What size home battery do I need?

Two questions drive it: what you want to back up (and for how long), and whether you'll add solar.

As a rough feel, a ~20 kWh battery keeps the essentials — fridge, lights, Wi-Fi, a window AC — running about 10–14 hours. Heavy loads like central AC, an electric range, or an electric water heater need a bigger system. The analyzer gives you a starting range from your real usage; you set the final size around what you want to keep running.

More: what size you need to cover a Rate 7 peak, and how much solar a battery can actually use.