48 kW generator
A standby generator rated at 48 kW, such as the Generac RG04845, provides 48,000 W using propane and about 42,720 W using natural gas. Other models have slightly different ratings. Using natural gas, this unit supports a home up to 5,000 sq ft equipped with 3-ton central air.
For natural gas installs, the 48 kW price starts at $25,600 in Arkansas, then reaches $28,700 in Oregon. State labor costs come from BLS wages for May 2025.
Does 48 kW provide enough power for your house? Size it with three questions, including the AC or well pump start.
What a 48 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 |
Essential loads include a fridge, freezer, 1/2 hp sump pump, microwave, lights, TV, router and furnace blower. The “runs” figure keeps your running load under 80% of the generator's rating. It also covers the largest motor start.
| Whole house load | Natural gas or propane |
|---|---|
| No central air | up to 5,000 sq ft |
| Central AC, 3 ton | up to 5,000 sq ft |
| Central AC, 4 ton | up to 5,000 sq ft |
Whole house rows follow NEC 220.83, using 3 VA per sq ft for lights and outlets, plus kitchen and laundry circuits and gas heat. No electric range, dryer or water heater is included. Check your house.
Fuel use per hour
| Load | Natural gas | Gas cost | Propane | Propane cost |
|---|---|---|---|---|
| 25% | 201 cu ft | $4.39 | 3.00 gal | $8.19 |
| 50% | 336 cu ft | $7.37 | 4.20 gal | $11.47 |
| 75% | 472 cu ft | $10.34 | 5.40 gal | $14.74 |
| 100% | 607 cu ft | $13.31 | 6.60 gal | $18.02 |
Generac's fuel table lists half load and full load for the RG04845; 25% and 75% read in between those two figures. EIA US average prices are used for costs.
Hours per propane tank
| Tank | 25% load | 50% load | Full load |
|---|---|---|---|
| 120 gal | 32 h | 23 h | 15 h |
| 250 gal | 67 h | 48 h | 30 h |
| 500 gal | 133 h | 95 h | 61 h |
| 1,000 gal | 267 h | 190 h | 121 h |
A tank's fill level reaches 80%.
Installed price
| Line, 48 kW | Natural gas | Propane | Basis |
|---|---|---|---|
| Generator and transfer switch | $21,800 | $21,800 | estimate, sold through dealers |
| Electrician: switch, wiring, start-up | $4,200 to $7,700 | $4,200 to $7,700 | published install ranges, adjusted to match the US average hourly wage of $34.37 (BLS) |
| Fuel line | $500 to $2,000 | $800 to $2,500 | gas line running from the meter; propane line running from the tank |
| Pad and permit | $300 to $1,200 | $300 to $1,200 | composite pad or slab, local fees |
| Installed | $26,800 to $32,700 | $27,100 to $33,200 | propane leaves out the tank |
See whole house generator cost by state.
Sizes listed here: 38 kW generator, All sizes.