Whole House Standby Generators
A whole house generator (a standby generator) is a permanently installed unit that runs on natural gas or propane and starts by itself within seconds of an outage. It's the right buy if outages in your area run long, nobody wants to haul a portable out in a storm, or someone in the house can't go without power. Expect to spend $5,000 to $25,000 depending on size and installation, plus a service visit or two a year.
How a standby generator works
The generator sits outside on a pad, piped to your gas line or a propane tank and wired to an automatic transfer switch next to your main panel. The transfer switch watches utility power. When it drops, the switch starts the generator and moves your circuits over to it; when utility power returns, it switches the house back to the utility and the generator shuts down.
Most home units run on one fuel. Generac says each of its home standby units is designed to run on natural gas or liquid propane, and the installer sets it up for whichever you have.
Whole house or essential circuits
This is the first decision, and it sets the size and price.
Essential circuits. The transfer switch carries a short list: well pump, furnace, fridge, a few lights and outlets, maybe the sump pump. Generac sells essential-circuit transfer switches such as a 100 A unit with 16 circuits. Smaller generator, lower cost.
Whole house. A service-entrance-rated switch takes the entire panel, and Generac lists service-entrance-rated models up to 400 A. The generator has to be big enough for everything that might run at once, or the installer adds load management. Champion says a load management module can manage big 240-volt loads like ranges and dryers, which may let you buy a smaller unit.
Sizing by home size
HomeAdvisor ties standby sizes to typical home sizes:
| Generator size | Typical use | Unit cost |
|---|---|---|
| 7.5 to 10 kW | Essential and non-essential systems, homes under 1,500 sq ft | $2,000 to $3,500 |
| 14 to 18 kW | Critical systems, 1,500 to 3,000 sq ft | $4,000 to $5,500 |
| 20 to 24 kW | Main systems, 3,000 to 5,000 sq ft | $5,000 to $6,500 |
| 26 to 32 kW | Main systems plus extra appliances | $6,500 to $15,000 |
| 36 to 48 kW | Many high-demand loads | $14,000 to $21,000 |
Square footage is a rough guide. Central air, electric heat, a big well pump and an electric range push you up a size, and gas appliances pull you down. Champion says a home under or around 4,000 sq ft may typically be managed with its 14 kW unit. A dealer's load calculation beats any table, and our generator sizing page shows how the math works.
Fuel options compared
| Fuel | Notes |
|---|---|
| Natural gas | Unlimited supply as long as the utility keeps the gas on. Your gas meter may need an upgrade through the utility. Standby units run $2,000 to $21,000 |
| Propane | For homes without gas service. Needs a tank, which HomeAdvisor puts at $300 to $1,500. Run time depends on tank size and delivery schedule |
| Diesel | Uncommon on homes. Standby diesel units run $3,000 to $20,000 and need fuel storage and treatment |
For most homes the answer is simple: natural gas if you have it, propane if you don't.
What it costs to own
Running costs are real. HomeAdvisor estimates about $40 to $50 a day to run a 10 kW natural gas unit and about $90 a day at 21 kW running continuously.
Maintenance matters more than people expect. Generac recommends service every 6 months by an authorized dealer, and HomeAdvisor puts professional maintenance at $80 to $300 a year. Between visits, walk past it now and then and look at the status light. A unit that throws a fault in April is far better than one that won't start in a January ice storm. See the Generac error codes page if yours shows one.
What to skip
- Oversizing "just in case." HomeAdvisor's advice is to match the generator to your home's load, since extra capacity only drives up the bill.
- Buying the unit online and hunting for an installer later. Generac recommends an authorized dealer or licensed contractor to keep the job to local, state and national codes.
- Tucking it in a tight spot. Champion's placement rules say no closer than 5 feet to windows, doors or vents, and never under a deck.
- Liquid-cooled units you don't need. Above 30 kW, liquid cooling adds a few thousand dollars. Most houses don't need that class.
Install notes
Placement is the big variable. Champion allows a unit as close as 18 inches from the house wall where code allows, at least 5 feet from any opening. Keeping the gas pipe and the wire run short saves money, and Champion considers under 20 feet of each an optimal install. The unit usually sits on a pad or on graded pea gravel.
Expect a site survey, permits, a gas line, a transfer switch and an inspection. Generac says the install itself usually takes hours, but the prep and permits can take weeks. Our standby generator installation page walks through each step, and the whole house generator cost page breaks down the price.
FAQ
What is the best whole house generator?
The best one is the size your load calculation calls for, from a brand with a dealer near you who'll service it. Generac, Champion, Briggs & Stratton and Cummins all sell home standby units, with HomeAdvisor listing starting prices from about $2,000 for Champion to $6,000 for Generac. Local dealer support matters more than the logo, because the dealer handles the maintenance and warranty calls.
How much is a whole home standby generator?
HomeAdvisor puts standby generators at $5,000 to $25,000 including installation. Generac's own figure for a typical installed home standby generator is $8,000 to $16,000. Size, fuel, transfer switch type and the length of the gas and wire runs move the price.
What size diesel generator for home?
Size a diesel the same way as any standby: by the loads you'll run. The HomeAdvisor tiers above are a starting point, with 14 to 18 kW covering critical systems in many 1,500 to 3,000 sq ft homes. Diesel is rare on houses because of fuel storage, so most homes are better served by natural gas or propane.
Is a home standby generator a good investment?
It is if you lose power often or for long stretches, work from home, rely on a well or sump pump, or have medical equipment. HomeAdvisor says a standby generator often boosts home value, especially where outages and severe weather are common. If your outages are rare and short, a portable with an interlock gets you most of the benefit for much less.
How long do whole house generators last?
HomeAdvisor's natural gas generator guide gives a 15 to 30 year lifespan. Regular service is what gets a unit to the long end of that range, and Generac recommends a service visit every 6 months.
Sources
- GeneracHome Standby Generator FAQ (opens in a new tab)
- HomeAdvisorHow Much Does Whole-House Generator Installation Cost? (opens in a new tab)
- Champion Power EquipmentWhat a Site Survey Is and Why It Is Important When Purchasing a Home Standby Generator (opens in a new tab)
- GeneracBackup Generator Installation (opens in a new tab)
- GeneracStandby Generator Transfer Switches (opens in a new tab)
- HomeAdvisorHow Much Does a Natural Gas Generator Cost? (opens in a new tab)