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How long can a portable generator run without stopping?
Updated
On gasoline, a portable generator runs until the tank is empty, then it has to stop. The makers of the five picks here claim 10 to 18 hours per tank, at loads they did not state in the parts we read. You must shut it off and let it cool before you refuel, so nonstop running for days is not something a gasoline portable can do.
What the makers claim per tank
- Westinghouse iGen5000DF18 hours
- Westinghouse WGen5300DFcv14.5 hours
- Westinghouse WGen9500DF12 hours
- Champion 4000-Watt10 hours
- WEN 56235i10 hours
These are "up to" numbers. Makers usually measure them at a light load. Run the generator harder and the hours drop fast. We break the claims down further in propane and runtime.
What a full day costs in fuel
Here is each claim turned into gallons for 24 hours. Treat it as the best case.
| Generator | Claim | Tank | Gallons per 24 hours at that rate |
|---|---|---|---|
| WGen9500DF | Up to 12 hours | 6.6 gal | 13.2 |
| WGen5300DFcv | Up to 14.5 hours | 4.7 gal | 7.8 |
| iGen5000DF | Up to 18 hours | 3.4 gal | 4.5 |
| Champion 4000-Watt | Up to 10 hours | 1.54 gal | 3.7 |
| WEN 56235i | 10 hours (spec table) | 1 gal | 2.4 |
A three day outage on the big open-frame unit is about 40 gallons at the best-case rate. That is a lot of gasoline to store safely and to find when stations have no power either.
The real limits
- Refueling. The Red Cross says to turn the generator off and let it cool before refueling. Gasoline on a hot engine can catch fire. Plan on a break at every tank.
- Oil. Small engines need oil checks and changes on a schedule set in hours, and a long outage burns through those hours fast. If a manual calls for a change every 100 hours, that is about 4 days of round-the-clock use. Read your manual for the real number. The WGen9500DF and WGen5300DFcv list automatic low oil shutdown.
- Load. Planning to use 80 percent or less of running watts keeps the engine cooler and stretches each tank. The wattage calculator sizes for that.
Propane runs longer between stops
On a dual-fuel unit, runtime on propane depends on the tank you hook up, not the small built-in gas tank. The Champion 4000-Watt Dual Fuel claims up to 25 hours on propane. The caveat: the part of the listing we read did not say what size tank or what load that assumes, and you give up about 10 percent of your running watts on propane.
You do not have to run it all night
Many people run the generator in blocks. A few hours to cool the refrigerator and freezer down, charge phones and run the furnace, then off. A closed refrigerator holds its cold for a while. That saves fuel and gives the engine its breaks. If you do run overnight, the placement rules matter most while everyone is asleep: 20 feet out, exhaust away, CO alarms working. Compare the picks on the roundup page.
Safety first, every time
- Carbon monoxide kills. Never run a generator indoors, in a garage, in a shed or on a porch, even with the door open. Keep it at least 20 feet from the house. Point the exhaust away from windows, doors and vents. Put battery CO alarms inside your home.
- Never backfeed. Do not plug a generator into a wall outlet or dryer outlet. It can kill a utility worker or a neighbor and can start a fire. To power home circuits you need a transfer switch or an interlock kit, installed by a licensed electrician.
- Without that, run heavy-duty outdoor extension cords from the generator straight to each appliance.
- Let the engine cool before you refuel. Store fuel outside the house.