Adding a Generator to New Construction

A standby generator for new construction is one of the cheapest luxury upgrades you can buy — not because the generator is cheaper, but because everything around it is. The concrete is already being poured. The walls are open. The gas line is already being run. The electrician is already on site. Planning backup power before the drywall goes up typically saves thousands of dollars in labor alone, and it produces a cleaner, quieter, better-placed installation than any retrofit can.

This guide covers what generator “rough-in” actually means, the four decisions to lock in before framing closes, how to size for a house whose loads do not exist yet, builder and trade coordination, and the 2026 cost picture — rough-in now versus retrofit later. Costs are 2026 US market ranges; get itemized local quotes.

What “rough-in” actually buys you

Rough-in is the construction-phase version of an installation: everything that is cheap to do with open walls and open ground, done now, so the generator itself can drop in later (or now) with minimal labor. For a standby generator, rough-in typically means four things: a conduit or sleeve run from the electrical panel location to the planned generator pad; the pad itself, poured with the foundation or flatwork; a gas stub — natural gas tee and run, or the propane line route with trench left open — sized for the generator’s demand; and a planned location for the automatic transfer switch (ATS), usually adjacent to the meter or main panel.

The savings are almost entirely labor. Retrofitting a generator means trenching through finished landscaping, fishing conduit through closed walls, coring through foundations, and coordinating trades around your schedule and your furniture. Rough-in means the electrician stubs a conduit in an afternoon and the gas plumber sizes the line while they are already sizing the house. Industry experience consistently shows the labor premium of a retrofit at several thousand dollars over a roughed-in job — money that buys nothing but the privilege of doing the same work later.

Rough-in does not commit you to buying the generator today. That is the point: you can spend a fraction of the project cost during construction to preserve the option of a clean, cheap installation later. Buyers who are unsure whether they want backup power yet should still rough it in — it is the cheapest insurance against a future retrofit.

The four rough-in decisions to lock in before framing closes

1. Generator location and pad. Decide where the unit will sit before the site plan is final. Standby generators need code-minimum clearances — 5 feet from openings like windows and doors, 5 feet from combustible walls, 3 feet front and ends, 5 feet overhead, exhaust facing away from the home — with your local authority having jurisdiction (AHJ) and the manufacturer’s manual as the final word. Pour the pad with the foundation work: a level concrete pad sized to the unit (commonly 3-by-6 feet for air-cooled units) costs roughly $300 to $500 as part of flatwork and an order of magnitude more as a standalone pour later. Pick a spot that keeps exhaust away from the house, is serviceable (a tech needs access all around it), and does not fight your landscaping plan.

2. Conduit from panel to pad. Run an empty conduit — or the actual conductors, if you are installing the generator now — from the main panel or meter location to the pad before backfill and hardscape. Oversize the conduit a step beyond what today’s generator needs; the cost difference is trivial and it future-proofs for a larger unit, a second ATS, or a battery system later. Document the route with photos before it is buried — future you, and any future electrician, will be grateful.

3. Gas sizing. This is the decision most often botched. A standby generator is a huge gas load — a 22 kW-class unit at full tilt draws far more than the furnace and water heater combined — and the gas line, meter, and regulator must be sized for the whole house plus the generator. Tell the gas plumber and the gas utility about the generator before the meter is set: meter upgrades after the fact are slow and expensive. If you are on propane, plan the tank location and the line route now, and size the tank against the generator’s consumption — roughly 2.1 gallons per hour at half load to 3.6 at full load for a 22 kW-class unit, per manufacturer-published figures (approximate).

4. Transfer switch placement and panel planning. Decide now whether the ATS will be service-entrance-rated (replacing or sitting beside the meter/main) or a subpanel model feeding selected circuits, and have the electrician lay out the panel accordingly. If you are building with a 200-amp service — standard in new construction — a 200-amp service-entrance ATS is the cleanest whole-home path. Also plan the panel’s physical space: the ATS needs a home on the wall, and the generator’s control wiring needs a route. Planning this with open studs is a conversation; planning it with finished drywall is a change order.

Sizing a standby generator for new construction loads

The honest difficulty of new-construction sizing is that you are sizing for a house nobody lives in. The disciplined approach: size to the designed loads, not today’s. Your builder’s electrical plan shows the HVAC tonnage, the water heater type, the kitchen’s major appliances, and — increasingly decisive — the EV charger rough-ins. An electric heat pump’s auxiliary heat strips, a pool heater, or two EV chargers change the generator’s job completely. List every large load on the plans and have the electrician or generator dealer run a load calculation against them, with the usual 20 to 25 percent headroom.

Where the numbers land in 2026 practice: a modest new home with gas heat and a gas water heater often backs up fully on a 14-to-18 kW unit; an all-electric or large home with heat strips, electric water heating, and EV charging typically needs 22 to 26 kW, sometimes with load-management modules that cycle big loads so a smaller generator serves a bigger house. Load-management modules deserve their own line in the plan — they are cheap during construction (a few hundred dollars installed with open walls) and are the classic answer to the “do I need the 26 or will the 22 do?” question.

One more forward-looking point: rough in for the loads you will add in five years. An EV charger you are not buying yet, a pool, an ADU — the conduit and panel space cost almost nothing now and everything later. The new-construction advantage is not just cheaper labor; it is the only moment you get to design for the future at present prices.

Builder and trade coordination: who does what

Generator projects touch four parties — the builder, the electrician, the gas plumber (or propane supplier), and the generator dealer/installer — and the failure mode is each assuming another handled the gas sizing or the conduit. Get it in writing. A short scope-of-work addendum to the construction contract should name: who pours the pad, who runs and sizes the conduit, who sizes and runs the gas line (and who coordinates the meter with the utility), who supplies and sets the ATS, who pulls the electrical and gas permits, and who commissions and starts the unit.

Timing matters. The conduit and gas sizing conversations happen before the foundation and rough plumbing; the ATS placement is decided at electrical rough-in; the pad is poured with flatwork; final hookup and commissioning happen near the end of construction, after the meter is set. If your builder has never coordinated a generator, consider having the generator dealer do a pre-drywall site walk with the electrician — one hour of coordination prevents the classic discoveries, like a finished wall where the ATS was supposed to mount or a gas meter sized for the house without the generator.

If you are buying a spec or production home rather than a custom build, ask the builder’s sales office whether a generator rough-in package exists or can be added as an option. Many production builders will add conduit, pad, and gas sizing as a line-item upgrade if asked during the options phase — and almost none will volunteer it.

The cost picture: rough-in now vs. retrofit later

Line item	Rough-in during construction (2026 ranges)	Retrofit later (2026 ranges)
Conduit, panel to pad	$200–$600	$1,000–$3,000 (trenching, fishing, repair)
Concrete pad	$300–$500 with flatwork	$800–$1,500 standalone
Gas line sizing + run	$500–$1,200 marginal	$1,500–$3,000+ (meter upgrade, rerun)
ATS mounting + wiring	Part of electrical rough-in	$1,500–$4,000
Standby unit, 14–22 kW, installed all-in	$8,000–$16,000	$8,000–$16,000 (plus the retrofit premiums above)

Costs are 2026 US market ranges; get itemized local quotes. The pattern is consistent: rough-in captures a few thousand dollars of savings, and — just as valuable — produces the clean installation with the sensible placement that a retrofit rarely achieves. If you install the generator during construction, the whole project typically lands at the lower end of the all-in range because every trade is already mobilized.

Also budget the ongoing costs honestly with the builder: annual professional maintenance (oil, filters, plugs, battery, transfer-switch test), fuel, and the exercise cycle’s trivial fuel use. And note the policy reality: there is no federal clean-energy tax credit for residential standby generators in 2026 — budget the project on its merits, not on incentives that do not exist.

Permits, inspections, and the finished-house checklist

New construction simplifies permits — the generator’s electrical, mechanical, and gas permits ride along with the house’s permit package — but it does not eliminate them. Confirm with your builder that the generator scope is in the permit drawings: the AHJ wants to see the ATS location, the gas line sizing, and the pad placement on the plans. HOA architectural review applies in many communities and is easiest to clear before the house is finished; get written approval early.

Before final walkthrough, commission the system properly: witness a full automatic transfer test (utility disconnect simulation), confirm every intended circuit transfers, verify the exercise schedule is programmed, and collect the manuals, warranty registration, and the dealer’s maintenance schedule. Photograph the buried conduit route and the gas line path while they are still visible — file those photos with the house documents. Five years from now, when you add the EV charger or the battery, you will open that folder and thank yourself.

Getting quotes: the new-construction conversation

Bring the house plans — electrical, gas, and site — to two or three generator dealers or licensed electricians who do standby work. Ask each one: what size does the load calculation support, where would you place the pad and the ATS, how are you sizing the gas service for the generator, and what does the rough-in-only option cost versus the full install now? The good ones will ask about your five-year loads before you mention them.

Get everything itemized — pad, conduit, gas, ATS, unit, commissioning — and get the trade-coordination responsibilities in the construction contract in writing. Verify licenses with your state board. Done right, the generator rough-in is the quietest money you spend on the house: invisible in the finished home, and the reason a future outage is a non-event.

Frequently asked questions