| Quick Facts | |
|---|---|
| Propane lower heating value | 84,250 Btu per gallon (DOE Alternative Fuels Data Center) |
| Gasoline lower heating value | 112,114-116,090 Btu per gallon (DOE Alternative Fuels Data Center) |
| Natural gas average heat content | about 1,037 Btu per cubic foot, 2025 average (EIA) |
| CPSC minimum generator distance from home | at least 20 feet, exhaust pointed away from doors and windows |
| Portable-generator CO deaths since 2009 | est. 765 deaths, about 40% of all consumer-product CO deaths (CPSC) |
| Westinghouse 14500 tri-fuel output by fuel | 14,500W/11,500W gasoline; 13,500W/10,500W propane; 12,000W/9,500W natural gas (feed: tri-fuel-generator/best) |
| DuroStar DS13000MXT engine | 500cc tri-fuel engine with CO Alert automatic shutdown (feed: tri-fuel-generator/best) |
| ERAYAK 4500W dual-fuel output | 4,500W peak gasoline vs 4,050W peak propane (feed: tri-fuel-generator/best) |
What is a tri-fuel generator?
A tri-fuel generator is a single engine built to burn gasoline, liquid propane, or natural gas, switched with a selector valve rather than three separate machines.
Shopping for a specific model? See our best rv generator picks — 10 models compared on the specs that decide it.
Tri-fuel describes the fuel system, not the size of the generator. The engine itself is a standard small gasoline engine; what makes it tri-fuel is a carburetor and fuel line modified to also accept propane and natural gas, plus a dial or switch on the control panel that tells the carburetor which one is coming in. DuroStar's DS13000MXT lists exactly that setup: a 500cc engine that runs on gasoline, propane, or natural gas, controlled from a front panel with a push-button start and a fuel selector. The Generac 12,500 Starting Watt Tri-Fuel Portable Generator uses the same idea, describing itself as switching between gasoline, liquid propane, or natural gas through what it calls a simple fuel selector.
Westinghouse's 14,500-peak-watt Tri-Fuel Home Backup Portable prints a separate rating for each fuel: 14,500 peak watts and 11,500 running watts on gasoline, 13,500 peak and 10,500 running on propane, and 12,000 peak and 9,500 running on natural gas, all from the same 550cc engine. Three fuels, three wattage columns, one physical unit. Anyone shopping our tri-fuel generator picks should read the propane and natural gas numbers on the spec sheet, not just the gasoline figure printed largest on the box.
How the fuel switch actually works
Switching fuels means routing a different supply, gasoline from the built-in tank, propane from an external cylinder, or natural gas from a home line, into the same carburetor, with a selector or hose swap deciding which one the engine burns.
On a tri-fuel unit, gasoline still comes from the onboard tank the way it would on any portable generator. Propane runs off an external cylinder through a hose and regulator, and natural gas runs off a low-pressure line, typically a household hookup, through a separate hose kit. The DuroMax XP13000HXT handles the choice with what DuroMax calls a front-facing interface for changing fuel type, alongside a push-button start and a remote-start option. That's a meaningfully different setup from a generator that only takes one fuel: no interface to learn, no hose kit stored in the garage, no extra step before starting it up.
The tradeoff is weight and complexity. A single-fuel machine like the LIFAN 2300W Gasoline Inverter Generator has one fuel path, a 1.32-gallon tank, and nothing to switch, which is part of why it stays at 42.8 lb against the 230 lb of the Westinghouse tri-fuel units. Buyers who only ever plan to run gasoline and want the lighter, simpler machine are better served browsing our gas generator guide than paying for propane and natural gas capability they won't use.
Why wattage drops on propane and natural gas
Propane and natural gas pack less usable energy per unit than gasoline, so the same engine pulls in less fuel energy per intake stroke and makes less power, which is why manufacturers print a separate wattage rating per fuel.
The gap comes down to energy density, not the quality of the generator. The U.S. Department of Energy's Alternative Fuels Data Center lists propane's lower heating value at 84,250 Btu per gallon, against roughly 112,114 to 116,090 Btu per gallon for gasoline. Natural gas is measured by volume rather than by the gallon, and the U.S. Energy Information Administration puts the average heat content of natural gas delivered to consumers at about 1,037 Btu per cubic foot, a figure that varies slightly by region and utility. Feed a carburetor less energy per stroke and the engine makes less mechanical power, which is exactly the pattern in Westinghouse's published numbers: 14,500 watts peak on gasoline, stepping down to 13,500 on propane and 12,000 on natural gas from the same engine block.
That 2,500-watt spread between the gasoline and natural gas ratings on one unit is large enough to strand a rooftop RV air conditioner with a hard startup surge. Sizing a tri-fuel generator off the gasoline number, then running it on natural gas at a full hookup site, is a common way to end up short of the wattage a compressor needs to start.
Running a tri-fuel generator on natural gas at a full hookup
Natural gas suits a tri-fuel generator parked at a site with a gas line, since it removes the need to store or haul propane cylinders or gas cans, but it also delivers the lowest wattage of the three fuel options.
RVers who spend most nights at developed campgrounds or a home pad with a gas line get a real convenience from the natural gas option: no fuel to buy, store, or spill, and no cylinder to swap mid-trip. Generac's 12,500 Starting Watt Tri-Fuel model markets that flexibility alongside a 7.5-gallon steel tank on the gasoline side, roughly 9.5 hours of runtime at 50% load, and CO sensor protection it calls COsense. The DS13000MXT pairs its tri-fuel switching with the same pitch, framed as whole-home backup capacity that happens to travel.
The catch is the derate covered above. A generator that reads 13,000 watts on the box is not delivering 13,000 watts on natural gas, and boondockers without a gas hookup don't get the option at all, since natural gas isn't something carried in a tank the way propane or gasoline is. For a straight comparison of how these tri-fuel-capable models stack up against natural-gas-focused competitors on spec and price, our natural gas generator guide lines up ten of them side by side.
Carbon monoxide risk is the same no matter which fuel is burning
All three fuels in a tri-fuel generator produce carbon monoxide when burned, so the placement rules, at least 20 feet from the home or RV with exhaust pointed away from doors and windows, apply regardless of which fuel is selected.
Switching from gasoline to propane or natural gas doesn't change the exhaust chemistry in any way that matters for safety. All three are combustion fuels, and all three produce carbon monoxide as a byproduct, an invisible, odorless gas that's just as dangerous coming out of a natural-gas-fired tri-fuel unit as a straight gasoline model. The U.S. Consumer Product Safety Commission recommends operating any portable generator outdoors only, at least 20 feet from the home, camper, or RV, with exhaust directed away from windows, doors, and vents, and it specifically warns that a porch, carport, or open garage door isn't far enough.
The numbers behind that warning are blunt. CPSC's non-fire carbon monoxide death data attributes an estimated 765 non-fire CO poisoning deaths to portable generators since 2009, about 40% of all consumer-product CO deaths the agency tracks. A CO sensor like the one built into the DS13000MXT or Generac's COsense system adds a real backstop, shutting the unit down automatically if CO builds up nearby, but it's a second layer of protection, not a substitute for keeping the generator far enough from any door or window in the first place.
Tri-fuel vs dual-fuel vs single-fuel: which one is worth buying
Buy tri-fuel only if at least two of the three fuel options will actually get used; otherwise a single-fuel or dual-fuel unit is lighter, simpler, and usually cheaper for the same wattage.
Tri-fuel capability is a real feature, not a gimmick, but it's only worth the added weight and price if the fuel flexibility gets used. Dual-fuel units like the ERAYAK 4500W Dual-Fuel Portable Inverter Generator and the PowerSmart 3800 Watt Dual Fuel Inverter Generator cover gasoline and propane, the pairing most RVers and campers actually reach for, without the extra natural gas hardware most people never hook up. ERAYAK rates its unit at 4,500W peak on gasoline and 4,050W peak on propane with auto-switching when the gas tank runs low, a smaller version of the same derate pattern that shows up on the bigger tri-fuel machines.
Buyers who know they'll only ever run gasoline, tailgating, weekend camping, a garage backup, get more generator per pound and per dollar from a single-fuel inverter. The Oxseryn 4400-Watts Inverter Generator, gasoline-only with a 30A RV-ready outlet, delivers 4,400 peak watts and 3,400 running watts at 57 lb, about a quarter of the weight of the Westinghouse tri-fuel units for a comparable running-watt figure. The honest way to shop this category is to start from how the generator will actually get fueled on a normal trip, then match the fuel system to that answer instead of buying the widest fuel compatibility on the shelf.