What the third fuel actually is
A dual fuel generator runs on gasoline or propane. A tri fuel generator adds natural gas — the same supply that feeds a furnace or a range in a house with a gas meter.
That is the entire difference. Tri fuel machines are not more powerful, quieter or more reliable than their dual fuel equivalents. They have one extra inlet and a regulator, and they cost more.
The one question that decides it
Does your house have a natural gas line, and are you prepared to pay to plumb an outdoor connection point?
If the answer is no — no gas service, a propane-only rural property, or an unwillingness to add a gas outlet — then tri fuel is money spent on a fuel you cannot use. If the answer is yes, the third fuel changes what a long outage feels like.
How the three fuels compare
| Fuel | Output | Storage | Runs out? |
|---|
| Gasoline | Highest of the three | Degrades in months; needs stabilizer and rotation | Yes — and stations need power to pump |
|---|
| Propane | Lower than gasoline on the same machine | Indefinite in a sealed cylinder | Yes, but you can store a lot of it safely |
|---|
| Natural gas | Lowest of the three | None — it arrives by pipe | No, unless the utility loses supply |
|---|
Output varies by machine and each manufacturer publishes its own figures per fuel — the DuroMax tri fuel unit above states all three. Never assume the headline gasoline number applies on gas or propane.
Note the pattern: the more convenient the fuel, the less power you get from it. A generator that makes 13,000W on gasoline makes meaningfully less on natural gas, so a tri fuel machine has to be sized against its natural gas rating if that is how you plan to run it.
What tri fuel costs you beyond the sticker
- A gas outlet. An outdoor quick-connect plumbed from the house supply, fitted by a licensed plumber in most jurisdictions.
- Derated output. Size the machine on the natural gas figure, not the gasoline one, or the whole plan fails on the first cold night.
- A dependency on the utility. Gas supply usually survives storms that take out power, but not always — earthquakes and major infrastructure damage can take both.
What dual fuel gets right
Propane is the underrated fuel in this comparison. It stores indefinitely, which is exactly what a machine used twice a year needs; it burns cleaner through a carburetor, so the machine is less likely to refuse to start after a year in the garage; and a few 20 lb cylinders in a shed is a genuinely practical store — the propane roundup covers the trade in full.
Gasoline remains the fuel for maximum output, and the sensible pattern is to run propane by default and keep gasoline for the moments you need the machine at full capacity.
Who should buy which
- Buy tri fuel if you have natural gas service, expect multi-day outages, and will pay for the gas outlet.
- Buy dual fuel if you have no gas line, if outages are hours rather than days, or if you want the money to go into a transfer switch instead.
- Consider neither if a battery covers your outage history — the generator versus power station page frames that decision.
The short version
- Tri fuel = dual fuel + natural gas. Nothing else changes.
- No gas line, no reason. The capability is unusable without one.
- Natural gas gives the lowest output of the three fuels — size against that rating.
- Propane is the quiet winner for storage, which is why dual fuel suits most households.
