16Jan
Battery Backup 101: How Many Circuits Can You Really Run?
Battery backup is amazing—until you try to run “the whole house” and learn what kWh really means. Let’s size this honestly.
Start with critical loads (not rooms)
Most homes pick a “keep life normal-ish” list:
- Refrigerator + a few kitchen outlets
- Internet/Wi-Fi + office
- Lights in key areas
- Garage door
- Medical devices
- Sump pump (if applicable)
The simple math behind runtime
- Batteries store energy in kWh
- Your loads consume energy in kW (or watts)
- Runtime ≈ battery usable kWh ÷ average load kW
- Big takeaway: a few heavy loads can shrink runtime dramatically.
Why a critical loads subpanel helps
A critical loads subpanel keeps backup clean and predictable:
- Only selected circuits run during outages
- Less chance of accidental overload
- Easier to manage priorities
Backup isn’t about “how many circuits.” It’s about which loads you can power—and for how long—without surprises.
Realistic expectations
- Lighting + fridge + Wi-Fi: very doable
- Electric heat, large AC, big cooking loads: possible, but requires bigger systems (and a budget check)
