Home BackupJune 3, 2026
How Much Home Battery Storage Do You Need? A Sizing Guide
Short answer: The average US home uses 30 kWh per day. For 24h backup of critical loads (fridge, lights, router, phone charging) you need 8-12 kWh. For whole-home backup you need 25-35 kWh. For solar self-consumption optimization, 10-15 kWh covers most households.
Sizing by Goal
| Goal | Recommended capacity | Typical system | Installed cost |
|---|---|---|---|
| Critical load backup (24h) | 8-12 kWh | 2x Enphase IQ 5P | $10,000-$15,000 |
| Whole-home backup (24h) | 25-35 kWh | 2x Powerwall 3 | $25,000-$35,000 |
| Solar self-consumption | 10-15 kWh | Powerwall 3 or Franklin aPower | $12,000-$18,000 |
| Off-grid cabin | 30-60 kWh | Multiple batteries + inverter | $30,000-$60,000 |
The Simple Formula
Add up your critical appliances’ daily consumption: refrigerator (~1.5 kWh/day), lights (~0.5 kWh), router/TV (~0.5 kWh), phone charging (~0.1 kWh). Multiply by backup days needed, then add 20% buffer for inverter efficiency losses. For 24h critical load backup: (1.5+0.5+0.5+0.1) × 1 × 1.2 = 3.1 kWh minimum. Round up to the nearest available system size — a 5 kWh Enphase unit gives you solid margin.
Home Battery Systems
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