Question 1

How long will a generator run on a tank of fuel?

Accepted Answer

It depends on the load. Fuel burn scales with how much power you draw, so a generator at half load lasts far longer than one at full load. Runtime equals the fuel you have divided by the burn rate at your load — a small portable might run 8–12 hours on a tank at moderate load, while a heavily loaded unit drains the same tank in a few hours.

Question 2

Why does runtime depend on load?

Accepted Answer

An engine burns fuel roughly in proportion to the power it produces. Run the generator at 25% load and it sips fuel; run it near its rating and consumption climbs sharply. That's why the same fuel supply can last twice as long simply by shedding non-essential loads.

Question 3

Does fuel type change runtime and cost?

Accepted Answer

Yes. Gasoline, propane, and diesel carry different amounts of usable energy per gallon — diesel is the densest and most efficient, propane the least — so the gallons-per-hour and cost-per-hour differ for the same load. A natural-gas standby unit isn't limited by a tank at all; it runs as long as the utility supply holds.

Question 4

How can I make my fuel last longer in an outage?

Accepted Answer

Run only essential loads, cycle the generator off when you don't need power, and keep it loaded efficiently rather than idling under a tiny draw. Always operate it outdoors, well away from windows and doors, and refuel only after it has cooled — gasoline on a hot engine is a fire hazard.

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