10 kW generator
On propane, a 10 kW standby unit like the Generac Guardian 10 kW supplies 10,000 W, while natural gas output is about 8,900 W. Ratings for other models differ a little. Besides the essential circuits, a unit running on natural gas also handles a 1 hp well pump. Central air in a whole house means you need a bigger generator.
For natural gas installs, the 10 kW unit starts at $7,519 in Arkansas and climbs to $9,819 in Oregon. State labor costs follow BLS wages, May 2025.
Does 10 kW cover your house? Size it in three questions, including the start of the AC or well pump.
What a 10 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 | too small | runs |
| Essentials and a 3-ton central AC | 8.0 kW | 10.5 kW | too small | too small |
| Essentials and a 4-ton central AC | 9.5 kW | 12.5 kW | too small | too small |
On the essentials list you have a fridge, a freezer, lights, a microwave, TV, a router, the furnace blower and a 1/2 hp sump pump. Your running load stays under 80% of the rating for the "runs" figure. On top of that, the largest motor start is covered as well.
Using the NEC 220.83 load sheet, you'll see that no whole house example with central air fits 10 kW. Such a unit usually ends up on an essentials panel; your house may differ. Check your house.
Hourly fuel use
| Load | Natural gas | Gas cost | Propane | Propane cost |
|---|---|---|---|---|
| 25% | 88 cu ft | $1.93 | 0.71 gal | $1.95 |
| 50% | 101 cu ft | $2.21 | 0.97 gal | $2.65 |
| 75% | 114 cu ft | $2.50 | 1.23 gal | $3.34 |
| 100% | 127 cu ft | $2.78 | 1.48 gal | $4.04 |
Half load and full load come from Generac's fuel table on the Guardian 10 kW, and you read 25% and 75% in between. EIA US average prices set the costs.
Hours per propane tank
| Tank | 25% load | 50% load | Full load |
|---|---|---|---|
| 120 gal | 134 h | 99 h | 65 h |
| 250 gal | 280 h | 206 h | 135 h |
| 500 gal | 559 h | 412 h | 270 h |
| 1,000 gal | 1,119 h | 825 h | 541 h |
Tanks fill to 80%.
Cost after installation
| Line, 10 kW | Natural gas | Propane | Basis |
|---|---|---|---|
| Generator | $3,769 | $3,769 | The 10 kW bundle at Generac list price, with the switch taken out |
| Transfer switch | $850 | $850 | the spread between Generac's two listings, with and without the switch |
| Electrician: switch, wiring, start-up | $3,000 to $5,500 | $3,000 to $5,500 | install ranges as published, using the US average hourly wage of $34.37 (BLS) |
| Fuel line | $500 to $2,000 | $800 to $2,500 | propane line from the tank; gas line from the meter |
| Pad and permit | $300 to $1,200 | $300 to $1,200 | composite pad or slab, local fees |
| Installed | $8,419 to $13,319 | $8,719 to $13,819 | propane leaves out the tank |
Costs by state for whole house generators.
10 kW compared with other brands
| Brand | Model at 10 kW or next up | List price | Installed, natural gas | Page |
|---|---|---|---|---|
 Generac | Guardian 10 kW, with switch | $4,619 | $8,419 to $13,319 | Generac cost |
 Kohler | 14 kW 14RCA, plus a switch | $5,098 | $9,958 to $14,858 | Kohler cost |
Each unit gets the same four items added to its installed price: the pad, the permit, the gas line and the electrician. A unit sold without a switch also gets Generac's switch price for the closest size added. List prices come from Generac and from Kohler's own pages. Dealers sell Cummins, Briggs & Stratton and Champion, and each dealer quotes the unit: cost of a Cummins generator, cost of a Briggs & Stratton generator, cost of a Champion generator.