Natural Gas or Propane: Which Fuel Suits Your Generator?
For most properties the answer is decided by what is already available at the address rather than by preference. Here is what actually differs between the two, and what has to be checked before either is chosen.
The Practical Differences
Generac standby generators run on natural gas or liquid propane. The generator itself is largely the same machine; what changes is where the fuel comes from and what that means during a long outage.
Natural gas
- Piped in continuously. There is no tank to fill and no delivery to arrange.
- Runtime is limited by the supply, not by storage. As long as the utility gas is flowing, the generator can keep running.
- No fuel to check before storm season. One fewer thing to forget.
- Requires a gas main at the property and a meter and service able to carry the extra load.
The catch: the gas supply has to be adequate. A standby generator is a significant additional load and the meter or line sometimes needs upgrading.
Propane (LP)
- Works anywhere. No gas main needed, which is why it is common outside town.
- Runtime is limited by the tank. Capacity, generator model and load together decide how long you have.
- Stores well. Propane does not degrade the way gasoline does.
- Needs a tank on the property, sized for the generator and positioned to code.
The catch: fuel level matters. Deliveries slow down once weather is in the forecast, so the level is worth checking before storm season rather than during it.
How Long Will It Run?
On natural gas, for as long as the supply holds. That is genuinely the answer, and it is the main reason people choose it where it is available.
On propane, it depends on three things together, and no one of them settles it:
- Tank capacity. The obvious one, and the only one most people think about.
- The generator model. A larger unit burns more fuel to produce more power.
- How hard it is working. This is the one that surprises people. A generator carrying an entire all-electric house through a January cold snap consumes at a completely different rate from the same unit carrying essential circuits on a mild afternoon. The load is not fixed, so neither is the runtime.
We do not publish a burn rate, and you should be wary of anyone who quotes you one without knowing your model and your load. A figure taken from a general chart is exactly how a household ends up sizing a tank too small and running out on day three of an outage.
What Gen-Man does instead is work through tank sizing with you during planning, based on your unit, your coverage and how long you want to be able to run without a delivery.
What Gets Checked on the Fuel Side
- Whether natural gas is available at all, and where the line runs.
- Whether the existing meter and service can carry the generator alongside the furnace, water heater, range and anything else already on gas.
- Gas pressure and volume. A generator starved of fuel will run its brief weekly exercise happily and then struggle under real load, which is a miserable way to discover a problem.
- Where a propane tank can legally and practically go, if one is needed, and what size the site calls for.
- The routing of the fuel line from the supply to the generator pad.
Gen-Man runs the gas or propane line as part of the installation and coordinates with a propane supplier where a tank needs installing. Gas piping and regulators are not homeowner work — that is a licensed trade for good reason.
Where Diesel Fits
There are diesel models in our catalog, including extended tank versions, and they have a real place: sites with no gas main where propane is impractical, and applications that specifically call for diesel.
The trade is fuel management. A diesel unit carries its own tank, which means deliveries to arrange, fuel to keep fresh, and storage to think about — none of which a gaseous unit asks of you. For commercial sites the website makes the same point: Generac's gaseous commercial units avoid diesel storage entirely, which is usually why businesses pick them.
Generator Fuel FAQ
We Check the Fuel Side Before Anything Is Quoted
Gas availability, meter capacity, line routing and tank sizing are all part of the free site evaluation.