Northshore Generators · Reference Chart
Whole Home Generator Fuel Consumption Chart
| Generator | Load | Natural gas (BTU per hr) | Liquid propane (gal per hr) |
|---|---|---|---|
| 22 kW Generac Guardian | 50% load (half load) | 228,000 | 2.53 |
| 22 kW Generac Guardian | 100% load (full load) | 327,000 | 3.90 |
| 24 kW Generac Guardian | 50% load (half load) | 203,000 | 2.53 |
| 24 kW Generac Guardian | 100% load (full load) | 306,000 | 3.90 |
Source: Generac Guardian Series manufacturer fuel consumption tables (models G007042 22 kW, G007210 24 kW). Natural gas BTU per hr calculated as ft³/hr × 1,000 per Generac engineering documentation.
Propane tank sizing and blackout runtime
Liquid propane tanks are rarely filled to the top for safety. Plan on about 80% of nameplate capacity as usable fuel (200 gallons from a 250 gallon tank, 400 gallons from a 500 gallon tank).
How long does a 250 gallon tank last?
For a typical 22kW Generac Guardian or 24 kW Guardian on propane during a continuous outage:
- Half load (2.53 gal per hr): roughly 79.1 hours of run time from a 250 gallon tank
- Full load (3.90 gal per hr): roughly 51.3 hours of run time from a 250 gallon tank
Real homes often cycle between these points as HVAC and appliances start and stop. A 250 gallon tank is a common minimum for whole home standby, but many installers recommend 500 gallons when you want several days of margin without a refill during a major storm.
500 gallon tank runtime (same units)
- Half load: about 158.1 hours continuous
- Full load: about 102.6 hours continuous
Natural gas notes
Homes on utility natural gas do not store fuel on site. The meter and gas line must deliver enough volume at full load (up to 327,000 BTU per hr for 22 kW, 306,000 BTU per hr for 24 kW per the table above). Your gas utility or installer confirms pipe sizing and regulator capacity before startup.
Planning real world fuel use
Half load figures assume roughly 50% of the generator's rated output. Full load figures assume maximum continuous output on propane (22 kW LP / 24 kW LP) or the rated natural gas output (19.5 kW NG / 21 kW NG). Exercise cycles and partial home backup use less fuel than continuous whole home loading.
Northshore Generators sizes and installs 22kW Generac Guardian and 24 kW units in St. Tammany Parish. See our installation cost guide or call 985-239-5996 for a site specific fuel and tank plan.