Dual fuel vs gas generator for home backup
For home backup, dual fuel is usually worth it. On the two Westinghouse generators sold both ways, the dual fuel version costs $50 to $60 more. Propane costs you about 10% to 11% of the running watts, but it keeps in a sealed tank without going stale, which matters for a generator that sits unused between storms.
Published , by Alex Rowan
We haven't tested these units ourselves. Watts, run times and storage advice come from the makers' store pages and manuals, fuel prices and energy content from the EIA, and every price shows the store and the day we checked it. Links go to the maker's or a retailer's store, and we don't earn anything from them. How we work.
The same generator, sold both ways
| Model | Fuel | On gasoline | On propane | Weight | Price |
|---|---|---|---|---|---|
| Westinghouse iGen2800c (opens in a new tab) | Gasoline only | 2,200 W running 2,800 W starting | No | 45 lb | $549 Westinghouse price, Oct 27, 2026, listed as out of stock |
| Westinghouse iGen2800DFc (opens in a new tab) | Dual fuel | 2,200 W running 2,800 W starting | 1,980 W running 2,520 W starting | 45 lb | $599 Westinghouse price, Oct 27, 2026, listed as out of stock |
| Westinghouse iGen4000c (opens in a new tab) | Gasoline only | 3,300 W running 4,000 W starting | No | 61.7 lb | $799 Westinghouse price, Oct 27, 2026, listed as out of stock |
| Westinghouse iGen4000DFc (opens in a new tab) | Dual fuel | 3,300 W running 4,000 W starting | Not published | 62.8 lb | $859 Westinghouse price, Oct 27, 2026, listed as out of stock |
All four are Westinghouse inverters, priced at Westinghouse's own store, which showed them as out of stock on the day we checked. Each pair has the same engine, tank and gasoline output. Westinghouse doesn't publish the iGen4000DFc's output on propane.
How much power you lose on propane
| Model | Running, gasoline | Running, propane | Running watts lost | Starting, gasoline | Starting, propane |
|---|---|---|---|---|---|
| Westinghouse iGen2800DFc (opens in a new tab) | 2,200 W | 1,980 W | 10% | 2,800 W | 2,520 W |
| Champion 201319 (opens in a new tab) | 3,500 W | 3,150 W | 10% | 4,500 W | 4,500 W |
| Westinghouse iGen5000DFc EFI (opens in a new tab) | 3,900 W | 3,500 W | 10% | 5,000 W | 4,500 W |
| Westinghouse WGen3600DFv (opens in a new tab) | 3,600 W | 3,240 W | 10% | 4,650 W | 4,180 W |
| Westinghouse WGen9500DFc (opens in a new tab) | 9,500 W | 8,500 W | 11% | 12,500 W | 11,200 W |
Every dual fuel model here loses about a tenth of its running watts on propane. The Champion 201319 is the exception on starting watts: Champion rates it at 4,500 W starting on either fuel. If you plan to run on propane, size the generator against its propane rating, which is lower than the gasoline one.
Run time and fuel cost
A 20 lb tank against a tank of gas
Champion rates the 201319 at 14 hours on its 2.25 gal tank of gasoline and 21 hours on a 20 lb propane cylinder, both at a quarter load. Westinghouse gives the WGen3600DFv 14 hours on its 4 gal tank and 16.5 hours on a 20 lb cylinder, without saying at what load. At light loads, then, one standard grill cylinder runs a mid-size generator for most of a day, and you can keep several on hand.
Energy per gallon
A gallon of propane holds 91,452 Btu, against 120,214 for gasoline, per the EIA: about 24% less energy. So a gallon of propane runs a generator for less time than a gallon of gas. At the EIA's US averages, gasoline costs $4.28 a gallon (week of Oct 19, 2026, taxes included) and residential propane $2.69 (taxes excluded). Per million Btu that's about $35.64 for gasoline and $29.40 for propane.
The EIA propane price is for propane delivered in bulk to homes, so it isn't what you'd pay to fill or swap a 20 lb cylinder. Check your local cylinder price before you count on propane being cheaper. For a sense of scale on gasoline, the Champion 201319 at a quarter load burns about 69¢ of gas an hour at the national average.
How each fuel keeps between outages
A backup generator can sit for months between outages, and that's where gasoline is weak. Champion's manual for the 201319 says gasoline keeps for up to a year in the tank only with a properly formulated stabilizer, in a cool, dry place, and that gas left in the carburetor may gum it up within two to four weeks. Its storage steps for gasoline don't apply to propane, which the manual says won't leave build-up or clog the carburetor.
Propane has its own rules. Champion's manual says to keep the cylinder upright with the valve on top, on level ground away from heat and out of the exhaust stream, to check the cylinder's requalification date, and to disconnect it and close the valve for storage. After storage, test the fittings for leaks with soapy water before you start the generator.
Very cold weather can slow propane down. Champion notes that frost on the cylinder and regulator is normal, but a very cold cylinder vaporizes propane more slowly and may not keep up with the engine. Its fix is to swap in a second cylinder while the first warms up, or to set the cylinder where the engine's cooling air flows out, never in the exhaust path.
Which one to buy
Choose dual fuel if
- The generator will sit unused for months between outages, and you'd rather keep a sealed cylinder than rotate stabilized gasoline.
- Gas stations near you tend to close or run dry after storms. A second fuel gives you a fallback.
- You already keep propane cylinders for a grill.
Gasoline only is fine if
- You need every watt the generator can make. Propane costs about a tenth of the running watts.
- You use the generator often enough to burn through fresh gas, and you have somewhere safe to store it.
Natural gas is a third option on standby generators, which run on gas or propane straight from the utility line or a tank; the whole home generator cost page covers what that takes. For portable models, see our inverter generator picks, several of which are dual fuel, and the inverter vs conventional comparison.