A whole house standby generator costs roughly $9,000 to $20,000 fully installed for a typical 14 to 26 kilowatt system. Most 22 kilowatt installs, the size that covers a larger home including central air conditioning, land somewhere between $10,000 and $14,000. Essential-circuit systems in the 10 to 14 kilowatt range run about $7,000 to $12,000, and large or complicated projects can exceed $25,000.
I want to be direct about that number, because it is the part most homeowners get wrong. The generator itself is usually the smaller half of the bill. A 22 kilowatt unit runs around $5,000 to $7,000, and everything required to make it work adds several thousand more on top.
Here is how sizing actually works, what the full project costs, and why this is a decision worth making during design rather than three years after you move in.
What a whole house standby generator is, and is not
A standby generator is permanently installed on a pad outside the house, hard-wired into your electrical system through a transfer switch, and fueled by natural gas or propane. It starts on its own within seconds of an outage. You do not roll it out of the garage, you do not run extension cords, and you do not refuel it in the dark.
That permanence is what drives both the cost and the code requirements, and it is why standby pricing looks nothing like the numbers you see attached to portable units.
Sizing is a load calculation, not a square footage rule
You will find plenty of charts online that match generator size to house size. They are a rough orientation at best. What actually determines the size you need is your calculated electrical load, meaning how much power the systems you want backed up will draw at the same time. Under the National Electrical Code, the calculated load determined by Article 220 must not exceed the generator's output rating. An electrician or your installing dealer runs that calculation from your panel and your list of backed-up circuits.
For general orientation, here is roughly where the sizes land:
- 8 to 10 kilowatts covers the essentials only, typically heat, refrigeration, a well pump, and a handful of outlets
- 14 kilowatts is the most common size, and generally runs a small to medium home including one central air conditioning unit
- 22 to 24 kilowatts covers a larger home with central air conditioning and heavy loads, and typically handles a home up to roughly 2,500 square feet running central air, an electric range, and an electric dryer simultaneously
- 26 kilowatts and above, often liquid-cooled, serves large homes, dual air conditioning systems, or households charging electric vehicles
Two homes of identical square footage can need very different units. A house with a well pump, an electric range, and two air conditioning units draws far more than the same size house on rural water with gas appliances. This is exactly why sizing off the plan, with the actual specified equipment in front of you, produces a better answer than a chart.
There is also a way to size down honestly. A load management module sheds non-critical circuits automatically when demand spikes, which can let a smaller generator cover more of the house. Ask your installer whether that changes the size you need, because it sometimes changes the price meaningfully.
Where the money actually goes
The unit is one line item. These are the others.
Automatic transfer switch. Roughly $500 to $1,500 for a residential system. This is the device that disconnects the house from the utility and connects it to the generator.
Electrical work. About $1,500 to $3,000 for conductors, conduit, and panel connections.
Gas line connection. Roughly $500 to $1,500, more if the run is long or requires trenching.
Concrete or composite pad. About $300 to $600 for a standard residential pad.
Permits. Generally $200 to $500. Most installs need more than one, since the electrical work and the fuel line are usually inspected separately.
Labor. Frequently $4,000 to $7,000 all in, since a complete install involves a licensed electrician and a gas fitter, plus the load assessment, startup, and inspections.
Panel upgrade. If your service is 100 amp, an upgrade to 200 amp is a common addition that catches people by surprise.
Maintenance. Budget $200 to $400 per year for professional servicing. A well-maintained standby unit generally lasts 15 to 30 years.
Operating cost. On natural gas, expect roughly $3 to $5 per hour of runtime.
This is also why two bids on the same generator can differ by several thousand dollars. One contractor may include gas meter coordination and permits while another leaves them as owner responsibility. Ask each bidder to itemize.
The code requirement you cannot design around
A permanently installed residential generator falls under NEC Article 702, which covers optional standby systems. Section 702.5 requires transfer equipment that prevents the generator and the utility from energizing the wiring at the same time. This is not a formality. Backfeeding sends generator power through the transformer and onto distribution lines at thousands of volts, where utility crews expect dead wire.
Article 702 permits either manual or automatic transfer equipment, since optional standby loads are not life safety loads. Automatic is the standard choice for a permanent whole house install, because the entire value of the system is that it works when nobody is home to throw a switch.
Why this belongs in the design conversation
A generator added after move-in has to work around whatever panel, gas line, and exterior space already exist. That is where the expensive surprises come from.
A generator planned during design gets three things right from the start. The pad location is chosen for both function and appearance, which matters because the unit sits outside and has clearance requirements around it. The gas line is sized for the generator's demand alongside everything else on the system rather than being spliced into later. And the electrical panel is specified with enough capacity to carry the transfer switch, which avoids a service upgrade that can add thousands on its own.
This matters more on rural property. Distance between the house, the panel, the generator pad, and any propane tank drives both cost and code compliance, and outages in those areas tend to run longer. If you are already planning a propane tank for cooking or heating, sizing that tank with the generator's fuel demand included avoids running two separate fuel projects instead of one.
Questions to ask before you commit
- What is my calculated electrical load, and which circuits are we backing up?
- Would a load management module let me install a smaller unit?
- Where does the pad go, and how far is it from the panel and the gas source?
- Does my service need an upgrade to support the transfer switch?
- What does this bid include, line by line, and what is left to me?
If you are planning a new build and want the pad, the gas line, and the panel capacity accounted for before construction starts rather than retrofitted afterward, book a design consultation and we can build it into the plan from the beginning.
Frequently asked questions
How much does a whole house generator cost installed?
Roughly $9,000 to $20,000 for a typical 14 to 26 kilowatt standby system, including the unit, transfer switch, pad, gas hookup, electrical labor, and permits. Most 22 kilowatt installs land between $10,000 and $14,000. Smaller essential-circuit systems run about $7,000 to $12,000.
What size generator do I need for a 3,000 square foot house?
Most homes that size with central air conditioning land in the 22 to 26 kilowatt range, but square footage does not decide it. The calculated electrical load does. A 3,000 square foot home on gas appliances may need less than a 2,200 square foot home with a well pump and two air conditioning units.
Do I need a transfer switch?
Yes. NEC 702.5 requires transfer equipment that prevents the generator and the utility from being connected simultaneously, which protects utility crews from backfeed. Article 702 allows manual or automatic equipment, though automatic is standard for a permanent whole house install. Budget roughly $500 to $1,500 for a residential automatic switch.
How much does generator maintenance cost per year?
Plan on $200 to $400 annually for professional servicing. Scheduling it before summer and before winter is the usual advice, since those are the seasons that test the system.
Should I plan for a generator during design or add it later?
During design, if you have the choice. Pad placement, gas line sizing, and panel capacity are inexpensive to specify on paper and expensive to correct once the house is standing.
