Most whole-house standby generators run on either natural gas or propane, and many dual-fuel models support both — but the two fuels aren't interchangeable in practice, and the right one depends more on what's already available at your house than on the generator itself.
The core tradeoffs
| Natural gas | Propane | |
|---|---|---|
| Supply | Continuous via utility pipeline — never runs out | Finite — limited to tank size, needs refilling |
| Output | Slightly lower than propane for the same generator | Slightly higher output than natural gas |
| Requires | An existing natural gas line to the home | A propane tank (owned or leased) on the property |
| Cost per running hour | Generally cheaper where available | Generally more expensive per hour |
| Availability | Only where utility gas service exists | Works anywhere — no utility dependency |
Why natural gas is the default when it's available
A generator plumbed into an existing natural gas line never runs out of fuel during an outage — no tank to monitor, no delivery truck to schedule during a regional emergency when everyone else is also trying to refuel. For homes that already have gas service, this makes natural gas the practical default for a standby install.
Why propane is the right call for many homes
If natural gas service isn't available at your address — common in rural areas — propane is usually the only whole-house standby option, since running a new gas line can be far more expensive than installing a propane tank. Propane also slightly outperforms natural gas in output for the same generator model, and a large enough tank (500 gallon or bigger) can cover many days of runtime.
Dual-fuel and tri-fuel: hedging your bet
Many portable and mid-size generators—see our generator picks for current dual-fuel and tri-fuel models—let you switch between gasoline, propane, and sometimes natural gas. This isn't about picking the "better" fuel permanently; it's insurance against one fuel source being unavailable when you actually need the generator, which matters most during a regional event when gas stations and propane suppliers may be tapped out.