How many watts does a sump pump use?

Updated 2026-10-31 · Sources linked inline

A typical residential sump pump uses roughly 500 to 1,050 watts while running and needs about 1,000 to 2,150 watts for a moment at startup, depending on horsepower. Honda and Champion both publish figures by size. Sump pumps matter because the storms that knock out power are often the ones that fill the pit.

How this guide was made: this is a research guide built on manufacturer specifications and federal guidance, with sources linked throughout. We haven't bench-tested any of the equipment mentioned, and we don't claim to.

Published wattage by horsepower

Honda's chart flags sump pumps in its "240V required" column, so check your own pump's voltage on its label; many home pumps plug into a standard 120 V outlet. "Start extra" is starting watts minus running watts, the number the standard sizing method adds.

These are approximations from the generator makers, not measurements of your pump. A pump in a clean pit with a short vertical lift draws less than one lifting water a long way, or one working against a clogged check valve. Treat the range as the planning envelope.

Estimate from the label

Amps × volts = maximum running draw. A pump labeled 9.5 A at 120 V is about 1,140 W at most. Compare that to the table: it falls near the upper end for a 1/2 hp pump. Starting watts aren't on the label. For generator sizing, use the published start figures above.

How often does it actually run?

The running watts apply only while the pump is on. A sump pump cycles: water rises to the float, the pump runs for seconds to a couple of minutes, then rests. That duty cycle decides your energy use, so nobody can state a universal daily number.

Hypothetical example, labeled as an assumption: a 1/3 hp pump at 800 W that runs 3 minutes every 10 minutes during heavy inflow is on 30% of the time. Average power is 800 × 0.30 = 240 W, so 240 W × 24 h = 5.76 kWh per day. In a light drip, it might run 1 minute an hour, which averages about 13 W (800 × 1/60). The number of cycles per hour is what matters. If you want your own number, time a few cycles during a storm or after pouring water into the pit.

Sizing a generator for the pump

Use the generator size calculator method: running watts of everything on, plus the largest start extra.

Pump alone, using Honda's figures:

For a single motor, the standard and conservative methods give the same starting figure.

Pump plus fridge (Honda ENERGY STAR 192 W running, 1,200 W starting, 1,008 W start extra):

• 1/3 hp: running 800 + 192 = 992 W. The fridge's start extra (1,008) is larger than the pump's (500), so standard start = 992 + 1,008 = 2,000 W. Conservative: 992 + 1,300 = 2,292 W.
• 1/2 hp: running 1,050 + 192 = 1,242 W. Pump's start extra (1,100) is larger than the fridge's, so standard start = 1,242 + 1,100 = 2,342 W. Conservative: 1,242 + 2,150 = 3,392 W.

For the whole list, see what size generator to run a house and refrigerator generator sizing. A typical inverter generator rated around 1,800 W continuous and 2,200 W maximum fits a 1/3 hp pump by itself, a 1/3 hp pump plus fridge on the standard method (2,000 W) and not the 1/2 hp pump plus fridge conservative case (3,392 W). Check your actual generator's spec sheet.

Extension cords and the outlet

• Use a heavy-duty outdoor extension cord with a rating above the pump's draw. Keep it as short as the generator placement allows, undamaged and fully uncoiled.
• Plug the pump directly into the generator or a GFCI-protected outlet or cord, not a power strip. Sump pits are wet and shock risk is real; this is our advice, not a rule quoted from the sources.
• Never backfeed through a wall outlet. CPSC calls it extremely dangerous and a danger to utility workers (CPSC).
• Run the generator outdoors, more than 20 feet from openings. A basement pump is not a reason to put the generator in the garage. See generator carbon monoxide safety.

Options for backup power

Plenty of homeowners combine them. This is where generator vs power station helps with the tradeoffs.

Power station math for a pump

Runtime = battery watt-hours × 0.85 (efficiency assumption, same as our power station runtime calculator) ÷ average load in watts.

Example with an EcoFlow DELTA 2, which EcoFlow lists at 1,024 Wh (EcoFlow):

Those are arithmetic for assumed duty cycles, not measured runtime. They show why heavy rain breaks small batteries: the pump runs most when the battery is needed most. The start surge also matters. The DELTA 2 has a rated AC output, and a pump's starting watts (1,300 W for 1/3 hp per Honda) must fit within what the unit can deliver on a motor start. Check the manufacturer's surge spec, and try the setup with your own pump before you rely on it.

Test it before the storm

1. Check the pump runs when you lift the float, or pour water into the pit until it starts.
2. Plug it into the generator or power station and repeat. A pump that starts on the grid might trip a marginal source.
3. Verify the discharge line and check valve work and the water goes where it should.
4. Time a cycle and note it.
5. Check the generator's fuel, or battery's charge, and cord. Do it in daylight.

Alabama Power's storm safety page covers the broader outage-safety side (Alabama Power). Our Alabama outage checklist puts the steps in order.

Why the outage and the flood arrive together

In Alabama the weather that cuts power is often the weather that fills the pit. Alabama Power lists flooding as a year-round hazard, and thunderstorms, tropical systems and winter storms can all bring heavy rain along with outages (Alabama Power). If you have a sump pump, "the power is out" and "the pump is needed" are usually the same event, which is why the backup plan matters more than the pump's wattage.

Three practical consequences:

• Decide before the storm whether the pump is on your must-run list. For most homes with a pit, it belongs on that list because it runs only when needed and protects the house.
• Keep the generator or battery ready before the rain starts. A pit can fill within hours in a heavy storm, and you don't want to set up in the dark.
• Consider a high-water alarm that runs on a battery, so you know if the pump stops for any reason (our suggestion).

Summary

Add your pump to the appliance wattage chart numbers, use the sizing calculator with a meter reading, and keep a spare plan for the day it rains for 24 hours.