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Generator Runtime Calculator

Estimate how long a standby propane generator will run on a single tank, by load percentage and burn rate.

Inputs

Most generators are not rated to draw the tank below ~20%. Default 0.8 is conservative.

Pulled from the generator spec sheet — typically labeled "LP fuel consumption at 50% load".

133.3 hr

estimated runtime

How we got this
  • 5.6 days

    Runtime

  • 1.5 gph

    Burn rate at this load

  • 200 gal

    Usable gallons

Methodology

Runtime = usable gallons ÷ burn rate at the chosen load.

  1. Usable gallons: 250 gal × 0.8 = 200 gal. The cap reflects the safe-fill maximum (~80% liquid) and a typical low-fuel cutoff at the regulator.
  2. Burn rate scaling: most propane standby generators publish a single GPH number at 50% load (here, 1.5 gph). At 50% load, effective burn ≈ 1.5 × (0.4 + 1.2 × 0.50) = 1.5 gph.
  3. Runtime: 200 ÷ 1.5 = 133.3 hours (~5.6 days).

For a precise number under your real load profile, use the manufacturer's published load-vs-consumption curve.

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