Generator Fuel for an Outage Calculator
Plan how much fuel a power outage takes — gallons, cans and cost from your run schedule and generator consumption.
How it works
run hours = outage days × hours run/day · fuel = run hours × gal/hr · cans = ⌈fuel ÷ can size⌉
Fuel need is run hours times the generator’s consumption rate, and consumption climbs with load — a portable unit might sip 0.5 gal/hr lightly loaded but drink 1.2+ at full output. Most households don’t run a portable generator around the clock; they cycle it to run the fridge, keep phones charged and a few lights, which stretches fuel and lets the engine cool. Because gas pumps also fail in an outage, the practical question is how many cans to keep safely stored and treated with stabilizer before the storm.
Worked example
A 2-day outage running the generator 12 hours a day is 24 run hours. At 0.75 gal/hr that’s 18 gallons — four 5-gallon cans — costing about $63 at $3.50/gal. Running it 24/7 instead would nearly double that to 36 gallons.
Frequently asked questions
How long can I safely store gasoline?
Untreated gasoline starts degrading in 1–3 months. With fuel stabilizer added, sealed cans keep for about a year. Rotate your stored cans into your car every few months so the reserve is always fresh when a storm hits.
Is it safe to refuel a running generator?
No — shut it off and let it cool first. Gasoline spilled on a hot engine can ignite. This is one reason to size cans and plan run cycles ahead, so refueling happens on your schedule during a cool-down, not in a panic.
How do I run a generator safely during an outage?
Only outdoors, well away from windows and doors — never in a garage or enclosed porch, even with the door open. Carbon monoxide from a generator kills quickly; keep it 20+ feet from the house and use a CO alarm indoors.
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This calculator is for educational purposes. Double-check important results before acting on them.