BuildMath

Whole house generator cost calculator

Size in kW, fuel, and extras. Totals are the sum of the cited ranges you leave on. Every line is editable.

Generator size
Fuel
Extras
$$
$$
Size a poured pad with the concrete calculator.
$/ft$/ft
For trench volume, use the cubic yard calculator.
$$
Add your electrician's quote
$$

You need $12,065 typical ($8,280–$15,850).

A licensed electrician must wire a standby generator. A licensed gas fitter must run the gas line. Most places also require a permit. This page is an estimate, not a bid.

ItemLowTypicalHigh
Generator unit$4,000$5,000$6,000
Automatic transfer switch$600$1,550$2,500
Concrete pad$150$275$400
Gas line (30 ft)$450$975$1,500
Permit$80$265$450
Labor$3,000$4,000$5,000
Total$8,280$12,065$15,850
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How we calculated this

Each total is the sum of the lines you left on. Typical is the midpoint of the low and high totals, not a third quote.

The unit default is HomeGuide’s 17–20 kW band, $4,000–$6,000 (December 30, 2025).

HomeGuide’s install labor is a bundled figure ($3,000–$5,000). If your installer already put the pad, switch, wiring, and gas line in that number, uncheck those extras or clear labor.

Electrical work has no cited lump range (HomeGuide lists wiring at $6–$8 per foot). It starts unchecked. Add your electrician's quote.

Installation needs a licensed electrician, a licensed gas fitter for gas lines, and a local permit. This is an estimate only. Prices are reviewed yearly.

Sources

Unit bands, diesel $5,000–$18,000 (2–24 kW), labor $3,000–$5,000 or $5,000–$12,000+ over 20 kW, automatic transfer switch $600–$2,500, precast pad $150–$400, gas line $15–$50+ per foot, propane tank $400–$1,800, permits $80–$450, and annual maintenance $200–$650 are from HomeGuide (cost guide, December 30, 2025) (opens in a new tab), Kristen Cramer. Electrical work has no lump on that page (wiring is $6–$8 per foot), so that extra starts unchecked.

26–32 kW units $6,500–$15,000: HomeAdvisor, Whole-house generator cost (cost guide, June 19, 2026) (opens in a new tab). HomeGuide has no 26 kW row; this page uses that HomeAdvisor band for 26 kW.

Automatic transfer switch $600–$2,500, national average $1,450, most jobs $1,200–$1,600: Angi (cost guide, October 16, 2026) (opens in a new tab). Whole-house install labor $1,500–$5,000, permits $50–$200, and a national average installed cost of $5,156 (most jobs $1,512–$8,803): Angi (cost guide, September 1, 2026) (opens in a new tab). Angi pad pricing is $50–$75 per square foot; this page uses HomeGuide’s precast $150–$400 instead.

Daily run cost for a 20 kW standby, $30–$40 on natural gas, $150–$170 on liquid propane, and $100–$120 on diesel, is from the same HomeGuide daily run table (cost guide, December 30, 2025) (opens in a new tab). Local fuel prices change those figures.

Permit required, licensed trades, fee $281: City of Baytown, Texas, Residential Standby Generator checklist (city, accessed October 24, 2026) (opens in a new tab). Installation needs a licensed electrician and a licensed gas fitter for gas lines. This is an estimate. Prices are reviewed yearly.

Whole house generator cost calculator

A 20 kW natural-gas standby, with an automatic transfer switch, a precast pad, a 30 ft gas line, a permit, and HomeGuide’s install labor, sums to $8,280–$15,850 on this page (typical $12,065). Electrical work stays empty until you have a quote. Those dollars are cited ranges, not a bid.

  1. Choose a size in kW, or type a custom size. 26 kW uses HomeAdvisor’s 26–32 kW unit band, $6,500–$15,000.
  2. Pick natural gas, propane, or diesel. A propane tank line appears only on propane.
  3. Check extras you need. Unchecking a line removes it from the low, typical, and high totals.
  4. Edit any range. Costs vary by region. If labor already includes the pad, switch, and gas line, uncheck those extras or clear labor so you do not double-count.

Each total is the sum of the lines that are on and have both a low and a high. Typical is the midpoint of those two totals, not a third quote. Gas-line dollars are the per-foot range times length.

How much does a whole house generator cost?

A whole-house standby generator often lands in a wide installed band. HomeGuide (cost guide, December 30, 2025) puts 17–20 kW units at $4,000–$6,000 and install labor at $3,000–$5,000 up to 20 kW, with an automatic transfer switch at $600–$2,500. Itemizing the unit, switch, pad, a 30 ft gas line, permit, and that labor on this page totals $8,280–$15,850 (typical $12,065); a bundled installer quote can be lower if those extras are already in labor (HomeGuide’s installed range for similar jobs is $6,000–$11,000).

Worked example: 20 kW natural gas standby

Worked example

Default job on this page: 20 kW natural gas, automatic transfer switch, precast pad, 30 ft gas line, permit, and install labor. Electrical work starts unchecked.

Unit $4,000–$6,000. Transfer switch $600–$2,500. Pad $150–$400. Gas line 30 × $15–$50 per foot = $450–$1,500. Permit $80–$450. Labor $3,000–$5,000. Electrical work is off until you add your electrician's quote.

Low: $4,000 + $600 + $150 + $450 + $80 + $3,000 = $8,280. High: $6,000 + $2,500 + $400 + $1,500 + $450 + $5,000 = $15,850. Typical is the midpoint, $12,065.

HomeGuide’s $6,000–$11,000 installed figure already bundles labor with much of that work. If your installer quotes that way, uncheck the extras that are already in labor.

Size a poured pad with the concrete calculator. For a gas-line trench, use the cubic yard calculator.

Transfer switch: what it does and what it costs

A transfer switch sits between the utility feed and the generator so only one source can energize the house. That prevents backfeeding the grid. Standby units use an automatic transfer switch: it senses an outage, starts the generator, and reconnects the panel.

HomeGuide (cost guide, December 30, 2025) lists automatic transfer switch installation at $600–$2,500, and transfer-switch work overall at $400–$2,500. Angi (cost guide, October 16, 2026) uses the same automatic band, $600–$2,500, with a national average of $1,450 and most jobs $1,200–$1,600. This page defaults to the automatic $600–$2,500 range because a whole-house standby needs an automatic switch. Type your quote if it differs.

Wiring from the generator to the panel is separate. HomeGuide lists electrical wiring at $6–$8 per foot, not as a lump, so Electrical work starts unchecked with an empty field for your electrician's quote.

Questions

How much does a whole house generator cost installed?
HomeGuide (cost guide, December 30, 2025) puts a typical whole-house standby at $6,000–$11,000 installed, or $9,500–$24,000 for long runs or systems over 20 kW. This calculator’s default 20 kW itemized total is $8,280–$15,850 (typical $12,065) because it adds the unit, switch, pad, 30 ft gas line, permit, and labor as separate lines. Angi (cost guide, September 1, 2026) reports a national average of $5,156, with most jobs $1,512–$8,803.
How much does installation cost?
HomeGuide lists install labor at $3,000–$5,000, or $5,000–$12,000+ for longer distances or units over 20 kW. Angi lists labor at $1,500–$5,000. Those labor figures often already include pad, switch, wiring, and gas work. If you keep labor on and also check those extras, the total will double-count unless you edit the ranges.
What size generator do I need for my house?
HomeGuide’s size table treats 13–16 kW as a full home under 1,500 square feet, 17–20 kW as 1,500 to 3,000 square feet, and 22–25 kW as 3,000 to 5,000 square feet. That is coverage guidance, not a load calculation. Size from running watts plus the largest starting watts, with margin, on the generator size calculator.
Is natural gas or propane cheaper to run?
On HomeGuide’s daily run table, a 20 kW standby is $30–$40 per day on natural gas and $150–$170 per day on liquid propane (local fuel prices change the number). Diesel for that size is $100–$120 per day. Natural gas needs a utility line; propane needs a tank ($400–$1,800 on this page when propane is selected).
Do I need a permit for a standby generator?
Usually yes. HomeGuide puts permits at $80–$450. Angi lists $50–$200. The City of Baytown, Texas (city checklist, accessed October 24, 2026) requires a residential standby-generator permit at $281 ($30 processing, $84 plan review, $167 permit) and licensed electrical and plumbing work. Your city’s fee is the one that counts; type it on the permit line.
How long does a standby generator last?
HomeGuide (December 30, 2025) lists 15 to 30 years, or 10,000 to 30,000 hours, with proper maintenance. Annual maintenance on that page is $200–$650.

Written by The BuildMath team. Formulas tested against worked examples. Updated October 24, 2026.