The current Generac 18kW air-cooled standby generator sits in a useful middle ground between essential-load systems and the larger 22-28kW whole-house models.
Current published output is:
- 18 kW on liquid propane
- 17 kW on natural gas
Current published weight:
426 lb
Current enclosure dimensions:
46.4 × 26.3 × 30.7 inches
The current model uses:
- G-Force 800 engine
- Power Zone 200 controller
- Aluminum enclosure
- Cellular Mobile Link connectivity
- 80A main line circuit breaker
Generac 18kW questions answered: sizing, cost, fuel and maintenance
Generac 18kW Specifications (Manufacturer Data)
| Specification | Generac 18kW | Source |
|---|---|---|
| Models covered | G007259 (generator only); G007324 bundle with 200 A service-entrance transfer switch | 1, 2 |
| Rated output, natural gas | 17 kW | 3, 1 |
| Rated output, propane (LP) | 18 kW | 3, 1 |
| Engine | Generac G-Force 800, 2 cylinders, 817 cc, 3,600 rpm | 3 |
| Dimensions (L × W × H) | 46.4 × 26.3 × 30.7 in (117.9 × 66.8 × 77.9 cm) | 3, 1 |
| Unit weight | 426 lb / 193 kg | 3, 1 |
| Sound level | 65 dB(A) at 23 ft (7 m), normal load; 55 dB(A) in Quiet-Test low-speed exercise (measured from the front of the generator) | 3 |
| Natural gas use, ½ load / full load | 164 / 235 ft³/hr | 3, 1 |
| Propane use, ½ load / full load | 1.65 / 2.87 gal/hr (60 / 105 ft³/hr) | 3, 1 |
| Main line circuit breaker | 80 A | 3, 1 |
| Transfer switch options | Bundle G007324 includes a 200 A service-entrance-rated automatic transfer switch with integrated surge protection (NEMA 3R, US only) | 3 |
| Warranty | 5-year limited warranty, generator and transfer switch | 3, 1 |
| Starting MSRP | $5,709 generator only; $6,769 with transfer switch (G007324) | 1, 2 |
What the size and fuel figures mean for installation
Generac lists the 18kW for installation as close as 18 in (457 mm) to a structure, away from doors, windows and fresh-air intakes and subject to local code; the spec-sheet drawing is approximate, so the pad is laid out from the installation manual. On propane, 1.65 gal/hr at half load is roughly 119 gallons over a 72-hour outage (our arithmetic: 1.65 × 72); on natural gas the line and meter must carry 235 ft³/hr at full load alongside other gas appliances. See the propane tank sizing guide and gas line sizing guide. (Source: 3.)
Specification sources, checked October 3, 2026:
How Much Natural Gas Does a Generac 18kW Use?
Current published natural-gas consumption:
- 164 ft³/hr at 50% load
- 235 ft³/hr at full load
Rated natural-gas output:
17 kW
That one-kilowatt derate matters when comparing it with the headline 18kW rating.
How Much Propane Does a Generac 18kW Use?
Current published propane consumption:
- 1.65 gal/hr at 50% load
- 2.87 gal/hr at full load
Rated propane output:
18 kW
Is 18kW Enough for a Whole House?
Sometimes.
"Whole house" is not a generator size.
It depends on the actual simultaneous loads.
An 18kW generator may comfortably support a house with:
- One central AC
- Refrigerator/freezer
- Lighting
- Outlets
- Gas furnace
- Electronics
- Selected kitchen loads
especially with load management.
It may not comfortably support unrestricted simultaneous use of:
- Multiple AC units
- Electric heat
- Large electric water heater
- Pool equipment
- Electric range
- Dryer
- EV charging
without load management.
18kW and Central Air Conditioning
The previous-generation 18kW Guardian was marketed as capable of starting a five-ton air conditioner in appropriate installations.
The current answer still depends on:
- Compressor LRA
- Soft-start equipment
- Other simultaneous loads
- Fuel type
- Load management
Do not size the whole system from AC tonnage alone.
Generac 18kW Weight
Current model:
426 lb
That is generator weight, not total installed project weight.
Installation also involves:
- Pad
- Transfer switch
- Electrical work
- Fuel piping
- Possible surge/load-management equipment
Generac 18kW Dimensions
Current enclosure:
46.4 in L × 26.3 in W × 30.7 in H
That compact footprint is one reason the current air-cooled line can cover a broad power range without moving into a much larger liquid-cooled platform.
Generac 18kW Cost
Generac's current 18kW transfer-switch bundle is listed with MSRP starting around:
$6,769
That is not the installed price.
Installed cost also depends on:
- Transfer switch
- Electrical labor
- Gas plumbing
- Trenching
- Pad
- Permits
- Meter upgrades
- Load management
- Site difficulty
18kW vs 22kW
The current 22kW gives:
- 22 kW LP
- 21 kW NG
versus:
- 18 kW LP
- 17 kW NG
for the 18kW.
That is a meaningful 4kW step on both fuels.
The 22kW is the better choice when that extra capacity has a specific job.
18kW vs 14kW
The 18kW gives:
- +4 kW output on propane
- +3 kW output on natural gas compared with the current 14kW
The 18kW also gives more headroom for HVAC and overlapping household loads.
Who Should Buy the 18kW?
The 18kW makes sense when:
- 14kW is tight
- 22kW is unnecessary
- You want one major HVAC load plus normal household loads
- Natural-gas capacity supports it
- Load management can control secondary heavy loads
It is a strong "right-sized" option.
Who Should Skip It?
Move up if:
- Two large AC systems must run freely
- Electric heat is a major backup load
- You want minimal load management
- Calculated peak demand needs more than 17kW NG / 18kW LP
Move down if:
- You only need critical circuits
- HVAC requirements are modest
- Fuel-system upgrades dominate the project economics
Warranty and Maintenance
Current Generac standby generators carry a five-year limited warranty headline.
Maintenance intervals depend on runtime and model generation.
Current next-generation air-cooled models use longer normal service intervals than many older Guardians.
Bottom Line
The current Generac 18kW is a sensible middle-of-line machine:
18 kW LP / 17 kW NG, 426 lb, 46.4 × 26.3 × 30.7 in
The buying decision comes down to whether 17kW on natural gas or 18kW on propane actually covers your simultaneous loads.
If it does, you do not need to buy 22kW just because the number is bigger.
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