $0.35/kWh and off-peak < $0.12/kWh, you can charge off-peak and discharge during peak. Payback 8-12 years without solar. With solar, much faster.
LFP (Lithium Iron Phosphate) is now dominant for stationary storage: safer, longer cycle life (5,000+ cycles), lower energy density (doesn't matter at home). Tesla Powerwall 3, Franklin Home Power, and most new entrants are LFP.
Avoid: NMC-chemistry systems marketed as "home" products — they're a 2018-era design.