Read the manual thoroughly and understand all of the instructions, cautions, and warnings before using this equipment. If any section of the manual is not understood, contact your nearest authorized dealer, or contact Generac Customer Service at 1-888-436-3722 (1-888-GENERAC), or www.generac.com with any questions or concerns. 

How much fuel is required to back up my home?

Fuel consumption depends on the generator power rating (kW), load, and fuel type. The information below can also be found in the specification sheets and product brochures.

Understanding fuel consumption equations

Fuel consumption equations help convert the amount of gas a generator uses (measured in cubic feet per hour or cubic meters per hour) into energy output, which is measured in BTUs (British Thermal Units) or megajoules. These conversions are essential for ensuring your fuel supply is properly sized to meet the demands of the generator and your home.

For natural gas:
To estimate how much energy your generator consumes:

• Multiply cubic feet per hour (ft³/h) by 1,000 to get BTU/h.
• Multiply cubic meters per hour (m³/h) by 37.26 to get megajoules per hour (MJ/h).

For liquid propane gas (vapor):

• Multiply cubic feet per hour (ft³/h) by 2,500 to get BTU/h.
• Multiply cubic meters per hour (m³/h) by 93.15 to get megajoules per hour (MJ/h).

These formulas help size fuel supply lines, regulators, and meters to make sure your generator gets enough fuel to run efficiently under load. Always consult the generator’s spec sheet or fuel data decal for exact values.

How can I calculate the average fuel cost and usage for my home?

Fuel consumption varies based on the load, kW size of the generator engine, and the fuel type. To calculate this, the homeowner must know:

• (A) The size of the generator you have installed
• (B) The fuel type used
• (C) What appliances you would need to power and their required wattage (load)
• (D) How long those appliances need to be powered
• What the local utility company charges for a given fuel type

Scenario example

Taylor wants to be prepared for a category 4 hurricane that's forecasted to make landfall next week. He has a (A) 10kW home standby generator that runs on (B) Liquid Propane. To conserve fuel and plan for the possibility of an extended outage, he needs the generator to supply power only to his most essential appliances: his A/C unit, fridge, and sump pump.

First, he adds up the total electrical load demands, in kilowatts, of all 3 of the appliances he plans to power with his generator:

• A/C unit: 2,250 watts
• Fridge: 750 watts
• Sump Pump: 2000 watts
  
• (C) Total: 5000 watts

Adding up the running watts, Taylor concludes that his 10 kW generator will need to continuously supply 5000 watts (or 5 kW) of power. Because his generator is 10 kW, and his load demands are 5 kW, Taylor's generator will be running at half load.

1. Taking past experience into account, Taylor estimates that category 4 hurricanes in his area cause an average extended outage of 3 days (D). He wants to make sure that he has enough liquid propane in his tank to supply power to his essential appliances for at least this long.
2. Using the chart below, Taylor finds that his 10 kW Guardian Series Generator consumes .97 gallons of LPG (liquid propane) per hour when running at half load. To simplify, he rounds up to 1 gallon. This means that Taylor's generator will consume about 1 gallon of LPG every hour it's running at half load.
   
   Screenshot from the Guardian-series table shown in the below section
   
3. Using his fuel monitor, Taylor notes that he has 125 gallons of LPG in his fuel tank. If the outage lasts exactly 3 days, his generator will consume approximately 72 gallons of LP (not accounting for the required cool-down every 24 hours: Continuous use maintenance for home standby generators).
   

This means that Taylor has enough fuel to last him through the anticipated 3 day outage, and beyond if necessary.

Generator fuel consumption rates

These are approximate values. Use the appropriate spec sheet or fuel data decal for specific values. Always reference your generator's specific spec sheets or installation manual to verify fuel consumption. Verify gas meter is capable of providing enough fuel flow to include household appliances and all other loads.

Note: The fuel supply and pipe MUST be sized at 100% load BTU/h (Megajoule/h) rating.

Always see fuel data decal for the correct BTU/h or Megajoule/h, and required fuel pressures:

• Natural Gas:
  BTU/h = ft³/h × 1000
  Megajoules/h = m³/h × 37.26
• Liquid Propane Gas (Vapor):
  BTU/h = ft³/h × 2500
  Megajoules/h = m³/h × 93.15

* Natural gas is in m³/h / ft³/h
** Propane is in gal/h (LP) / L/h (LP) / ft³/h (LPV)
*** Values given are approximate

Note: As newer generator designs are developed, operating efficiency improves. This is why some generators consume less fuel, despite having a larger engine size. For example, the chart below shows the Guardian 26 kW uses less fuel at half load than the 22 kW model. This is due to gained efficiencies in the design of the engine and alternator combination. Similarly, the 18 kW has a lower BTU than the 14 kW. This is because the engine and alternator combination on the 18kW is more efficient than on the 14 kW.

* Natural gas is in m³/h / ft³/h
** Propane is in gal/h (LP) / L/h (LP) / ft³/h (LPV)
*** Values given are approximate