Last updated: September 28, 2026
Quick Answer
For home backup, a dual fuel generator is usually the better buy, because it runs on gasoline or propane. On propane it makes about 5 to 10 percent less power, but propane stores for years without going stale [5]. A gas-only model costs a little less and fits buyers who only need occasional power.
Who this guide is for:
- Homeowners planning backup power for storms and outages
- Buyers in hurricane and ice storm areas, where gas stations can close for days
- Campers and RV owners who already carry propane
What Is a Dual Fuel Generator?
A dual-fuel generator is a portable generator whose engine can burn two fuel types: gasoline and propane. You pick the fuel with a selector switch or valve. Many models let you switch fuels without shutting the engine off.
Two fuel options beat one fuel source when the grid goes down. If one fuel runs short, the other keeps you on reliable power.
A traditional generator runs on gasoline only. A tri fuel generator adds natural gas as a third choice.
Both types use the same kind of engine, so they feel the same to own. The difference is the fuel system. A dual fuel unit adds a propane inlet, plus a hose and regulator that fit a standard 20 lb tank.
Are Dual Fuel Generators Better Than Gas-Only Models?
For most home backup buyers, yes. A dual fuel generator gives you a second fuel and a way to store fuel for years, for a small price premium. Here are the pros and cons side by side. A gas-only model still makes sense if you use it a few times a year and have easy access to fresh gas.
| Factor | Dual Fuel | Gas Only |
|---|---|---|
| Fuels | Gasoline or propane | Gasoline |
| Power on propane | About 5 to 10% lower than on gas | Not available |
| Fuel storage | Propane keeps for years | Gas breaks down in months |
| Refueling in an outage | Swap a propane tank or add gas | Needs fresh gas |
| Price | A little higher | Lower |
| Routine maintenance | Same engine care, plus a hose check | Engine care only |
Picture a three-day ice storm. The gas station down the road has no power to run its pumps. With a dual fuel unit, you connect the grill tank and keep the fridge cold.
How Much Power Do You Lose on Propane?
A dual fuel generator's power output drops about 5 to 10 percent on propane compared with gasoline. The HB5040DC is rated 3,300 running watts on gasoline and 3,100 on propane, a drop of about 6 percent [5].
The reason is chemistry. Each gallon of propane holds about 91,500 BTU, while a gallon of gasoline holds about 120,200 BTU [1]. Less energy reaches the engine in each cycle, so it makes a little less power.
Here is the practical rule: if you plan to run on propane, size your generator on its propane rating. Our generator sizing calculator helps you add up your loads.
3800W/3500W Gas/Propane Dual Fuel Inverter Generator w/ CO Alert HB5040DC
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Shop NowWhich Costs Less to Run: Gasoline or Propane?
It depends on local prices, because propane holds about 24 percent less energy per gallon than gasoline [1]. A generator burns more propane by volume to make the same power. So propane has to cost roughly a quarter less per gallon to match gasoline.
A dual fuel generator lets you run whichever type of fuel is cheaper that week. That matters most in a long outage, when gas prices often jump.
Load matters too. Gasoline feeds from the built-in fuel tank, and propane feeds from an external tank. On either fuel, lighter loads and ECO mode improve fuel efficiency.
Planning a multi-day outage on propane? Our guide to how long a propane generator can run shows runtime by tank size.
Do Dual Fuel Generators Need More Maintenance?
Only a little. Routine care is the same for both types. Change the oil, clean the air filter, and replace the spark plug as your manual directs.
A dual fuel unit adds one job. Check the propane hose and regulator for cracks and leaks before each season.
Propane can even make upkeep easier. It does not leave gummy deposits the way stale gasoline can. Before storage, run the carburetor dry or add stabilizer, as your manual directs.
Is Propane Better for the Environment?
Propane burns cleaner than gasoline. It releases about 11 percent less carbon dioxide for the same amount of energy, based on U.S. EIA emission factors [2]. It also comes in a sealed tank, so there are no spills or fumes from a gas can.
Cleaner does not mean safe indoors. Every fuel-burning generator makes carbon monoxide, which you cannot see or smell [3].
Safety first: Never run any generator indoors or in a garage, even with doors and windows open. Run it outside, at least 20 feet from the house, with the exhaust pointed away [3]. Put a battery CO alarm on every floor.
Which Fuel Is Better for Emergency Storage?
Propane is the better storage fuel. It sits as a liquid in a sealed, pressurized tank [4], so it does not go stale. Untreated gasoline starts to break down within a few months.
Store propane tanks outdoors, upright, and away from the house. Store gasoline in approved cans, add stabilizer, and use it up on a rotation.
After a natural disaster, fuel deliveries can stop for days. With a dual fuel generator, you can keep multiple fuel sources on hand. Gasoline covers the first day, and a few propane tanks carry you through a longer outage. See our power outage supply checklist for the rest of your kit.
The Bottom Line
A dual fuel generator is the safer bet for home backup and the more reliable power source in a long outage. You get two fuels, fuel that stores for years, and only a small power loss on propane. A gas-only model is fine if you use it now and then and can always buy fresh gas.
Your Next Steps
- Add up your loads with the generator sizing calculator.
- Size on the propane rating if you plan to run propane.
- Compare models in our dual fuel generator collection or the full portable generator lineup.
- Read our buying guide on how to choose a dual fuel portable generator.
- Stock fuel early: fill two propane tanks and a stabilized gas can before storm season.
Frequently Asked Questions
Quick answers to the questions buyers ask most about dual fuel generators.
What is a dual fuel generator?
A dual fuel generator is a portable generator that runs on gasoline or propane. You choose the fuel with a selector switch or valve. Many models let you switch fuels while the engine runs.
Can you switch fuels while the generator is running?
On many dual fuel models, yes. The selector moves the engine from one fuel to the other without a restart. Check your owner's manual, because the steps vary by model.
Do dual fuel generators make less power on propane?
Yes, usually about 5 to 10 percent less. The HB5040DC, for example, is rated 3,300 running watts on gasoline and 3,100 on propane. Size your generator on its propane rating if you plan to run propane.
Which fuel stores longer, gasoline or propane?
Propane. It stays sealed in a pressurized tank and does not go stale. Untreated gasoline starts to break down within a few months, so it needs stabilizer and regular rotation.
Are dual fuel generators louder than gas-only generators?
No. Noise depends on the engine, muffler, and enclosure, not on the fuel. Compare the dB rating on the spec sheet, measured at the same distance.
Can I use a dual fuel generator indoors if I open a window?
No. Never run any fuel-burning generator indoors or in a garage, even with doors and windows open. Run it outside, at least 20 feet from the house, with the exhaust pointed away.
Can I convert my gas-only generator to dual fuel?
Conversion kits exist, but they can void your warranty and affect emissions certification. For most buyers, a factory dual fuel model is the safer choice.
Do I need a permit for a dual fuel generator?
Portable generators usually need no permit. Rules change if you install a permanent propane tank or wire the generator into your panel. Check with your local building department before you do either.
References
- U.S. Energy Information Administration. "British thermal units (Btu)." eia.gov
- U.S. Energy Information Administration. "Carbon Dioxide Emissions Coefficients." eia.gov
- U.S. Consumer Product Safety Commission. "What to Know About Generators and Carbon Monoxide." cpsc.gov
- U.S. Department of Energy, Alternative Fuels Data Center. "Propane Fuel Basics." afdc.energy.gov
- PowerSmart. "HB5040DC 3800W Inverter Generator Instruction Manual," technical data. Manual (PDF)
