Home energy · backup power
Generator fuel needed calculator.
Enter the load you will run, the hours of outage and the fuel, and get litres, US gallons, jerry cans and tank hours.
Inputs
Fuel for the outage
Enter the numbers above.
How much fuel does a generator need?
Fuel needed = electricity delivered divided by the share of the fuel’s energy the generator turns into electricity. Electricity is watts x hours / 1,000 kWh, and 1 kWh is 3,412 Btu. The U.S. Energy Information Administration lists 120,214 Btu per US gallon of gasoline, 137,381 for diesel and 91,452 for propane. The efficiency box is your assumption, not a published figure: small portable generators waste most of the fuel as heat, so the default is a low 10 percent. Use the fuel-consumption table in your manual if it has one.
Worked example. A 2,000 W load for 24 hours is 48 kWh = 163,776 Btu. For gasoline at 10 percent efficiency: 163,776 / (120,214 x 0.10) = 13.6 US gallons = 51.6 litres, about 2.15 L per hour. That is three 20 L cans; a 15 L tank would run about 7 hours.
Public Safety Canada says to run portable fuel-burning generators at least 6 m (20 ft) from all homes or buildings, with the exhaust directed away from open windows and doors; Ready.gov says outdoors and at least 20 feet from windows, doors and attached garages, and to let the generator cool before refuelling. A generator may only be connected to your home’s wiring through an approved transfer panel and switch installed by a qualified electrician; never plug it into a wall outlet.
Frequently asked questions
How much gas does a generator use per hour?
It depends on the load and the machine. For a 2,000 W load at 10 percent efficiency this tool gives about 2.15 litres (0.57 US gallons) of gasoline per hour. The manual’s consumption table for your model is better than any estimate.
What efficiency should I use?
There is no single published figure; it varies by model and load. A low value such as 10 percent gives a cautious (larger) fuel estimate. Raise it only if your manual’s numbers support it.
How far from the house should a generator be?
Public Safety Canada says at least 6 m (20 feet) from all homes or buildings, with exhaust directed away from open windows and doors. Ready.gov says outdoors and at least 20 feet from windows, doors and attached garages.
Does this cover how long fuel can be stored?
No. Follow the fuel container labels and your generator manual for storage and refuelling.
Does it work for a propane tank in pounds?
It uses US gallons of liquid propane. Tank sizes in pounds are not converted here; check the label or your supplier.
Sources
Checked
- U.S. Energy Information Administration, "British thermal units (Btu)", opened 8 October 2026. gasoline 120,214 Btu per gallon, diesel 137,381, propane 91,452, 1 kWh = 3,412 Btu
- Public Safety Canada, Get Prepared, "How to prepare before a power outage" (page dated 12 March 2026), opened 8 October 2026. generator 6 m (20 ft) from buildings, transfer panel and switch, no extension cords unless rated
- Ready.gov, "Power Outages", opened 8 October 2026. generators outdoors and 20 feet from windows, doors and attached garages, let it cool before refuelling
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Safety note
Generators produce deadly carbon monoxide and can cause electrocution and fires. Follow the manufacturer’s instructions and local rules, use working carbon monoxide alarms, and get a licensed electrician to connect a generator to a house. Check your local fire code and the container labels for how much fuel you may store at home. Fuel estimates are planning figures only.