How much wattage does a dual fuel generator lose on propane?

Answered by RV Parts Giant · Upland, CA · October 31, 2026

Short answer: About 10%. Every dual fuel generator we list that publishes both figures drops 9 to 11% on propane, such as 2,200 to 1,980 running watts on the Westinghouse iGen2800DFc. Size the generator on its propane running watts if propane is the fuel you plan to use.

Here are the running and peak figures from our listings. All but the WEN are Westinghouse. The percentage is our own arithmetic.

Model	Gas running	Propane running	Running loss	Gas peak	Propane peak
iGen2550DFc	1,900 W	1,700 W	10.5%	2,550 W	2,300 W
iGen2800DFc	2,200 W	1,980 W	10%	2,800 W	2,520 W
iGen4000DFc / iGen4000DFcv	3,300 W	2,970 W	10%	4,000 W	3,600 W
iGen5000DFcv	3,900 W	3,500 W	10.3%	5,000 W	4,500 W
WGen5300DFcv	5,300 W	4,800 W	9.4%	6,500 W	5,800 W
WEN DF480iX	4,000 W	3,600 W	10%	4,800 W	4,320 W

Why it can change which model you buy

Say your load adds up to 2,000 running watts:

iGen2550DFc: too small on either fuel (1,900 W gas, 1,700 W propane).
iGen2800DFc: fine on gas (2,200 W), short on propane (1,980 W).
iGen4000DFc: fine on both, with room left over.

So someone who runs only on gas could buy the 2800, while someone who wants propane for the whole trip needs to step up. Run the same check on your own load, using the running column, not the peak.

Models that do not publish a propane figure

Some dual fuel listings we carry give one rating only:

Champion dual fuel models (2,500 W, 4,500 W, 4,750 W, 5,300 W, 6,500 W and 7,850 W starting) do not label the number by fuel on our listing.
DEWALT 2,700 W, WEN DF360iX and WEN DF680iX label their rating as gas, with no propane figure.
DuroMax HX, Firman 4,125 W, Generac iQ 3,800 W, WEN 5,600 W and WEN DF280iX give one rating without naming a fuel.

We would not assume those lose exactly 10%. Check the rating plate or manual, or ask us, and treat the rated figure as the gas number until you have seen it.

Before you switch fuels

Our listings do not state propane runtime for the models in the table. The Generac iQ is the one that does, at up to 16 hours on a 20 lb LP tank against up to 13 hours on gasoline. The runtime hours listed for the iGen range are at 25% load and do not name a fuel, so don't plan a trip around them on propane. Run any of these generators outdoors only.