The Best Whole House Generators
The best whole house (home standby) generators compared — by kW output, fuel type, transfer switch, running noise and warranty — with a pick for essentials backup and one for a large whole-home load.
A whole house generator — properly a home standby generator — is permanently installed outside your home, runs on natural gas or propane, and starts automatically within seconds of an outage, powering the whole house through an automatic transfer switch. The three names that matter in the US are Generac, Kohler and Cummins. Here’s how they compare, and which fits which buyer.
| Brand | Best for | Power range | Fuel | Transfer switch | Warranty |
|---|---|---|---|---|---|
| Generac | Whole-house standby (market leader) | 7.5–26 kW standby · 3,000–8,000 W portable | Natural gas or liquid propane (standby); gas & dual-fuel (portable) | Air-cooled standby pairs with a Generac automatic transfer switch | 5-year limited (air-cooled standby) |
| Kohler | Premium whole-house standby | 10–26 kW home standby | Natural gas or liquid propane | Pairs with Kohler RXT/RDT automatic transfer switches | 5-year / 2,000-hour limited (many home models) |
| Cummins | Standby with industrial engine heritage | 13–20 kW QuietConnect home standby | Natural gas or propane (home standby); diesel (industrial); Onan (RV) | Pairs with Cummins automatic transfer switches | 5-year limited (many home standby models) |
Our picks
Generac 24 kW Guardian
Best overall: the market-leading whole-house standby, widest dealer network, covers most homes including central AC. More on Generac →
Kohler 20RCA (20 kW)
Best premium: build quality and a corrosion-resistant enclosure for buyers who want an alternative to Generac. More on Kohler →
Cummins RS20AC (20 kW)
Best engine heritage: Cummins’ QuietConnect standby, tuned for lower running noise. More on Cummins →
How to choose a whole house generator
- Size (kW) first. Most homes need 18–26 kW for whole-house backup with central AC. Run your load through the generator sizing calculator, then have an electrician confirm.
- Fuel. Natural gas means unlimited runtime from your utility line; propane suits homes without gas service but runs from a tank.
- Transfer switch. A whole-house standby needs an automatic transfer switch — factor it into the install.
- Install & permit. Standby generators must be sized, permitted and wired by a licensed electrician (NEC). Budget $3,000–$5,000 for installation on top of the unit.
Estimates only. A whole-house standby must be sized with a load calculation and installed by a licensed electrician. Prices and specs change — confirm current details with a dealer. As an Amazon Associate we earn from qualifying purchases.
Frequently asked questions
What is the best whole house generator?
For most homes the best whole-house generator is a Generac Guardian in the 22–24 kW range — it leads the US standby market with the widest line-up and dealer network. Kohler is the main premium alternative on build quality, and Cummins is a strong third with its industrial engine heritage. The best one for you depends on your load and budget; size it with the sizing calculator, then compare Generac, Kohler and Cummins on the specs below.
What size whole house generator do I need?
To back up a whole house including central air conditioning, most homes need an 18–26 kW home standby generator, with 22–24 kW the common choice. Smaller homes or essentials-focused backup can use 10–18 kW. Size it to your total running load plus the largest starting surge — run your appliances through the generator sizing calculator, then have an electrician confirm with a load calculation.
How much does a whole house generator cost installed?
An installed whole-house standby generator typically runs about $7,000–$15,000: roughly $3,500–$6,000 for the unit and $3,000–$5,000 for installation (pad, transfer switch, gas hookup and electrical). A 22–24 kW Generac or 20 kW Kohler for an average home commonly lands around $9,000–$12,000 installed. Get several local quotes, as site conditions and gas runs move the price.
Is a whole house generator worth it?
If you live in a storm-prone area, work from home, have medical equipment, or a well and sump pump that must keep running, a whole-house standby is often worth it — it starts automatically within seconds and runs on your gas supply for days. If outages are rare and brief, a portable generator covering essentials is far cheaper and may be enough. Weigh the install cost against how often and how long your power actually goes out.