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Generator Fuel Cost Calculator

Work out what an hour of generator power costs, what each kWh from it costs, and what a week of outages adds up to — and how much more that is than power from the grid.

Fuel
kW
Rated output, from the label.
%
How much of its power you use.
gal/h
At this load. Typically 0.13–0.18 gal per kWh.
$/gal
U.S. average, EIA, Nov 9, 2026.
$/h
Oil and filters: about $8 every 50 hours.
h
¢/kWh
For comparison. U.S. average: 18.16 ¢/kWh, EIA, Nov 9, 2026.

One hour of running costs

$1.11

0.24 gal of fuel an hour · delivers 1.5 kW

1 kWh
$0.74
0.16 gal
Per day
$8.87
1.92 gal
Per month
$266
57.6 gal
Per week
$62.09
13.44 gal
Energy per day
12 kWh

A generator kWh costs about 4.1× more than grid power.

Generator$0.74
Grid$0.18

How the cost is calculated

Cost per hour = fuel use × fuel price + upkeep. A generator burning 0.24 gallons of gasoline an hour at $4.00 a gallon spends about $0.96 on fuel. Add around $0.15 for oil and filters and you get roughly $1.11 an hour.

Cost per kWh = cost per hour ÷ the power the generator actually delivers. A 3 kW generator at half load delivers 1.5 kW, so each kWh costs about $0.74 — several times the U.S. average grid rate of 18.16¢ (Aug 2026).

Gasoline, diesel or propane

  • Gasoline — the most common portable generators, 2–8 kW. Simple and affordable, but the highest fuel use per kWh, and gasoline goes stale in storage.
  • Diesel — more efficient per kWh and built for long runs, but the generator costs more and is louder.
  • Propane — burns cleaner and stores for years, and many standby and dual-fuel generators use it. It takes more gallons per kWh than gasoline.

Default prices are U.S. averages, EIA, Nov 9, 2026. Enter what you pay locally for a precise result.

How to spend less

  • Don't idle a big generator at 10–20% load: group heavy jobs like the well pump, laundry and recharging together.
  • Pair the generator with a power station: a few generator hours a day, the quiet station the rest of the time. How long will your station last?
  • Change the oil on schedule: a worn engine burns more fuel.

Frequently asked questions

How much fuel does a 3,000-watt generator use?

A 3 kW gasoline generator typically burns 0.2–0.3 gallons an hour at half load and 0.4–0.5 at full load. Check the manual: the figure is often given for 25%, 50% or 75% load.

Why is generator electricity so expensive?

A small generator turns only 15–25% of the fuel's energy into electricity; the rest becomes heat. So a kWh from it typically costs several times more than a kWh from the grid.

Is a generator or a power station cheaper?

A power station is charged from the grid at your normal rate, so each kWh is cheap, but its capacity is limited. A generator runs as long as you have fuel, but every kWh is expensive. A common mix: run the generator a few hours a day for heavy loads and to recharge the station, then let the station run quietly overnight.

At what load is a generator most efficient?

Usually at 50–75% of its rated output. At light loads it burns almost as much fuel while producing less power, so each kWh costs more.

Can I run a generator in the garage?

No — not even with the door open. Generators produce carbon monoxide, which is odorless and deadly. Run them outdoors only, at least 20 feet from the house with the exhaust pointed away from windows and doors, and keep a CO alarm inside.

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