Generator fuel consumption
At half load, a 22 kW standby generator uses natural gas at about 204 cubic feet each hour, or propane at 2.53 gallons an hour. Each size listed here comes from the manufacturer's fuel table.
Hourly fuel use by generator size
Generac lists fuel data for each model. At 18 kW and 24 kW, and again at 26 kW and 38 kW, the rated hourly burn is no more than that of the next size down, so per hour use doesn't climb in step with kW.
| Generator | Natural gas, half load | Natural gas, full load | Propane, half load | Propane, full load | Fuel table |
|---|---|---|---|---|---|
| 10 kW | 101 ft³ | 127 ft³ | 0.97 gal | 1.48 gal | Generac Guardian 10 kW |
| 14 kW | 195 ft³ | 256 ft³ | 1.81 gal | 3.07 gal | Generac Guardian 14 kW |
| 18 kW | 169 ft³ | 247 ft³ | 1.70 gal | 3.02 gal | Generac Guardian 18 kW |
| 22 kW | 204 ft³ | 327 ft³ | 2.53 gal | 3.90 gal | Generac Guardian 22 kW |
| 24 kW | 203 ft³ | 306 ft³ | 2.53 gal | 3.90 gal | Generac Guardian 24 kW |
| 26 kW | 188 ft³ | 333 ft³ | 2.06 gal | 3.63 gal | Generac Guardian 26 kW |
| 32 kW | 258 ft³ | 417 ft³ | 3.40 gal | 5.00 gal | Generac XG03245 |
| 38 kW | 255 ft³ | 437 ft³ | 2.90 gal | 5.20 gal | Generac RG03824 |
| 48 kW | 336 ft³ | 607 ft³ | 4.20 gal | 6.60 gal | Generac RG04845 |
The hourly cubic feet and gallons for each model are taken from Generac's published fuel table.
Propane tank run time by size
| Generator | 250 gal, half load | 250 gal, full load | 500 gal, half load | 500 gal, full load |
|---|---|---|---|---|
| 10 kW | 206 h | 135 h | 412 h | 270 h |
| 14 kW | 110 h | 65 h | 221 h | 130 h |
| 18 kW | 118 h | 66 h | 235 h | 132 h |
| 22 kW | 79 h | 51 h | 158 h | 103 h |
| 24 kW | 79 h | 51 h | 158 h | 103 h |
| 26 kW | 97 h | 55 h | 194 h | 110 h |
| 32 kW | 59 h | 40 h | 118 h | 80 h |
| 38 kW | 69 h | 38 h | 138 h | 77 h |
| 48 kW | 48 h | 30 h | 95 h | 61 h |
A tank filled to 80% gives you the usable share. The propane tank for a generator page covers 120 and 1,000 gallon tanks.
What you pay per hour
| Generator | Natural gas, half load | Natural gas, full load | Propane, half load | Propane, full load |
|---|---|---|---|---|
| 10 kW | $2.21 | $2.78 | $2.65 | $4.04 |
| 14 kW | $4.27 | $5.61 | $4.94 | $8.38 |
| 18 kW | $3.70 | $5.41 | $4.64 | $8.24 |
| 22 kW | $4.47 | $7.17 | $6.91 | $10.65 |
| 24 kW | $4.45 | $6.71 | $6.91 | $10.65 |
| 26 kW | $4.12 | $7.30 | $5.62 | $9.91 |
| 32 kW | $5.66 | $9.14 | $9.28 | $13.65 |
| 38 kW | $5.59 | $9.58 | $7.92 | $14.20 |
| 48 kW | $7.37 | $13.31 | $11.47 | $18.02 |
The EIA puts the US average residential natural gas price at $21.92 for a thousand cubic feet (March to August 2026); propane runs $2.73 a gallon (October 26, 2026). Every state's page uses that state's own prices.
Portables that run on gasoline
| Portable | Gasoline, half load | Gasoline, full load | Cost an hour, half load |
|---|---|---|---|
| 3,000 W | 0.31 gal | 0.52 gal | $1.33 |
| 3,500 W | 0.35 gal | 0.58 gal | $1.48 |
| 4,000 W | 0.38 gal | 0.65 gal | $1.62 |
| 5,000 W | 0.45 gal | 0.79 gal | $1.91 |
| 6,500 W | 0.55 gal | 0.99 gal | $2.34 |
| 7,500 W | 0.62 gal | 1.12 gal | $2.63 |
| 8,000 W | 0.65 gal | 1.19 gal | $2.77 |
| 10,000 W | 0.79 gal | 1.46 gal | $3.35 |
| 12,000 W | 0.92 gal | 1.73 gal | $3.93 |
| 13,000 W | 0.99 gal | 1.87 gal | $4.22 |
| 15,000 W | 1.12 gal | 2.14 gal | $4.79 |
For October 26, 2026, the EIA US regular average puts gasoline at $4.27 a gallon. Gasoline spoils in two to three months if you don't add a stabilizer. For outages, a portable needs either stored fresh fuel or a propane cylinder.
Fuel use questions
How much propane does a generator use?
A 22 kW home standby generator burns propane at about 2.53 gallons an hour when it's at half load, and 3.90 gallons an hour at full load. A 10 kW unit uses 0.97 gallons when it runs at half load.
How much natural gas do whole house generators use?
A 22 kW unit takes in about 204 cubic feet each hour at half load and 327 cubic feet each hour at full load, so your meter has to handle that on top of what the furnace and water heater draw.
Is a dual fuel generator worth it?
A dual fuel portable can run on gasoline, or you can run it with a propane cylinder. Propane keeps for years, and after storage the engine starts up cleaner when it runs on propane. That same engine makes about 10% more power on gasoline. With home standby units, you pick natural gas or propane when the unit is installed.