Dual fuel generators: two fuels, one backup plan
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Quick answer
A dual fuel generator runs on gasoline or propane, so you can use whichever fuel you can get. Expect about 10% less power on propane. Champion's 7,500 watt dual fuel model drops to 6,750 running watts on propane, and its 8,500 watt model to 7,650. Propane keeps in storage, but tanks go fast: Champion rates its 7,500 watt unit at 5.5 hours on a 20 pound tank at half load, versus 10 hours on its 7.7 gallon gas tank. Run it outdoors, at least 20 feet from the house.
Why two fuels help in an emergency
Gas stations close or run dry during big storms, and gasoline goes stale in storage. Champion says propane is a clean-burning fuel with a longer shelf life. A dual fuel generator lets you keep sealed propane tanks as your long-term reserve, and use gasoline when it is easy to buy. Champion's dual fuel models use a fuel selector switch for switching between sources safely.
How much power you give up on propane
Champion says propane typically delivers about 10% less wattage than gasoline. Its spec sheets bear that out:
| Model | Gasoline (start / run) | Propane (start / run) |
|---|---|---|
| Champion 7500W dual fuel (201281) | 9,375 / 7,500 W | 8,400 / 6,750 W |
| Champion 8500W dual fuel (201493) | 10,000 / 8,500 W | 9,000 / 7,650 W |
Both drop exactly 10% in running watts. So size your generator from the propane number if propane is your backup fuel. Add your running watts, add the largest starting load, and compare to the propane rating. Our generator for your house guide walks through the math.
Run time: tanks go faster than you think
Champion rates its 7,500 watt dual fuel unit at 10 hours at 50% load on a full 7.7 gallon gas tank, and 5.5 hours at 50% load on a 20 pound propane tank. Its 8,500 watt model is rated 10 hours on gas and 5 hours on propane at half load.
Do the math for a long outage. Running 24 hours a day at half load on the 7,500 watt unit would use about four and a half 20 pound tanks a day (24 divided by 5.5). Running the generator in blocks, long enough to cool the fridge and run the sump pump and then shutting it off, stretches propane much further. If you want days of propane run time, plan on several tanks or a larger tank set up by a propane professional.
Features to compare
- Outlets. Champion's 7,500 watt dual fuel unit has a 120/240V L14-30R locking outlet, a 120V L5-30R, and two 120V 20A GFCI duplex outlets. The 8,500 watt adds a 14-50R. Have an electrician match any transfer switch to the outlet you will use.
- Electric start. Both include the battery.
- CO shut-off. Both have Champion's CO Shield, which shuts the engine off if CO builds up.
- Weight and noise. Both are about 205 pounds and rated 74 dBA at 23 feet.
- Warranty. Both carry a 3 year limited warranty.
Storing fuel safely
NFPA's generator safety sheet says to store generator fuel in a container intended for the purpose and correctly labeled, outside living areas. Turn the generator off and let it cool before refueling. Westinghouse's dual and tri fuel manual adds: keep the propane cylinder away from the generator exhaust, set the generator and cylinder on a flat surface, and do not start the unit if you smell propane. Check hose connections with soapy water, never a flame.
Run it in the right place
The fuel choice does not change the carbon monoxide risk. The U.S. Consumer Product Safety Commission says to run portable generators outside only, at least 20 feet from the house. Never run one inside a home, garage, basement, crawlspace or shed, even with the doors open. Point the exhaust away from doors, windows and vents.
What to look for when you buy
7,500 watt dual fuel generator with CO shut-off (example: Champion 201281)
Best for: A typical home's fridge, sump pump, furnace fan and lights, on gas or propane
Champion lists 7,500 running watts on gasoline and 6,750 on propane, 10 hours on gas or 5.5 hours on a 20 pound tank at half load, an L14-30R outlet and CO Shield.
Watch out: It weighs 205 pounds and is rated 74 dBA at 23 feet.
See options on Amazon (opens Amazon in a new tab)8,500 watt dual fuel generator with CO shut-off (example: Champion 201493)
Best for: Homes that need more headroom on propane
Champion lists 8,500 running watts on gas and 7,650 on propane, plus L14-30R and 14-50R outlets and CO Shield.
Watch out: Propane run time is 5 hours per 20 pound tank at half load.
See options on Amazon (opens Amazon in a new tab)Extra 20 pound propane tanks
Best for: Building a propane reserve that does not go stale
At about 5 to 5.5 hours per 20 pound tank at half load, a few full tanks cover several days of run-in-blocks use.
Watch out: Store cylinders outdoors, never in the house or garage, and keep them away from the generator's exhaust.
See options on Amazon (opens Amazon in a new tab)Propane tank fuel gauge
Best for: Knowing how much run time is left before a tank runs out
Run time per tank is short, so a gauge helps you swap tanks before the generator stalls with a load on it.
Watch out: Check that it fits your tank's valve type.
See options on Amazon (opens Amazon in a new tab)Questions people ask
- Do dual fuel generators lose power on propane?
- Yes, about 10%. Champion's 7,500 watt dual fuel model runs 6,750 watts on propane, and its 8,500 watt model runs 7,650.
- How long does a 20 lb propane tank last on a generator?
- Champion rates its 7,500 watt dual fuel unit at 5.5 hours at half load on a 20 pound tank, and its 8,500 watt unit at 5 hours.
- Is propane or gas better for storing?
- Champion says propane has a longer shelf life and burns cleaner. Gasoline needs stabilizer and rotation.
- Can I switch fuels while the generator runs?
- Follow your manual. Champion's dual fuel models use a fuel selector switch designed for switching between sources safely.
Sources
- 7500W Electric Start Dual Fuel Generator with CO Shield (201281), Champion Power Equipment
- 8500W Electric Start Dual Fuel Generator (201493), Champion Power Equipment
- What Size Generator Do I Need?, Champion Power Equipment
- Generator Safety tip sheet, National Fire Protection Association
- As Winter Storms Threaten Millions in the U.S., CPSC Issues Safety Tips, U.S. Consumer Product Safety Commission
- iGen8200TFc Owner's Manual, Westinghouse Outdoor Power Equipment