Generator installation contractors put in standby (whole-home) and portable-connection generator systems for homeowners and small commercial clients. Invoices typically cover the generator unit, transfer switch, electrical and gas connections, concrete or composite pad, permits, and commissioning. Many are licensed electricians, plumbers or gas fitters, or work as a small crew that subs out part of the job.
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Most installs are priced as a flat fee for a defined scope, built from equipment cost plus materials, labor, permits and a margin. Generator and transfer switch costs are usually passed through with a markup of 10 to 25 percent. Labor is estimated in crew-hours or days but quoted as a lump sum. Variable items such as trenching, gas line length and conduit runs are often priced per linear foot so that changes are easy to adjust. Service calls, repairs and annual maintenance are billed hourly or as a flat plan fee. Permit, inspection and utility coordination fees are listed as separate lines. Larger jobs are billed in stages: deposit at signing, equipment order, rough-in, and final after inspection and startup.
| Service | Priced | Typical range |
|---|---|---|
| Standby generator install labor (residential, 10-24 kW), unit not included | flat fee | $3,000-7,500 |
| Generator unit, 22 kW air-cooled (supplied by contractor) | each | $4,500-7,500 |
| Automatic transfer switch (100-200 amp) supply and install | each | $900-2,500 |
| Gas line extension (natural gas or propane), black iron or CSST | per linear foot | $15-45 |
| Electrical conduit and wire run, trenching included | per linear foot | $20-60 |
| Concrete or composite equipment pad | flat fee | $300-900 |
| Permit and inspection coordination | flat fee | $150-600 |
| Electrician or gas fitter labor, service and repair | per hour | $85-175 |
| Annual maintenance plan (oil, filters, plugs, load test) | per visit | $200-450 |
Typical US ranges. Rates vary by region, experience, and job size.
| Description | Qty | Rate | Amount |
|---|---|---|---|
| 22 kW air-cooled standby generator, model and serial no. on file | 1 each | $5,800.00 | $5,800.00 |
| 200 amp automatic transfer switch, supply and install | 1 each | $1,600.00 | $1,600.00 |
| Composite equipment pad, set and leveled | 1 flat fee | $450.00 | $450.00 |
| Natural gas line extension, CSST, including pressure test | 40 per linear foot | $28.00 | $1,120.00 |
| Conduit and wire run, trenched | 65 per linear foot | $32.00 | $2,080.00 |
| Installation labor, mounting, wiring, commissioning and startup | 1 flat fee | $3,800.00 | $3,800.00 |
| Electrical permit and inspection coordination | 1 flat fee | $350.00 | $350.00 |
| Total | $15,200.00 | ||
Notes: Deposit of $6,000 received at signing is credited above. Balance due within 10 days of passed final inspection. Generator warranty registered in the customer's name; manufacturer warranty terms apply. Unit has been tested under load and the owner was walked through operation and exercise settings.
Needed for warranty registration, insurance records and future service calls.
Documents what was installed and which circuits or whole-home loads it covers.
Many states and cities require license numbers on contracts and invoices, and permit numbers show the work was inspected.
Lists natural gas or propane, pipe type and length, pressure test results and any meter or regulator upgrade, which are common dispute points.
Helps with sales tax treatment, which varies by state, and shows the client where the money went.
Shows when the final inspection passed and when the system was started and load tested, which usually triggers final payment.
Rock, extra trenching, panel upgrades or longer gas runs should appear as separate lines tied to a signed change order.
Shows the remaining balance clearly on staged jobs.
A deposit of 30 to 50 percent at signing is common, since equipment is ordered up front and can be costly or non-returnable. Many contractors collect a second payment when the generator and transfer switch are delivered or the rough-in is complete, with the balance due on a passed inspection and startup, typically net 7 to 14 days. Large residential jobs are often paid by check, ACH or card, and some contractors add a card fee or offer a discount for ACH. Late fees of 1 to 1.5 percent per month are common if stated in the contract. Check your state's rules on deposit limits, lien rights and required contract language.
Generators are expensive, and lumping them in with labor invites arguments over price. Separate lines also protect you if the client cancels after the unit is ordered.
Supply delays and price changes are common. A deposit large enough to cover the unit and switch keeps you from financing a client's generator.
State in the contract that final payment is due after the passed inspection and startup, not after the client feels comfortable. It removes ambiguity about when you can send the last invoice.
Rock, tree roots, long gas runs, meter upgrades and panel replacements can swing a job by thousands. Write them up and get a signature before doing the work, then invoice them on their own lines.
Offer an annual service plan on the final invoice or at startup. Recurring plan invoices smooth out income between install seasons, which spike after storms.
Most contractors add a markup of 10 to 25 percent on equipment to cover ordering, delivery, storage, warranty handling and risk. Show it as a single line price for the unit rather than your cost plus a markup, unless the contract is cost-plus.
Usually after the final inspection passes and the generator has been started and load tested. Put that condition in your contract so the due date is clear.
It depends on the state and on whether the job is treated as a sale of goods or a real property improvement. Some states tax materials, some tax the whole job, and some do not tax residential installs. Check with your state revenue department or a tax professional.
List the permit fee as its own line, either at cost or with a coordination fee for your time. If the fee is unknown at signing, note that the actual permit cost will be billed.
Do not release the unit or energize the system without the agreed payment. A written payment schedule and a lien notice, where allowed in your state, protect you if payment stalls.
Send a Generator Installation estimate for approval, then turn it into an invoice when the work is done.
Generator Installation estimate template