Fuel Consumption: Generac 22kW, 24kW, 26kW, and 28kW Generators
Fuel consumption is one of the most important practical considerations for standby generator ownership, especially for propane-fueled systems where tank size determines total runtime. Generac publishes rated consumption at full load and half load for both propane and natural gas. Here are the specific numbers for every model in the 22kW to 28kW range, along with practical guidance on tank sizing and real-world fuel costs.
Propane (LP) Consumption
The Generac 22kW consumes approximately 3.5 gallons of propane per hour at full load and approximately 1.8 gallons per hour at half load. The 24kW consumes approximately 3.8 gallons per hour at full load and approximately 2.0 gallons per hour at half load. The 26kW consumes approximately 4.1 gallons per hour at full load and approximately 2.2 gallons per hour at half load. The 28kW consumes approximately 4.4 gallons per hour at full load and approximately 2.4 gallons per hour at half load.
Natural Gas Consumption
The Generac 22kW consumes approximately 245 cubic feet of natural gas per hour at full load and approximately 140 cubic feet per hour at half load. The 24kW consumes approximately 280 cubic feet per hour at full load and approximately 160 cubic feet per hour at half load. The 26kW consumes approximately 380 cubic feet per hour at full load and approximately 222 cubic feet per hour at half load. The 28kW consumes approximately 410 cubic feet per hour at full load and approximately 240 cubic feet per hour at half load.
Real-World Consumption vs. Rated Maximum
Full load consumption represents the worst-case scenario where the generator is producing its maximum rated output continuously. In practice, residential generators operate at 30% to 75% of capacity during a typical outage. The AC cycles on and off. The water heater heats to temperature and shuts off. Lights and electronics draw modest power. This cycling behavior means actual consumption during a typical outage runs much closer to the half-load figures than the full-load maximums.
Propane Tank Sizing for Each Model
For the 22kW at typical residential load (approximately 2.0 gallons per hour average), a 250-gallon tank (200 usable gallons) provides roughly 4 days of continuous operation. A 500-gallon tank (400 usable gallons) provides roughly 8 days. A 1,000-gallon tank provides roughly 16+ days. For the 26kW at typical load (approximately 2.5 gallons per hour average), a 500-gallon tank provides roughly 6 to 7 days and a 1,000-gallon tank provides roughly 13+ days. For hurricane-zone homes or areas with historically long restoration times, a 500-gallon tank is the recommended minimum for any model in this range.
Natural Gas: Unlimited Runtime
If your home has utility natural gas service, fuel supply is effectively unlimited. Natural gas is delivered continuously through underground pipes that operate independently of the electrical grid. Your generator runs for the entire duration of the outage, whether that is 4 hours or 4 weeks, with no fuel management on your part. This is the primary advantage of natural gas as a generator fuel.
Estimated Fuel Cost During an Outage
At an average propane price of $2.50 per gallon, operating a 22kW generator at typical residential load costs approximately $5.00 per hour, $120 per day, or $840 per week. At an average natural gas rate of $1.50 per therm, operating the same 22kW generator at typical load costs approximately $2.10 per hour, $50 per day, or $350 per week. Natural gas is typically 50% to 60% less expensive to operate than propane. These costs are modest compared to the financial impact of an unprotected extended outage (spoiled food, hotel stays, lost work income, potential property damage).
Does Higher Wattage Mean Proportionally Higher Fuel Use?
Not exactly. The 28kW model uses approximately 25% more fuel than the 22kW model at full load. However, if both generators are powering the same house with the same loads, they consume nearly the same fuel because the load determines consumption, not the generator rating. A 28kW generator powering a 15kW load uses approximately the same fuel as a 22kW generator powering the same 15kW load. The larger generator simply has more reserve capacity available.
Browse the full range at our Generac home standby generators 10kW to 28kW collection or call (800) 674-9019 for help choosing the right size and fuel type.