Outage planning guides
Sump Pump Backup Plan
A sump pump can be a critical outage load because the highest water risk often arrives with the same storm that interrupts power.
Use this guide for basement flood-risk planning when a sump pump must run through rain, snowmelt, or storm recovery.
Suggested loads
| Load | Watts | Priority | Note |
|---|---|---|---|
| Primary sump pump | 400-1,200 running watts | critical | Startup surge can be significantly higher than running watts. |
| Battery backup pump charger | 50-300 watts | critical | Some systems charge batteries separately from pump operation. |
| Water alarm | Battery powered | useful | Alerts can help catch failures early if someone is home. |
| Basement light | 8-20 watts | useful | Low-watt lighting helps inspection without major energy use. |
| Dehumidifier | 300-700 watts | optional | Usually not a first-priority outage load during active pumping needs. |
Planning steps
- Find the pump horsepower or measured running watts.
- Estimate how often the pump cycles during heavy rain.
- Size the backup for surge output and watt-hours, not one number alone.
- Plan for longer runtime if water continues entering after rain stops.
- Test alarms and backup equipment before storm season.
Example plan
- Duration
- 12 hours
- Estimated energy
- 1,000-5,000 Wh depending on pump size and cycle frequency
- Battery note
- A dedicated sump backup battery or large power station should be evaluated by pump surge, runtime, and expected cycle rate.
- Generator note
- A generator can power a sump pump if it handles surge and is safely positioned outside, but starting it during severe weather may not be practical.
- Solar note
- Solar is usually secondary for sump planning because heavy rain and nighttime pumping can coincide with low production.
Mistakes to avoid
- Sizing from running watts while ignoring motor startup surge.
- Assuming a short outage when rainwater may keep flowing for hours.
- Placing backup equipment where rising water could reach it.
- Treating a dehumidifier as more important than the pump during active flooding risk.
Safety and limits
- Do not enter standing water around electrical equipment.
- Keep cords and backup units away from wet areas where possible.
- This guide is not plumbing or electrical installation advice.
FAQ
How big of a battery do I need for a sump pump?
It depends on pump watts, startup surge, and how often it cycles. Heavy rain can require several kWh, while light cycling may need much less.
Can solar back up a sump pump?
Solar can recharge batteries in good sun, but sump pumps often need power during storms or at night, so battery capacity and surge rating matter first.
Related calculators
Generator Wattage CalculatorEstimate running watts, starting surge, and a practical generator size for selected backup loads.Portable Power Station Runtime CalculatorEstimate how long a portable power station can run a load after efficiency losses and reserve.Home Outage Backup PlannerPlan 24, 48, or 72 hour backup needs for critical home loads using battery and generator estimates.