How Much Does a Whole House Generator Cost?

Common Range: $7,700 – $18,300, Installed

National Average: $11,325 | 18-20KW Generator Installed

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Average Installed Cost of Standby Backup Power Generators

The cost to have a whole house backup power generator installed costs around $6,900. This price includes a 7.5-10kw (kilowatts) generator that runs on natural gas, the electrical connections including an automatic power transfer switch and auto-start functionality when the power goes out, as well as installation of a natural gas line to fuel the generator and provide the wattage needed to power your home.

While this is considerably more than what you would spend on candles, flashlights, batteries and a wind up radio for emergencies, the benefits far outweigh the generator cost when you consider the food that may spoil in your refrigerator and freezer, having no heat, etc. If you have someone in the home that relies on electric powered medical equipment like an oxygen machine or dialysis machine, home power backup generators are essential to have.

Average Installed Costs

Average Do It Yourself cost
$750 (Portable, Not hard wired)
Average Contractor Installed Cost
$6,900 (7.5 – 10kw)
Average Contractor Installed Cost
$11,325 (18 – 20kw)
Typical Cost Average
$7,700 – $18,300

whole house standby generator installed at home

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Overview of Backup Power, Whole House Generators

When an electrical outage occurs, everyone wishes they had a backup generator. A small unit can supply power for home essentials like the refrigerator, furnace or small window AC unit and basic lighting for several days, or as long as your gasoline lasts. A large standby generator that runs on natural gas and is wired to power your entire home can produce all the electricity your home needs, so the household won’t miss a beat when the power goes out due to a storm or other electricity interruption. If you’re unsure, Popular Mechanics has a great comparison to decide if a standby generator is right for you.

This Costimate addresses whole house generators an the cost to have a generator installed at your home. The units are also called standby and backup generators, and our comparison above includes a portable generator that can be used to power select items on a temporary basis.  The information here will help you determine what size unit you’ll need, something an electrical contractor can and should do too. Generator installation cost is itemized for the labor and supplies required. Below, you can compare what we’ve discovered about standby generator installation costs with information from other sites and with actual costs submitted by homeowners. Our goal is to assist you in deciding if the backup generator installation cost is worth the benefits– keeping your home inhabitable, comfortable and safe while preventing the loss of perishable food.

natural gas backup generator

Backup Generator Cost Factors

While the price of the generator is the biggest expense, there are other factors that will determine your total standby generator installation cost. Let’s explore all of them.

  • The size of your home and what you plan to power – In order to provide power to your whole house, generators start at about 6,000 watts (or 6kW) and can be as large as 100,000 watts (100kW) for residential models, though very few homes require a unit larger than 30kW. A general rule is that you need 3-5 watts per square foot for essential electricity and 6-14 watts per square foot for whole-house electricity based on the number of appliances you have with high electrical demand. These include a sump pump, air conditioner, home security system, electric dryer, electric water heater, well pump, jetted tub, sauna, grow lights and a second refrigerator or freezer.
  • Whether the unit has a transfer switch or one must be added – The transfer switch senses the loss of power from the grid and automatically starts the standby generator. In most states, they’re required to connect a generator to your breaker panel.
  • How far from the electrical panel the unit is installed – The further away the generator is from the panel, the more time and materials are required and higher the total generator installation cost will be.
  • Whether a pad is needed – Costs are lowest when the generator is installed on concrete already in place, such as a patio. Costs go up for a DIY pad ($) or pad installed by a contractor ($$). Some homeowners want the generator installed in a garage since there is already a concrete floor and the unit will be out of the weather and safe from thieves. A few building inspectors permit indoor installation in a garage or outbuilding, but that is not recommended, even with vented exhaust. Since deadly carbon monoxide is a byproduct of natural gas and propane combustion, outdoor installation is the safe choice. Generator manufacturers recommend installation at least six feet from any window or other opening such as a dryer vent or furnace air intake.
  • A larger propane tank and/or extra propane (Optional) – If you use propane, a tank with 500-gallon capacity or more should be installed. Many propane sellers supply the tank free to customers, though minimum propane purchases apply. Plan to keep the tank nearly full (80% capacity is the maximum allowed) to have fuel necessary for a lengthy power outage. Most suppliers offer plans to regularly top off your tank, often with a price break since the propane is delivered as drivers make their rounds rather than making a trip out for one customer. If your home is equipped with natural gas, you might be able to have a plumber run a new gas line to the Generator and avoid propane.
  • Anti-theft equipment (Optional)– Some homeowners in high-crime areas install a cage around their generator that is anchored to the concrete slab. This option doesn’t pose the health risk of installing the unit in a garage.

If you decide to use a smaller generator for essentials, Honda has a great informational page about using smaller units to power your home during power outages. Additionally, Generac, one of the leaders in home power, has a good guide to the cost of one of their systems.

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Cost of Generator, Accessories & Installation Supplies

  • $1,875 – $4,900 | Generators up to 15kW (Total power for homes to approx. 2,500 sq. ft. / essential power for homes to 5,000 sq. ft.)
  • $3,500 – $12,500 | Generators from 15kW to 30kW (Total power for homes to approx. 5,000 sq. ft. / essential power for homes larger than 5,000 sq. ft.)
  • $9,700 – $24,000 | Generators larger than 30kW (Total power for homes larger than 5,000 sq. ft.)
  • $285 – $650 | Transfer switch, if not included with the generator
  • $40 – $300 | Concrete pad installed DIY or by a handyman
  • $650 – $1,750 | Refurbished propane tanks, 320-1,000 gallons (optional)
  • $1,000 – $2,500 | New propane tanks, 320-1,000 gallons (optional)
  • $1.85 – $3.00 per gallon | Current cost range of propane
  • $350 – $650 | Security cage for your generator and hardware (optional)

electricians tools and supplies

Permits, Inspection, and Related Costs

Permits and Inspection Cost

  • $150-$275 | Average costs for a permit to install a whole house generator and have it inspected to ensure it is properly and safely wired

Time to Install a Home Backup Power Generator

  • Up to 1 Hour | Planning the installation
  • 3-5 hours | Installation of a gas line
  • 6-10 Hours | Installation and wiring of the generator

Electrician Labor Costs

Whole house generator installation costs for electrical contractors range from $60-$100 per hour to wire the generator to the electrical panel plus the cost of wire and additional supplies. A gas line must also be installed, a job usually subcontracted to a plumber at similar hourly rates.

  • $1,800-$3,200 | Backup generation installation cost
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Here are several other common electrical projects related to installing a whole house backup power generator in your home.


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DIY or Hire a Pro

If all you need is a small portable 5kw generator to run the refrigerator, freezer, a few lights and power outlets, and possibly a gas furnace or small window ac unit, run extension cords or have an electrician setup your panel as needed, and call it a day.

If you want a whole house generator that can power 90-100% of your home on natural gas or propane, call a pro from the start. They’ll know which size is right for you, as well as handle the wiring of the automatic crossover switch and other electrical requirements to power your home properly.

We have a portable 5kw stored in the garage and use it regularly during storms and power outages as needed. I use the extension cord method since its the easiest due to the location of my breaker boxes. I spoke to an electrician a few months ago and he said he’d charge around $650, to install and wire a manual transfer switch that I can plug into outside, and turn off specific breakers to power only my essentials as needed.

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Common Questions and Answers

How Big of a Whole House Generator do You Need?

The size of a generator needed to run your whole house depends on many things. Home size, appliance use, the number of central air conditioners, and much more. Generac has a great calculator that allows you to size a generator properly for your needs.


Reviewed and Edited by Steve Hansen of Costimates

Last Updated: Friday, September 16, 2022

steve hansen of costimates-sm Steve Hansen is the Lead Editor of Costimates. (Learn more) An avid home improvement professional with more than 35 years experience in both DIY projects, as well as working as a construction foreman in residential new home building, upfits, repairs and remodeling.

"Like most homeowners, I became frustrated with the lack of quality information available on specific home improvement repairs and renovations. In 2015, Costimates was formed to help homeowners learn as much as possible about various projects and their costs so they could make better financial decisions."