Quick answer: A 2,000 to 2,300-watt portable inverter generator — the DuroMax XP2300iH (best overall, dual fuel), the Westinghouse iGen2200 (quietest, cleanest power), or the Champion 100692 (best value) — covers the real starting-watt surge of a typical 1/3 to 1/2 HP sump pump, not just its running watts. Unlike a battery backup, a generator needs someone to physically start it, so it is a second layer for a multi-day outage, not a replacement for automatic backup power — and it must always run outdoors, never in a garage or basement.
A generator is the backup-power option every sump pump buying guide assumes you already understand, and most don’t explain well: it is the only backup on this site with no automatic switch-on and no finite charge to run down, because it burns fuel instead of stored power. That makes it the right tool for an outage that drags into day two or three, when a battery backup has already drained and a water-powered backup isn’t an option on your well water. This guide covers sizing it correctly — most buyers under-size for the startup surge, not the running load — and the picks worth buying.
Our top picks at a glance
| Generator | Best for | Running / starting watts | Fuel | Price |
|---|---|---|---|---|
| DuroMax XP2300iH | Best overall | 1,800W / 2,300W | Gas or propane | ~$479–699 |
| Westinghouse iGen2200 | Quietest / cleanest power | 1,800W / 2,200W | Gas | ~$500–600 |
| Champion 100692 | Best value | 1,700W / 2,000W | Gas | ~$340–450 |
All three are inverter generators, not conventional open-frame units — inverter models deliver cleaner, more stable sine-wave power, which matters for the pump’s switch and float controls and for anything else you plug in during the same outage.
1. DuroMax XP2300iH — Best Overall
DuroMax XP2300iH
- Runs on gasoline or propane — real flexibility during an extended outage, when gas stations can be down too and a propane tank already in the garage still works.
- 2,300 starting watts comfortably covers a 1/2 HP sump pump's roughly 2,150-watt surge, with room left for a sump alarm or a few lights on the same circuit.
- Built-in CO Alert shuts the unit down if carbon monoxide builds up around it — a real safety feature, not a substitute for running it outdoors.
- 3-year warranty.
The dual-fuel capability is the reason this is the overall pick: during a multi-day storm outage, gasoline supply gets unreliable fast, but a propane tank sitting unused by the grill keeps the pump running. A flooding basement will not wait on a fuel shortage — a free 30-day Amazon Prime trial gets a replacement cord, fuel stabilizer, or a spare pump to the door in two days if something else in the setup fails mid-storm.
2. Westinghouse iGen2200 — Quietest, Cleanest Power
Westinghouse iGen2200
- Pure sine wave output with low total harmonic distortion — the cleanest power of the three picks, easiest on a pump's electronic float switch.
- 2,200 starting watts, enough for a 1/2 HP pump with a small margin left over.
- Runs quieter than conventional generators at comparable output, which matters if the generator sits near a bedroom window during an overnight outage.
- Gasoline only — no propane option, unlike the XP2300iH.
Pick this one if noise is a real constraint — a generator running all night outside a window is a legitimate reason some homeowners default to a battery backup instead, and a quieter unit narrows that gap.
3. Champion 100692 — Best Value
Champion 100692
- 2,000 starting watts still clears a 1/3 HP pump's roughly 1,300-watt surge with real margin, and a 1/2 HP pump's with less margin — check your pump's nameplate HP first.
- Ultralight design, under 50 lbs, easiest of the three to carry out and set up during a storm.
- 4.6-star average across thousands of Amazon reviews and a 3-year warranty.
- Least headroom of the three picks if you plan to run anything beyond the pump itself.
The right pick if the generator’s only job is keeping one pump running — it has no spare capacity for much else, but it does that one job for meaningfully less money.
Sizing: why starting watts matter more than running watts
A motor’s rated running wattage is not what it draws for the first fraction of a second. According to sizing guidance from electrical-safety resources, an induction motor like the one in a sump pump can briefly draw three to four times its running wattage just to overcome the resistance of starting from a dead stop. A 1/3 HP pump that runs on roughly 800 watts can surge toward 1,300 watts on startup; a 1/2 HP pump that runs around 1,050 watts can briefly draw 2,000 to 2,150 watts. A generator sized only to the running number will bog down, trip its breaker, or stall the instant the float switch triggers and the motor kicks on — often during the storm, on the one try that matters. All three picks above are sized with that surge in mind, not just the running load printed on the pump’s nameplate.
The manual-start tradeoff — and why it still matters
Every other backup-power option on this site turns on by itself. A battery backup and a water-powered backup both activate automatically the moment the primary pump can’t keep up or the power cuts out — no one has to be present. A generator does not. Someone has to go outside, start it, and connect it, which means it does nothing for a basement flooding while the house is empty or everyone is asleep. That is the real reason a generator is a second layer, not a first line of defense: pair it with a battery backup for the first few automatic hours, then start the generator once you’re up and the outage looks like it will run long.
And it must run outdoors. According to the U.S. Consumer Product Safety Commission, portable generators run too close to a home — in a garage, on a porch, even near an open window or door — have been linked to hundreds of carbon monoxide deaths, frequently during storm-driven outages when a generator is running overnight and a window gets left cracked for the exhaust. Run it at least 20 feet from the house, pointed away from any door, window, or vent, every time.
Getting the power to the pump
For a single pump, the simplest path is a heavy-duty outdoor-rated extension cord sized for the pump’s amperage, run from the generator directly to the pump’s plug — no electrician, no panel work. If you plan to power more than the pump — a few lights, the refrigerator, a furnace blower — a manual transfer switch or interlock kit wired into the panel by a licensed electrician is worth the cost, since it lets you select circuits from inside the house instead of running a cord to every device during a storm.
The bottom line
The DuroMax XP2300iH is the generator we’d buy for most sump pump setups, since its dual-fuel flexibility matters most exactly when an outage runs long enough to need a generator at all. The Westinghouse iGen2200 is the better pick if a quiet overnight generator matters more than fuel flexibility, and the Champion 100692 covers a single pump for less money with less headroom. Whichever you buy, size it to your pump’s starting watts, not the running number on the label, and treat it as the second layer behind a battery backup that switches on while you’re still asleep.