Whole house generator cost calculator

Pick the generator size, add a transfer switch or gas line, and enter your ZIP. The price is the unit plus HomeAdvisor's installation, with each step shown.

$10,125Typical 20 to 25 kW, installed

$1,500 to $5,000Installation (HomeAdvisor)

$2,700 to $3,700Transfer switch (Fixr)

Generator installation cost

$7,000 to $13,250

Typical $10,125 (US average)

$7,000Low

$13,250High

Standby generators need a permit, a transfer switch and the right clearance from windows. Never run a portable generator indoors.

Free. Your numbers become an estimate you can send from your phone.

How we got this

20 to 25 kW (whole house)$7,000 to $13,250 (typical $10,125)Installation $1,500 to $5,000 (HomeAdvisor) plus the unit. Unit: Bob Vila $5,000 to $6,500 for 20 to 24 kW, Fixr $6,000 to $10,000 for 22 to 25 kW; middle of the two.
RegionUS average prices (no ZIP entered)Enter a ZIP to scale the labor part of the price to your state's wages.
Total$7,000 to $13,250, typical $10,125

Item	Qty	Low	Typical	High
Standby generator, 20 to 25 kW, installed	1	$7,000	$10,125	$13,250
Total		$7,000	$10,125	$13,250

Sources: Bob Vila, whole house generator cost; Fixr, backup generator cost; HomeAdvisor, generator installation cost; Fixr, gas line installation cost; HomeAdvisor, gas line installation cost; Bob Vila, gas line installation cost; BLS Occupational Employment and Wage Statistics, May 2025 (state and national files); US Census Bureau, 2020 ZIP Code Tabulation Area to county relationship file. Checked 2026-10-09.

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Key takeaways

Whole house generators vary a lot: HomeAdvisor's range is $1,512 to $8,803 and Fixr's $10,000 to $20,000.
The unit is most of the price, from about $2,000 for 7.5 to 10 kW to $15,000 or more for 26 kW and up.
Installation runs $1,500 to $5,000, HomeAdvisor says.
A transfer switch and a gas line are the extras that change quotes most.

Generator cost by size

Size	Unit (Bob Vila)	Unit (Fixr)	Installed, typical
7.5 to 10 kW	$2,000 to $3,500	$800 to $4,000 (7 to 12 kW)	$5,825
14 to 18 kW	$4,000 to $5,500	$3,500 to $5,000 (13 to 16 kW)	$7,750
20 to 25 kW	$5,000 to $6,500	$6,000 to $10,000 (22 to 25 kW)	$10,125
26 to 38 kW	$6,500 to $15,000	$10,000 to $20,000 (30 to 38 kW)	$16,125

Sizing a generator

HomeAdvisor's guide ties size to the home: essential systems for homes under 1,500 square feet at $2,000 to $3,500, and main systems for 3,000 to 5,000 square foot homes at $5,000 to $6,500 for the unit. Central air, well pumps and electric ranges push the size up. An electrician sizes it to your loads.

Transfer switch and fuel

Fixr puts a transfer switch at $2,700 to $3,700 with wiring and labor; many installers include it. Natural gas and propane units need a gas line: the gas line cost guide combines Fixr, HomeAdvisor and Bob Vila at about $272 to $1,350.

A worked example

A 20 to 25 kW generator at the US average comes to $7,000 to $13,250, about $10,125 typical, or about $10,723 with a gas line. Enter a ZIP to scale the 35% labor share.

Quoting generators

Load list on the estimate. What runs during an outage.
Pad, gas and permit lines.
Offer a service plan. Yearly service through Koira's maintenance plans.

Last checked October 9, 2026. More for your trade: how electricians run on Koira.

FAQ

How much does a whole house generator cost installed?

HomeAdvisor says $1,512 to $8,803, $5,157 average; Fixr says $10,000 to $20,000 for a full 18 kW system.

How much is installation for a standby generator?

HomeAdvisor says $1,500 to $5,000.

What size generator do I need for a whole house?

Many homes need 20 kW or more with central air. An electrician sizes it.

How much does a transfer switch cost?

Fixr says $2,700 to $3,700 installed with wiring.

Are portable generators cheaper?

Yes. Bob Vila puts portable generators at about $500 to $2,000.

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