How much power does each fuel give?
Air-cooled standby generators make roughly 8 to 14 percent less power on natural gas than on propane. The rated figures below come from the manufacturers' spec sheets.
| Generator | Propane | Natural gas |
|---|---|---|
| Generac Guardian 22 kW | 22 kW | 19.5 kW |
| Generac Guardian 24 kW | 24 kW | 21 kW |
| Generac Guardian 26 kW | 26 kW | 22.5 kW |
| KOHLER 20RCA | 20 kW | 18 kW |
| KOHLER 26RCA | 26 kW | 24 kW |
| KOHLER 38RCLC (liquid-cooled) | 38 kW | 38 kW |
On natural gas we size to the lower number. See what size generator a house needs.
How much fuel does a generator burn?
Generac lists its 24 kW Guardian at 203 cubic feet of natural gas an hour at half load and 306 at full load. On propane it is 2.53 gallons an hour at half load and 3.90 at full load. Most of the time a house runs well below full load, so half load is the more useful figure.
With propane, that means a long outage uses a real share of the tank. A generator also burns a small amount every time it runs its weekly or biweekly exercise. Generac's Fuel Monitor can show the propane tank level in the Mobile Link app.
What does natural gas involve?
The generator connects to the house's gas service, and a licensed gas fitter runs a pipe sized for the generator at full load. The longer the run, the larger the pipe. The question to settle early is the meter. A meter sized for a furnace and a range may not supply a generator as well, and the gas company decides. In Massachusetts, National Grid asks for a meter upgrade and added-load request when you add gas equipment, and there can be a cost.
What does propane involve?
You need a propane tank, a supplier to fill it, and a licensed gas fitter to connect it. The local fire department permits the tank and inspects it before it can be filled. Tanks have to sit set distances from the house, property lines and anything that could ignite, and the fire department checks the drawings. If the house already has propane for heat or cooking, the generator can often share the tank, as long as it is big enough.
You contract the tank and deliveries with your propane supplier. We coordinate the location, the permit and the connection.
