Sump pumps are one of the most important backup loads because outages often happen during storms when they are needed most.
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Quick Answer
Most sump pumps use 500 to 1,500 running watts and can surge much higher at startup. Outage-day kWh can range from very low to several kWh.
Backup-Power Focus
Size for both surge and expected wet-weather runtime. Dry-day averages are not enough for resilience planning.
Typical Backup Ranges
| Pump Size | Running Watts | Starting Watts | 24h Outage kWh |
|---|---|---|---|
| 1/3 HP | 500 - 800 W | 1,200 - 2,200 W | 0.1 - 1.8 |
| 1/2 HP | 700 - 1,100 W | 1,600 - 3,000 W | 0.2 - 2.8 |
| 3/4 HP | 900 - 1,400 W | 2,200 - 3,800 W | 0.4 - 4.0 |
Practical Example
At 1,000 W for 2.5 total hours during an outage, daily energy is 2.5 kWh.
Related: What Size Generator for Sump Pump.
FAQs
Why do sump pumps trip small inverters?
Startup inrush can exceed inverter surge limits.
Is battery-only backup enough?
Depends on storm-day runtime and available usable kWh.
Should I test backup monthly?
Yes, regular testing reduces failure risk.
CTA
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