How to Choose a Whole-House Generator

Choose a whole-house generator by measuring what your house actually has to run during an outage, then let that number, your fuel situation, and the quality of the installation pick the machine. The brand on the cover matters far less than the sizing arithmetic, the transfer switch behind it, and whether the fuel line can actually feed it.

That's the whole guide in two sentences. The rest of this post earns it, because every one of those decisions has a wrong version that looks fine at purchase and only shows itself the first time the power drops on a July afternoon.

Start with what must run, not what the brochure says

Generator marketing works in square footage. Panels don't. Two houses of nearly identical size can need machines that differ by half, because one has gas heat and city water while the other runs a heat pump and a well pump. Square footage tells you nothing useful about either one.

So the first step happens with a notepad, not a catalog. Walk your own house and sort every load into two columns.

The must-run column is shorter than most people expect:

• The well pump, if you have one. Outside city water, no electricity means no water: no drinking water, no flushing toilets, no washing hands. For a lot of homes on the rural roads around Rome, Cedartown and Calhoun, this single load is the real reason a generator gets bought. It's also one of the hardest loads to start, which matters later.
• Medical equipment. Oxygen concentrators, CPAP machines, powered lifts, medication that has to stay cold. If anyone in the house depends on one of these, it goes at the top of the list and it changes how seriously you should take everything else in this post.
• Refrigeration. The kitchen fridge, plus the freezer in the garage holding half a season of food. A day without them is an insurance claim in slow motion. The federal food-safety timings for how long a closed refrigerator and freezer actually hold are in how long food lasts in a power outage.
• Heat, in some form. A gas furnace only needs its blower and controls, a modest electrical load. A heat pump or electric furnace is a different animal entirely, and it's the load that most often decides the size of the machine.
• A working sewer, in a few houses. Homes with a basement bathroom below the sewer line usually have an ejector pump. Homes with a sump pump in a wet-year basement know exactly why that pump makes the list.

The comfort column holds everything else: air conditioning, the electric water heater, the dryer, the oven, the shop. None of it is frivolous. Air conditioning in a Georgia August is close to a health item for some people, and we treat it that way when they tell us so. But every item that moves to the must-run column pushes the machine bigger, and the honest exercise is deciding which ones truly belong there.

Why the load calculation beats every rule of thumb

Once the list exists, the sizing question becomes arithmetic, and the arithmetic has one wrinkle that undoes most rules of thumb: motors don't start politely.

A central air conditioner that draws maybe 15 amps while running will pull several times that in the instant its compressor starts. A well pump does the same. That starting surge lasts under a second, but the generator has to survive it without the voltage sagging so far that everything else in the house browns out. An undersized machine doesn't fail gently here. Lights dip, electronics reboot, the generator's breaker trips, and you're standing in the dark next to a running generator, which is its own special frustration.

So a real load calculation adds up the running loads, then asks a harder question: what's the worst-case moment, when the biggest motor starts while everything else is already running? That worst case sizes the machine. The arithmetic itself, running watts against starting watts and where to read the honest figures off your own equipment, is worked through in what size generator do I need.

Here's the part that works in your favor. Modern standby systems support load management, a set of modules or smart breakers that keep the big loads from ganging up. The controller will shed the water heater for the seconds the AC needs to start, or hold the second compressor off until the first is running. Managed well, a house that naively calculates to a very large machine runs comfortably on a noticeably smaller one, because the loads take turns instead of piling on at once. When we run the numbers on an actual panel, the answer often comes in under the figure the brochure suggested. Nobody selling generators by the square foot has any incentive to tell you that.

One caution in the other direction: "whole house" on a spec sheet frequently means "whole house, with management," not "everything at once forever." That's fine, and it's how the equipment is designed to work. Just know it going in, so the first time the water heater pauses during an outage you recognize a feature and not a fault.

Natural gas or propane, in Northwest Georgia terms

A standby generator is the hungriest gas appliance you will ever own, hungrier than the furnace and water heater combined when it's working hard. Fuel is where a lot of installs go quietly wrong, so it deserves plain talk.

If your house already has a natural gas meter, natural gas is usually the answer. The supply is effectively unlimited, which is its great virtue: no tank to watch, no delivery to schedule in the middle of a regional outage. The catch is capacity. The meter and piping were sized for the appliances the house had, not for a generator on top of them, and it's common for the meter to need upsizing and a new, properly sized line run to the pad. That's gas-trade work, it's a normal part of the job, and skipping it is how you get a generator that starts fine on test day and starves the first time it carries real load on a cold morning with the furnace running too. A fuel-starved generator runs rough, sheds load at the worst moment, and wears itself out early. Who you have the meter conversation with depends on where you live. In Trion the town runs its own natural gas system and its own gas department, and it is the utility that answers for the service line and the meter at a Trion property, so that question goes to the town rather than to a statewide company.

If you're beyond the gas lines, and a lot of Northwest Georgia is, propane is the standard answer, and it's a good one. Propane stores indefinitely, the generators run happily on it, and a tank on your property is fuel nobody else's outage can interrupt. The planning question becomes tank size. A machine in the twenty-kilowatt class working hard can burn on the order of two gallons an hour at half load and closer to three and a half working hard, and a tank is only ever filled to about 80 percent of its stamped size. Run that math against a multi-day outage and a small tank shared with the house's other appliances starts looking thin. Have that conversation with your propane supplier before the install, not after the first long outage.

Worth saying for this area specifically: the outages that make people buy generators here are mostly trees and weather, summer thunderstorms and the occasional ice storm that loads every pine limb in the county. Ice events are exactly the scenario where outages run long and propane delivery trucks are busy, which is an argument for the larger tank if you're on the fence.

Air-cooled or liquid-cooled, and where the line falls

Residential standby generators come in two builds. Air-cooled units cool the engine with a fan, the way a mower does, and they cover the range most homes need, topping out in the mid-twenties of kilowatts. Liquid-cooled units carry a radiator and coolant like a car engine, start around where air-cooled ends, and climb from there. They run quieter for their size, tolerate long continuous duty better, and cost a great deal more, with installation to match. Published national ranges for both builds, and for the install stack underneath them, are collected in whole house generator cost.

For most single-family homes around Rome, the honest answer is air-cooled, and the load calculation says so. You cross the line into liquid-cooled territory when the managed load still exceeds what air-cooled machines make: think two or three air conditioning compressors, a well pump, an outbuilding or shop with real equipment, all on one service, or a large home where nothing is allowed to take turns. Some buyers also cross the line for duty-cycle reasons, because they expect week-long runs and want an engine loafing at low speed instead of working near its limit.

What we'd steer you away from is buying liquid-cooled as a flex when the arithmetic doesn't ask for it. You'll pay more up front, more in maintenance, and gain capacity you never touch. The load calculation exists to keep both kinds of mistake off your pad: the undersized machine that stalls on compressor start, and the oversized one that idles away money.

The brand question, answered honestly

Generac dominates this category. That's a market fact, and it's why "Generac" has nearly become the generic word for a standby generator the way Kleenex did for tissue. Kohler, Briggs & Stratton, Cummins and Champion all build competent machines in the same space.

Here's the installer's-chair truth: the machines in this class are more alike than the marketing suggests. An engine, an alternator, a controller, a transfer switch. When we get called to a standby generator that failed in an outage, the cause is rarely the badge on the cover. It's a dead starting battery nobody checked, a gas line that was never sized right, a maintenance schedule that stopped after the first oil change. Installation and upkeep failures outnumber brand failures by a wide margin in what we actually see.

So put your brand energy into two practical questions instead: are parts and qualified service actually available for this unit where you live, and does its controller and load-management ecosystem fit your house? Then let the load calculation and fuel plan drive the rest.

The parts of the job that aren't the generator

The machine is the visible half of the purchase. The install is the half that decides whether it works, and it's worth knowing the pieces before you compare proposals.

The pad and its clearances. The unit sits on a level pad, placed to satisfy its listing: proper distance from windows, doors, vents and the structure itself, so exhaust can't find its way indoors, with room left to service the thing. Getting those distances right on paper costs nothing. Moving a several-hundred-pound machine after the inspector objects costs plenty. There's a comfort angle too: these machines are not quiet, and the far side of the bedroom wall is a better neighbor than directly under the window.

The transfer switch. This is the piece of equipment that senses the outage, starts the generator, moves your house onto it, and reverses all of that when the utility returns. It exists to enforce one rule: your house can never be connected to both sources at once. That rule protects your equipment when utility power comes back, and it protects the line crew working on what they believe is a dead line up the road. It's the reason Georgia treats this work as licensed electrical work at any job size, with no small-job exemption, and honestly it's the part of the job we take most seriously.

The fuel work. Meter upsizing, line sizing, tank setting: gas-trade work, coordinated into the schedule rather than left for you to referee between two contractors.

The permit and inspection. A standby generator install gets permitted and inspected, period. The inspection is not a hoop. It's a second set of trained eyes on the changeover gear and the fuel connection, the two places where a mistake reaches beyond your own property line. Any proposal that's vague about permitting is telling you something, and you should listen.

What owning one actually looks like

A standby generator is not an appliance you install and forget. It's a small engine that spends its life waiting, and waiting is hard on engines.

The machine deals with this by exercising. Once a week, on a schedule you pick, it wakes itself, runs for several minutes without transferring the house, and shuts back down. You'll hear it, and you should want to. That weekly hum is the sound of a starting battery staying proven, oil circulating, and seals staying wet. The day you notice you haven't heard it lately is the day to go look at the controller.

Beyond that, the routine looks like this: oil and filter roughly once a year in a quiet year, and promptly after any long outage, because a hundred hours of continuous running is more work than the engine sees in years of weekly tests. Air filter and spark plugs on the maker's schedule. The starting battery replaced every few years without waiting for it to fail, since a dead battery is the single most common reason a standby generator stays silent when the lights go out. And the humble stuff: keep the clearances clear, don't let shrubs grow into the intake, blow the leaves off before winter.

Whoever installs yours should hand it over properly: walk you through the controller, run a real transfer test under load with you watching, and leave you knowing what the weekly test sounds like and what the fault lights mean. That handover is part of the job, and we treat it that way. What the install itself covers, start to commissioning, is on our generator installation page.

When a whole-house generator is the wrong buy

Sometimes it is, and you deserve to hear that from the people who install them.

If your outages are a few brief events a year, the arithmetic rarely favors a standby system. A portable generator feeding the panel through a properly installed inlet and interlock keeps the essentials running for a fraction of the cost, at the price of walking outside and pulling a cord. The interlock work is still licensed electrical work, and it's still a job we do carefully, but it's a much smaller job. Plenty of households are best served by exactly that, and we'll say so when it's true. The three changeover options, interlock plate against manual switch against automatic switch, are compared side by side in transfer switch vs. interlock kit.

If you're likely to move within a couple of years, if the panel needs work before it can host transfer gear, which is its own project and lives on our panel upgrades and breaker box replacement page, or if nobody in the house depends on power in a way a cooler of ice can't cover, slow down before buying. A standby generator is a long-ownership purchase. It pays you back in well water during ice storms, medical equipment that never blinks, and freezers that stay cold through a week the neighbors will complain about for years. If that describes your house, size it honestly, fuel it properly, and have the changeover done right. That's the entire secret, and none of it is printed on the box.