Home generator installation: what happens, step by step

A standby generator install usually runs: dealer site visit, permits, a level pad or gravel base, the gas line, a transfer switch wired next to your main panel, inspection, and a test startup. Generac says the install itself takes hours but the whole job often takes weeks. A licensed electrician does the wiring.[Generac]

Decide first: a standby generator makes sense if your outages run long or for days and you have natural gas or room for a propane tank. For short outages on a few circuits, a battery may do. Size it with the home backup sizing cheat sheet, check outages in your state, then call two dealers.

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Step-by-step installation process

Here is the usual order of work for a home standby generator, based on Generac's homeowner guide and its installation manual for 9 to 22 kW air-cooled units. Other brands follow a similar path, but your dealer's manual and your local code win.

  1. Size the generator and check your outage risk. List what must run in an outage and size it with the home backup sizing cheat sheet, then look up how long outages last in your state.[Generac]
  2. Book a dealer site visit. Generac says an authorized dealer does a free at-home consultation that covers where the unit goes, site requirements, fuel type and any HOA restrictions.[Generac]
  3. Choose a spot that meets clearances. The spot must be stable and well drained, with the clearances in the manufacturer manual: away from windows, doors, vents and air intakes, and not under a deck.[Generac manual]
  4. Pull the permits. Generac's installation guide tells installers to contact the local inspector or city hall and secure all required permits before installing.[Generac manual]
  5. Prepare the base. The dealer prepares the site with a concrete slab or a pea-gravel base.[Generac]
  6. Connect the fuel. A qualified professional connects natural gas or propane and checks that the gas meter or propane tank can supply the generator.[Generac manual]
  7. Install the transfer switch and wiring. A trained, licensed electrician installs the transfer switch next to your main breaker box and wires it to the generator.[Generac manual][Generac]
  8. Inspect, start up and test. After the inspection, the dealer starts the unit and simulates an outage to confirm it takes over. Register the product so the warranty is on file.[Generac]

One company often handles all of it. The dealer may use its own licensed electrician and gas fitter or bring in subcontractors. Ask who does each step and who pulls each permit.

Standby generator installation requirements

Placement is where most quotes differ. These are the numbers in Generac's installation guidelines for its 60 Hz, 9 to 22 kW air-cooled generators[Generac manual]. Other models and brands can differ, so check your unit's manual.

RuleGenerac 9–22 kW guideline
Front and ends3 ft clear
Rear (to the house)18 in, based on Southwest Research Institute testing, unless local codes require more
Overhead5 ft clear; not under a wooden deck or structure
Windows, doors, ventsNo operable windows, doors, vents or other openings near any point of the generator
HVAC fresh-air intakesAt least 10 ft away
Default code ruleNFPA 37 calls for 5 ft from openings and combustible walls unless its exceptions apply

Generac's spec sheet for its 10, 14 and 18 kW models says the same thing in plain words: thanks to SwRI testing, the unit can go as close as 18 inches to the house, but keep it away from doors, windows and fresh-air intakes[Generac spec sheet]. Generac also tells installers to use carbon monoxide detectors in the home[Generac manual].

  • Ground: stable and well drained[Generac].
  • Fuel: the closer to the gas line and meter, the lower the install cost[Generac]. Your gas meter or propane tank must be big enough for the generator plus your other gas appliances[Generac manual].
  • Noise and HOA rules: Generac's dealers check HOA restrictions during the site visit[Generac]. Local noise rules vary, so ask your city or county. We don't list noise limits because they change by place.

Permits and inspections

Generac's guide tells installers to contact the local inspector or city hall and secure all required permits before installing, and to follow NFPA 37, NFPA 70 (the National Electrical Code) and local codes[Generac manual]. Depending on where you live, that can mean separate permits for the electrical work and the gas line. Who pulls them, the fees and the wait vary by city and county, so ask your local building department. Ask your dealer to put "permits and inspection included" in the written quote.

The transfer switch: automatic vs manual

The transfer switch connects the generator to your home's wiring and keeps power from feeding back onto utility lines.

  • Automatic (standby): Generac says an automatic transfer switch detects an outage and signals the generator to start, it switches on within seconds, and it keeps running until utility power returns[Generac].
  • Manual (portable): you start a portable generator and flip the switch yourself. Generac's HomeLink manual switch is made for portable generators, prevents back-feeding, and can later be upgraded for a standby unit up to 11 kW[Generac HomeLink].
  • Whole home or essential circuits: a whole-home switch covers the main panel. An essential-circuit switch covers a chosen list, such as the furnace, well pump, fridge and lights[Generac HomeLink]. Which one you need depends on the generator size.

Comparing standby, portable and battery options? See best home generator: standby vs portable vs battery.

How long installation takes

Generac says the installation itself can take a matter of hours, but the full process often takes several weeks because of dealer availability, site preparation, the gas line and the permit[Generac]. Plan for three phases: the quote and permit wait, the install day or days, and the final inspection and startup. If you live where hurricane or winter storm season hits, book before the season starts.

How to find and vet a generator installer

We don't list installers, and we won't make up local pages. Here is how to check one yourself:

  1. Use the maker's dealer finder. Generac dealer locator or Kohler dealer finder.
  2. Check the license. Look the electrician or contractor up on your state's contractor or electrical licensing board site.
  3. Ask for insurance. Get proof of liability and workers' comp coverage.
  4. Get it in writing. The quote should list the generator model, transfer switch, pad, gas line length, permits, inspection and startup.
  5. Register the warranty. Generac tells owners to register the product, and it says incorrect installation can void the warranty[Generac manual].

What installation costs

Generac says a home standby generator costs $8,000 to $16,000 on average, installed, including the generator[Generac]. The biggest swings come from the generator size, the transfer switch, the gas line run and the pad. See our whole house generator cost and installation breakdown or Generac generator cost by model.

Generator or battery?

A standby generator suits long outages and whole-home loads if you have gas or propane. A battery station is quiet, can run indoors, and needs no fuel line or gas permit, but it runs out once its stored energy is used unless you recharge it. Compare them in best home generator and best portable power station.

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Do you need one where you live?

Outage length matters more than outage count. See power outages by state, built on U.S. EIA Form EIA-861 data for 2024[EIA], or jump to Texas, Florida or North Carolina.

FAQ

Can I install a standby generator myself?

Not the wiring or gas work. Generac's installation guide says only a trained and licensed electrician should do the wiring, and a qualified professional should connect the fuel. It also warns that incorrect installation can void the warranty. Most homeowners hire an authorized dealer that coordinates the whole job.

Do I need a permit for a home generator?

Almost always. Generac's installation guide tells installers to contact the local inspector or city hall and secure all required permits before installing, and to follow NFPA 37, NFPA 70 (the National Electrical Code) and local codes. Rules and fees vary by city and county, so ask your building department or dealer.

How close to the house can a generator be?

Generac says its 9 to 22 kW air-cooled models can sit as close as 18 inches to the house, because of testing by Southwest Research Institute, unless local codes say otherwise. Keep 3 feet in front and at the ends, 5 feet overhead, and never put it near windows, doors or vents.

How long does a generator installation take?

Generac says the installation itself can take a matter of hours, but the full process often takes several weeks once you add dealer availability, site prep, gas line work and the permit. Ask your dealer for a written timeline that includes the inspection date.

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