A 20 lb propane tank will run a 7,500-watt generator for roughly 3 to 5 hours, depending on the actual load on the generator at the time.

A 20 lb propane tank holds approximately 4.7 gallons of liquid propane, which contains around 430,000 BTUs of usable energy. A 7,500-watt generator running on propane consumes roughly 1.0–1.4 gallons per hour under a 50–75% load — the typical range during real outage use. At full load the tank depletes faster; at 25% load you may stretch past 5 hours. Propane output on dual-fuel generators also runs about 5% lower than the gasoline-rated wattage, so a unit rated 7,500W on gas delivers closer to 7,125W on propane.

  • A 20 lb propane tank contains approximately 4.7 gallons of liquid propane.
  • A 7,500-watt generator consumes roughly 1.0–1.4 gallons of propane per hour at 50–75% load.
  • Estimated runtime on a 20 lb tank: 3–5 hours depending on generator load percentage.
  • Propane output is approximately 5% lower than gasoline output on dual-fuel 7,500-watt generators.
  • A 40 lb propane tank doubles available runtime to roughly 6–10 hours under the same load conditions.