What Size Generator Do You Need to Run a Submersible Pump?
By the Generator Size Calculator Team · Updated · 5 min read
Quick answer: Honda lists a small submersible water pump at 200 running and 400 starting watts and a centrifugal-type submersible at 500 and 650. A 1,000-watt inverter runs the small pump, and a 2,000-watt inverter the centrifugal one. For flood cleanup with a pump, a dehumidifier and lights, a 2,500-watt generator is a comfortable size. Keep the generator dry and outdoors, and use GFCI protection.
Submersible pump watts
| Pump | Running watts | Starting watts |
|---|---|---|
| Submersible water pump, small, 400 gph | 200 | 400 |
| Submersible pump, centrifugal type | 500 | 650 |
| Sump pump, 1/3 HP | 750 | 1,500 |
| Sump pump, 1/2 HP | 1,000 | 2,100 |
These are Honda's typical figures. The sump pump rows are for comparison, since a sump pump is a bigger motor with a bigger surge. See what size generator a sump pump needs.
Which generator size to choose
| Pump | Generator for the pump alone |
|---|---|
| Small submersible (200 / 400 W) | 1,000 W inverter |
| Centrifugal submersible (500 / 650 W) | 2,000 W inverter |
A typical 2,000-watt inverter delivers about 1,600 running watts, which is plenty for either pump with room for lights. A 1,000-watt unit delivers about 800 running watts, which suits the small pump. Check your pump's label, since a larger pump will draw more.
Example: pump, dehumidifier and lights
| Load | Running watts |
|---|---|
| Submersible pump, centrifugal type | 500 |
| Dehumidifier | 650 |
| Lights, chargers | 175 |
| Running total | 1,325 |
The largest extra start-up load is 150 watts (the pump's 650 minus 500, and the dehumidifier's 800 minus 650), so the peak is about 1,475 watts. A 2,000-watt inverter's 80% mark is about 1,280 watts, just under the running total, so a 2,500-watt generator is the safer size, with an 80% mark of 2,000 watts and about 3,125 starting watts.
Include a fan, lights and anything else.
Wet-work safety
- Keep the generator outdoors and dry, on a raised, level spot, not in floodwater. See can you run a generator in the rain.
- Use GFCI protection and outdoor-rated cords, and keep plugs out of standing water.
- Turn off the power at the panel and do not wade into water that may touch live wiring. If in doubt, call an electrician.
Run the generator outdoors, at least 20 feet from doors, windows and vents. Never in a garage or shed, even with the door open. Never run one in a flooded basement. See how far a generator should be from your house.
Frequently asked questions
How many watts does a submersible pump use?
Honda lists a small submersible water pump at about 200 running and 400 starting watts, and a centrifugal-type submersible at 500 and 650.
Can a 1000-watt generator run a submersible pump?
The small one, yes. A 500-watt centrifugal pump fits a 1,000-watt inverter on paper, but a 2,000-watt unit leaves room for lights.
What size generator runs a pump and a dehumidifier?
About 2,500 watts for a 500-watt centrifugal pump, a dehumidifier and lights.
Is a submersible pump the same as a sump pump?
Both sit in water, but a sump pump is usually a bigger motor with a larger start-up surge. See the sump pump guide.
Is it safe to run electrical equipment in a flooded area?
Only with GFCI protection and with the power to the building off, and not if wiring may be in the water. If unsure, ask an electrician.
Related calculators
Sources: Running and starting watts from the Honda generator wattage guide (submersible water pumps, sump pumps, dehumidifier). Generator sizes apply the 80% running rule and an assumed starting capacity about 25% above the running rating. The lights and chargers in the example are assumed values.