The first time the power went out after I installed a backup unit at my own place, I barely noticed. The lights flickered for about eight seconds, the furnace clicked back on, and my wife kept watching her show. That eight-second gap is the whole pitch, really. You keep living your life while the neighborhood sits in the dark.
I spent twelve years as a licensed electrician, and a big chunk of that was installing and servicing home backup power. So I’ve seen the good installs and the regrettable ones. This is the honest version of what a permanent backup system is, what it runs, and how to decide if it belongs on your property.
Let’s start with the plain-English basics before we get into numbers.
Key takeaways
- A whole house standby generator wires directly into your home and starts on its own within seconds of an outage.
- Most homes run fine on a 14 kW to 26 kW air-cooled unit; bigger homes with big HVAC may need liquid-cooled.
- Expect $5,000 to $18,000 installed, with the transfer switch, gas line, and pad often costing as much as the generator itself.
- Natural gas means no refueling; propane needs a tank you’ll monitor and top off.
What a whole house standby generator actually is
A whole house standby generator is a permanently installed engine-generator that sits outside your home, usually on a small concrete pad or composite base, roughly the size of a central AC condenser. It’s hardwired to your electrical panel through an automatic transfer switch.
When the utility power drops, a controller senses it, cranks the engine, and flips your house over to generator power. No cords, no gas cans, nobody standing in the rain. When utility power returns, it switches you back and shuts the engine off after a short cooldown.
That’s the key difference from a portable unit. If you’re still weighing the two, I’d read through this beginner’s guide to portable generators for home backup first, because a portable is a very different commitment and a lot cheaper to start.
How the automatic transfer switch keeps you safe
The transfer switch is the brain, and it’s the part homeowners underestimate. It physically isolates your house from the grid before the generator feeds power in.
Why that matters: without it, a running generator can back-feed electricity onto the utility lines. That can kill a lineman working to restore your power. It’s not a rare hypothetical. The Consumer Product Safety Commission has documented these back-feed incidents, and it’s exactly why I’ve never once wired a generator without a proper switch.
Never let anyone connect a generator to your panel with a “suicide cord” or a homemade setup. It can electrocute utility workers and start a fire in your walls. A code-compliant transfer switch is not optional, it’s the law in most jurisdictions.
Sizing it right, without overpaying
Sizing is where I see the most money wasted, in both directions. Buy too small and your generator trips when the AC and the well pump kick on together. Buy too big and you paid for capacity you’ll never touch.
The quick gut-check
Most three-to-four-bedroom homes land comfortably on an air-cooled unit between 18 kW and 24 kW. That covers a furnace, a couple of AC tons, the fridge, well pump, and normal outlets and lights running at once.
On a job last winter, a client insisted on a 26 kW because a salesman scared him. His actual load, measured, peaked around 15 kW. He spent about $2,500 more than he needed to. Measure before you buy.
Ask your installer to do an actual load calculation, not a square-footage guess. A good one will look at your panel, your HVAC nameplate, and whether you have well or septic pumps.
For the full method, walk through how to size a generator for your home and the companion piece on what size standby generator an average home needs. They’ll save you from the oversell.
Air-cooled versus liquid-cooled
Air-cooled units use a fan to keep the engine temperature down, like a big lawnmower. They cover most homes up to about 26 kW and cost less to buy and service.
Liquid-cooled units have a radiator and coolant, like a car engine. They start around 22 kW and go well past 60 kW, and they run cooler and quieter under heavy, sustained loads. Big houses, or homes with three-plus AC tons, usually need one.
| Feature | Air-cooled | Liquid-cooled |
|---|---|---|
| Typical size range | 10–26 kW | 22–60+ kW |
| Installed cost | $5,000–$12,000 | $12,000–$25,000+ |
| Best for | Most homes | Large homes, heavy HVAC |
| Noise under load | Louder | Quieter |
There’s more nuance here than a table can hold, so if you’re on the fence between the two, the deep comparison of air-cooled versus liquid-cooled standby generators is worth ten minutes.
Fuel: natural gas or propane
Almost every standby unit runs on natural gas or liquid propane. If your street has a gas line, natural gas is usually the easy call. You never refuel, and the run time is effectively unlimited as long as the utility keeps the gas flowing.
Propane makes sense when you’re rural or gas isn’t available. The tradeoff is fuel management. A 500-gallon tank running a 22 kW unit at half load lasts maybe five to seven days, so during a long outage you’ll be watching that gauge.
One thing folks forget: propane also has a shelf life advantage over gasoline. It doesn’t go stale in the tank, which is a real headache with portable gas units that sit for a year.
What it really costs to own
Sticker price is only part of the story. Here’s roughly how the money breaks down on a typical air-cooled install.
- Generator unit: $3,000 to $6,500
- Automatic transfer switch: $400 to $1,200
- Gas line and plumbing: $500 to $2,500 depending on distance
- Concrete or composite pad: $200 to $600
- Electrical labor and permits: $1,500 to $4,000
- Annual maintenance: $150 to $400
That’s how a “$4,000 generator” becomes an $11,000 project. Nothing shady about it; the labor and gas work are genuinely most of the job. For a line-by-line look, I’d point you to this full standby generator price breakdown.
Budget for upkeep too. These are engines. They want an oil change roughly once a year or every 100 to 200 run hours, plus a filter and a battery every few years. Skip it and you’ll find out during the exact storm you bought it for.
Is it worth it for your house?
Here’s my honest test. If you lose power more than a couple times a year, or you have something that can’t sit dark, a standby unit earns its keep. A sump pump in a flood-prone basement, a medical device, a home office you can’t lose, a well that’s your only water. Those are the clear yes cases.
If you’re in a stable grid area and lose power once every two years for an hour, a good portable and a couple of extension cords may serve you fine for a fraction of the cost. There’s no shame in that.
Before you sign anything, get two or three quotes, confirm the installer pulls permits, and ask to see a load calculation in writing. Read up on generator safety from a source like Ready.gov’s power outage guidance so you know what you’re actually protecting against. Then make the call that fits your outages and your budget, not the salesman’s commission.
