24 kW generator
Propane output for a 24 kW standby unit such as the Generac Guardian 24 kW is 24,000 W, while natural gas output is about 21,360 W. Ratings for other models vary slightly. Running on natural gas, it handles homes of up to 5,000 sq ft that have 3-ton central air.
For natural gas installs, the 24 kW runs from $10,689 in Arkansas up to $12,989 in Oregon. Labor costs by state draw on BLS wages, May 2025.
Will 24 kW cover your house? Find your size in three questions, and count the AC or well pump start.
What a 24 kW generator runs
| Loads running together | Running | Peak at a motor start | Natural gas | Propane |
|---|---|---|---|---|
| Essentials | 4.5 kW | 5.6 kW | runs | runs |
| Essentials and a 1 hp well pump | 6.5 kW | 8.5 kW | runs | runs |
| Essentials and a 2-ton central AC | 7.0 kW | 9.0 kW | runs | runs |
| Essentials and a 3-ton central AC | 8.0 kW | 10.5 kW | runs | runs |
| Essentials and a 4-ton central AC | 9.5 kW | 12.5 kW | runs | runs |
Listed as essentials are a microwave, a fridge, a freezer, lights, TV, a router, a 1/2 hp sump pump and the furnace blower. The "runs" figure means your running load stays below 80% of the rating. On top of that, it covers the largest motor start.
| Whole house load | Natural gas | Propane |
|---|---|---|
| No central air | up to 5,000 sq ft | up to 5,000 sq ft |
| Central AC, 3 ton | up to 5,000 sq ft | up to 5,000 sq ft |
| Central AC, 4 ton | up to 3,500 sq ft | up to 5,000 sq ft |
NEC 220.83 guides the whole house rows: lights and outlets at 3 VA for each sq ft, and kitchen and laundry circuits along with gas heat. No electric range, dryer or water heater is counted. Check your own house.
Fuel used per hour
| Load | Natural gas | Gas cost | Propane | Propane cost |
|---|---|---|---|---|
| 25% | 152 cu ft | $3.32 | 1.84 gal | $5.04 |
| 50% | 203 cu ft | $4.45 | 2.53 gal | $6.91 |
| 75% | 255 cu ft | $5.58 | 3.21 gal | $8.78 |
| 100% | 306 cu ft | $6.71 | 3.90 gal | $10.65 |
Generac's fuel table covers the Guardian 24 kW unit at half load and full load; the 25% and 75% figures are read in between those two. Costs come from EIA US average prices.
Hours per propane tank
| Tank | 25% load | 50% load | Full load |
|---|---|---|---|
| 120 gal | 52 h | 38 h | 25 h |
| 250 gal | 108 h | 79 h | 51 h |
| 500 gal | 217 h | 158 h | 103 h |
| 1,000 gal | 434 h | 316 h | 205 h |
Tanks fill to 80%.
Installed price
| Line, 24 kW | Natural gas | Propane | Basis |
|---|---|---|---|
| Generator | $6,729 | $6,729 | List price Generac posts for the 24 kW package, without the switch |
| Transfer switch | $1,060 | $1,060 | difference between Generac's prices with and without that switch |
| Electrician: switch, wiring, start-up | $3,000 to $5,500 | $3,000 to $5,500 | install ranges as published, with the US average hourly wage of $34.37 (BLS) applied |
| Fuel line | $500 to $2,000 | $800 to $2,500 | from the meter for gas; from the tank for propane |
| Pad and permit | $300 to $1,200 | $300 to $1,200 | composite pad or slab, local fees |
| Installed | $11,589 to $16,489 | $11,889 to $16,989 | propane leaves out the tank |
By state: whole house generator cost.
24 kW compared with other brands
| Brand | Model at 24 kW or next up | List price | Installed, natural gas | Page |
|---|---|---|---|---|
 Generac | Guardian 24 kW, with switch | $7,789 | $11,589 to $16,489 | Generac cost |
 Kohler | 26 kW 26RCA, with switch | $7,546 | $11,346 to $16,246 | Kohler cost |
Every unit's installed price adds the same four items: the permit, the pad, the gas line and the electrician. A unit sold without a switch also gets Generac's price for the nearest size switch added to it. Generac and Kohler's own pages supply the list prices. Cummins, Briggs & Stratton and Champion are sold by dealers, and the dealer quotes the unit: Cummins price, Briggs & Stratton price, Champion price.