The short answer
A 7,500 W portable generator running 3,000 W of appliances burns about 0.59 gallons of gasoline an hour, about $2.37 at the U.S. average of $4.00 a gallon (EIA, week of 2026-11-09), or $71.12 for a 3-day outage at 10 hours a day. A 22 kW home standby generator running 8,000 W costs about $5.50 an hour on propane or $3.08 on natural gas.
The same generator in every state
A 7,500 W portable gasoline generator running 3,000 W, 10 hours a day for 3 days, at each state's gasoline price (state or regional, EIA week of 2026-11-09).
| Alabama | $2.06 | $61.89 |
|---|---|---|
| Alaska | $2.72 | $81.50 |
| Arizona | $2.72 | $81.50 |
| Arkansas | $2.06 | $61.89 |
| California | $3.30 | $98.89 |
| Colorado | $2.22 | $66.60 |
| Connecticut | $2.41 | $72.18 |
| Delaware | $2.46 | $73.71 |
| District of Columbia | $2.46 | $73.71 |
| Florida | $2.21 | $66.25 |
| Georgia | $2.14 | $64.17 |
| Hawaii | $2.72 | $81.50 |
| Idaho | $2.34 | $70.16 |
| Illinois | $2.29 | $68.77 |
| Indiana | $2.29 | $68.77 |
| Iowa | $2.29 | $68.77 |
| Kansas | $2.29 | $68.77 |
| Kentucky | $2.29 | $68.77 |
| Louisiana | $2.06 | $61.89 |
| Maine | $2.41 | $72.18 |
| Maryland | $2.46 | $73.71 |
| Massachusetts | $2.37 | $71.24 |
| Michigan | $2.29 | $68.77 |
| Minnesota | $2.28 | $68.43 |
| Mississippi | $2.06 | $61.89 |
| Missouri | $2.29 | $68.77 |
| Montana | $2.34 | $70.16 |
| Nebraska | $2.29 | $68.77 |
| Nevada | $2.72 | $81.50 |
| New Hampshire | $2.41 | $72.18 |
| New Jersey | $2.46 | $73.71 |
| New Mexico | $2.06 | $61.89 |
| New York | $2.44 | $73.18 |
| North Carolina | $2.14 | $64.17 |
| North Dakota | $2.29 | $68.77 |
| Ohio | $2.23 | $66.99 |
| Oklahoma | $2.29 | $68.77 |
| Oregon | $2.72 | $81.50 |
| Pennsylvania | $2.46 | $73.71 |
| Rhode Island | $2.41 | $72.18 |
| South Carolina | $2.14 | $64.17 |
| South Dakota | $2.29 | $68.77 |
| Tennessee | $2.29 | $68.77 |
| Texas | $2.02 | $60.59 |
| Utah | $2.34 | $70.16 |
| Vermont | $2.41 | $72.18 |
| Virginia | $2.14 | $64.17 |
| Washington | $2.89 | $86.66 |
| West Virginia | $2.14 | $64.17 |
| Wisconsin | $2.29 | $68.77 |
| Wyoming | $2.34 | $70.16 |
How it works
The formula
fuel an hour = rated kW × (base + slope × load share)
cost = fuel × price
Assumptions
- Portable gasoline: base 0.0257 and slope 0.1333 gallons per rated kW, fitted to Honda's published run times for the EU2200i (0.95 gal tank: 3.2 h at rated load, 8.1 h at 1/4), EU3000iS (3.4 gal: 7.2 h and 20 h) and EU7000iS (5.1 gal: 6.5 h and 18 h). These are inverter generators, which throttle down at light load; open-frame models run at full speed and burn more at light loads.
- Home standby: fitted to Generac's 22 kW spec sheet (model 7042): propane 2.53 gal/h at 50% load and 3.9 at 100%; natural gas 228 cu ft/h at 50% and 327 at 100%. We scale by rated size.
- Prices: gasoline is EIA's latest weekly price for your state or region; propane is your state's average over winter 2025-26; natural gas is the state's 2025 average residential price per 1,000 cu ft.
- Starting surges from motors and compressors are brief and barely change fuel use; size for them with a generator size calculator.
Worked example: a 7,500 W portable
Running 3,000 W (fridge, furnace blower, lights, phones), 10 hours a day for 3 days
- Load: 3,000 ÷ 7,500 = 40%
- Fuel: 7.5 × (0.0257 + 0.1333 × 0.4) = 0.59 gal an hour
- Cost: 0.593 × $4.00 = $2.37 an hour, $23.71 a day, $71.12 for the outage (17.8 gallons)
Ways to cut the cost
- Run only what you need. Fuel use climbs with load; staggering the well pump, microwave and dryer cuts it.
- Don't oversize for small loads. A big generator running a few lights burns far more per kWh than a small inverter model.
- Store fuel safely. Keep gasoline in approved cans, add stabilizer, and rotate it every few months.
- Run it in cycles. A fridge stays cold for hours; running the generator a few hours on, a few off saves fuel.
- Carbon monoxide kills. Outdoors only, 20 ft from the house, with CO alarms inside.
Questions people ask
How much gas does a generator use per hour?
It depends on its size and how hard it's working. A 7,500 W portable generator running 3,000 W of appliances burns about 0.59 gallons an hour; at full load, about 1.19. A small 2,200 W inverter running 800 W uses about 0.16 gallons an hour. The rate climbs with the load, so turning off what you don't need stretches a tank.
How much does it cost to run a generator for a day?
At $4.00 a gallon (U.S. average, EIA week of 2026-11-09), the 7,500 W generator above costs about $23.71 for 10 hours. A 22 kW home standby unit running 8,000 W costs about $55.03 a day on propane or $30.82 on natural gas at average prices.
Is generator power more expensive than the grid?
Usually much more. The portable example works out to about $0.79 per kWh, against 18.16¢ from the grid. Generators are least efficient at light loads, so a big generator running a few lights costs the most per kWh.
How long will a generator run on a tank?
Divide the tank size by the gallons per hour at your load. Manufacturers list run time at a quarter load and full load; Honda's EU3000iS, for example, runs about 20 hours at 1/4 load and 7 hours at full load on its 3.4 gallon tank.
Is it safe to run a generator in the garage?
No. Generator exhaust contains carbon monoxide, which can kill in minutes. Run it outdoors, at least 20 feet from the house with the exhaust pointed away from doors, windows and vents, and fit battery CO alarms inside. Never run it in a garage, even with the door open. Connect to the house only through a transfer switch or interlock installed by an electrician.