Propane Consumption Rates for Standby Generators
A residential standby generator uses approximately 2 to 4 gallons of propane per hour at full load. Actual consumption varies based on the generator size, the electrical load being served, and ambient temperature. Since generators rarely run at full load continuously, real-world fuel consumption is typically 30% to 50% lower than the maximum rated consumption.
Consumption by Generator Size
Propane consumption scales with generator output. Here are approximate consumption rates at both full load and half load for common residential generator sizes.
A 10kW generator uses approximately 1.5 gallons per hour at full load and 0.75 gallons per hour at half load. A 14kW generator uses approximately 2.1 gallons per hour at full load and 1.1 gallons per hour at half load. A 16kW generator uses approximately 2.4 gallons per hour at full load and 1.2 gallons per hour at half load. A 20kW generator uses approximately 3.0 gallons per hour at full load and 1.6 gallons per hour at half load. A 22kW generator uses approximately 3.5 gallons per hour at full load and 1.8 gallons per hour at half load. A 24kW generator uses approximately 3.8 gallons per hour at full load and 2.0 gallons per hour at half load.
Real-World Usage vs. Full Load
Full load consumption represents the maximum fuel use when the generator is producing its rated output. In practice, residential generators operate at 30% to 75% of capacity during a typical outage. When the air conditioner cycles off, the load drops. When the stove is not in use, the load drops further. This cycling behavior means actual consumption averages closer to the half-load figures for most homes during a typical outage.
Propane Tank Sizing
Choosing the right propane tank ensures you have adequate fuel for extended outages without unnecessary cost. A 250-gallon tank (filled to the standard 80% capacity = 200 usable gallons) provides approximately 55 to 130 hours of runtime depending on generator size and load. For a 22kW generator at average load, expect approximately 80 to 100 hours, or roughly 3 to 4 days of continuous operation.
A 500-gallon tank (400 usable gallons) provides approximately 110 to 260 hours of runtime. For a 22kW generator, that translates to roughly 5 to 7 days of continuous use under typical conditions. A 1,000-gallon tank (800 usable gallons) provides approximately 10 to 14 days for most residential installations, which covers even the most extended outage events.
Estimating Fuel Cost
To estimate fuel cost, multiply the hourly consumption rate by the number of hours and by the current price per gallon of propane. If propane costs $2.50 per gallon and your 22kW generator runs at half load (1.8 gallons per hour), the fuel cost is approximately $4.50 per hour, $108 per day, or $756 per week of continuous operation. While not trivial, this cost is modest compared to the financial impact of an extended outage without power (spoiled food, hotel stays, lost productivity, and potential property damage from frozen pipes or sump pump failure).
Propane vs. Natural Gas Consumption
Propane contains approximately 91,500 BTU per gallon, while natural gas contains approximately 1,030 BTU per cubic foot. A generator that uses 3.5 gallons of propane per hour at full load would consume approximately 300 to 350 cubic feet of natural gas per hour to produce the same output. The key advantage of natural gas is that it is delivered continuously through utility infrastructure, so there is no tank to refill and no risk of running out during an extended outage. If your home has natural gas service, it is generally the preferred fuel choice for standby generators.
Keeping Your Tank Full
If your generator runs on propane, keep the tank at or above 50% capacity during outage-prone seasons. Many propane suppliers offer automatic delivery programs that monitor your usage and refill the tank on a schedule. Avoid waiting until an outage is in progress to request a fill, as propane delivery may be delayed during widespread weather events when demand surges.
IB Lighting carries propane-fueled and dual-fuel standby generators from Generac, Kohler, and Cummins. Call (800) 674-9019 to discuss fuel options and tank sizing for your installation, or browse our generator selection online.