Every August, the same question starts coming in from Tallahassee homeowners: what size generator do I need before the next storm takes the power out? Atlantic hurricane season hits its climatological midpoint on September 10 — that is not a hunch; it is a date NOAA has tracked for decades — and it lands about five weeks out from the day most people start seriously shopping for backup power.

Then, nine times out of ten, the second sentence is the square footage of the house.

Here’s the honest answer, and it is the one no online sizing calculator will give you: square footage is close to meaningless when sizing a standby generator. A 1,600-square-foot house in Wakulla County on a well, with a 4-ton air conditioner and an electric water heater, needs more generator than a 2,600-square-foot house inside the city limits on natural gas with a smaller unit. Same state, same storm, very different math.

What actually sets the size is your electrical load — specifically, which pieces of equipment have to start and run at the same time, and how much current they pull in the instant they kick on.

Why Square Footage Can’t Answer What Size Generator Do I Need

Square footage is a rough proxy for lighting and outlets. Those are the smallest loads in your house.

The loads that actually size a generator are the motors and the heating elements, and they don’t scale with floor area at all. Two houses of identical size can be 8 kW apart because one has a heat pump with an air handler and the other has a 5-ton compressor and a submersible well pump 200 feet down.

Motors are the whole problem. An electric motor — the compressor in your central air conditioner, the pump in your well, the compressor in your refrigerator — draws dramatically more current in the first fraction of a second than it does once it’s spinning. That inrush is brief, but a generator has to be able to deliver it without stalling or dropping voltage. This is the single most common reason an undersized generator “works” for a week and then can’t start the AC on the hottest afternoon of the outage.

In a North Florida home, that inrush problem is not theoretical. It is August.

What Actually Drives the Size of a Standby Generator

When we do a load calculation on site in Tallahassee, these are the items that move the number:

• Central air conditioning. The biggest single driver in nearly every Florida home, and the one that makes generator sizing here different from generator sizing in Ohio. We need the tonnage, the compressor’s locked-rotor draw, and whether the system has a soft starter — a device that limits the startup surge and can meaningfully change the generator you need.
• A well pump. Common through Wakulla, Gadsden, and Jefferson counties and out past the city limits in Leon. A submersible pump is another hard-starting motor, and if you’re on a well, no generator means no water — not just no lights.
• Electric water heater, range, and dryer. These are large resistive loads. If they’re electric rather than gas, they change the calculation substantially. If they’re gas, they barely register.
• Refrigerator and freezer. Small in running watts, but they’re the loads people actually care about at hour 40 of an outage, and many Big Bend households run a second freezer in the garage.
• Well or pool equipment. Pool pumps are motors too, and they’re easy to forget until they’re on the list.
• The circuits you’d be miserable without. One bathroom, the kitchen, the router and modem, a home office, a medical device, a window unit in the bedroom.

And one question that matters more than any single item on that list: does all of it need to run at the same time?

Often it doesn’t. Load management — automatic controls that briefly shed non-essential circuits when the generator is near capacity — can let a smaller unit cover a larger house. That’s a design decision, and it belongs in a conversation with an electrician, not in a chart.

Whole House Generator Sizing: The Three Levels of Backup Power

Most homeowners come in thinking there are two options, on or off. There are really three, and picking the right tier is the decision that drives everything else.

Essentials only. The generator covers a selected group of circuits — lights, refrigerator, a few outlets, the router, one bathroom, maybe a window unit. Your central air is not on it. This is real backup power; it’s the least expensive tier, and for some households it’s genuinely the right call. Be honest with yourself about August, though: a house in Tallahassee without air conditioning in late summer gets uncomfortable fast.

Most of the house. Everything above, plus one central air-conditioning system and the well pump. This is where a large share of North Florida homes land, and for good reason — it’s the tier where an outage stops being an emergency and becomes an inconvenience.

Whole house. Every circuit in the panel, running the way it runs on a normal Tuesday. This is what most people picture when they say whole-home generator. Multiple HVAC systems, electric water heater, range, dryer, pool equipment, shop. Larger homes and heavier electrical demand push you here, and above a certain point the unit shifts from an air-cooled generator to a liquid-cooled one.

Where the size lands, roughly, once the load calculation is done:

• 10–14 kW — essential circuits: lights, refrigerator, outlets, and a few selected appliances.
• 18–22 kW — many average-size homes with one central air-conditioning system.
• 24–28 kW — larger homes, multiple HVAC systems, electric water heaters, pool equipment, or otherwise heavier demand.

Treat those as brackets to evaluate, not as an answer. For a typical Florida home with a single central HVAC system, 22 kW is often a reasonable place to begin the conversation — but it should never be selected without someone looking at your panel and your equipment.

The Fuel Detail Almost Nobody Mentions

Here is a wrinkle that surprises people, and it’s one of the reasons a chart can’t size your generator: most standby generators are rated differently on natural gas than on propane.

Natural gas has lower energy density, so the same machine typically produces somewhat less output on natural gas than on LP. On current manufacturer spec sheets, the top-end air-cooled units from both Generac and Kohler are rated at 26 kW on propane and 24 kW on natural gas — an 8% difference on the same unit, purely from what you’re feeding it.

It isn’t universal. A few models are rated identically on both fuels. But if you’re on natural gas inside the city and the sizing was done off the propane number, you may not have the generator you think you have.

Which fuel you’re on, what pressure your gas service delivers, and how far the line has to run to the pad are all part of the design — not afterthoughts.

Bigger Isn’t Automatically Better

There’s a temptation to solve the whole problem by buying the biggest unit available. It’s the wrong instinct.

Oversizing costs money you didn’t need to spend — on the unit, on the gas line, on the pad, on the fuel it burns during every exercise cycle for the next fifteen years. It also means running a large engine at a low load fraction most of the time, which is not what the machine is designed around.

Undersizing is worse. An undersized generator either overloads and shuts down, or it can’t start the AC compressor, and you find out about it during the outage rather than during the quote. Overload is one of the five most common reasons a generator fails when you need it, and it traces straight back to how the unit was sized.

The right answer is neither the biggest nor the cheapest. It’s the one that matches your actual load, with sensible headroom.

How Whole House Generator Sizing Actually Gets Done On Site

Both major manufacturers recommend a professional site survey and load assessment before selecting a unit, and there’s a reason for that. When we do one in Tallahassee, we’re looking at:

• HVAC size and startup amperage, and whether a soft starter is present or worth adding
• Which appliances are electric and which are gas — water heater, range, dryer
• Well pump or pool pump, and their starting characteristics
• Your existing panel — service size, available space, condition, and whether a transfer switch can be integrated cleanly
• Whether everything truly has to run simultaneously, or whether load management can do some of the work
• Your fuel — natural gas or propane — and the generator’s rating on that specific fuel

That takes a technician standing at your panel with the meter can open. It does not take a form on a website.

We’ll tell you if a smaller unit covers what you actually care about. We’ll also tell you if the number you had in your head is going to leave you sitting in the dark with a generator running.

Frequently Asked Questions

What size generator do I need for a 2,000 sq ft home? There isn’t a reliable answer tied to square footage, which is why the question is so hard to answer honestly online. Two 2,000-square-foot homes in Leon County can need very different generators depending on air-conditioning tonnage, whether the water heater and range are electric or gas, and whether the home is on a well. Most homes that size with a single central HVAC system evaluate in the 18–22 kW range, but that’s a starting bracket, not a spec.

Will a whole-house generator run my central air conditioning? A properly sized one will. The AC compressor’s startup surge is usually the greatest single demand the generator has to handle, so it has to be part of the sizing from the beginning — not something added later. If your system has a soft starter, that reduces the surge and can affect which unit you need.

Do I need a bigger generator if I’m on a well? Usually, yes. A submersible well pump is a hard-starting motor, and it’s also non-negotiable: without it you have no running water, no toilets, and no showers. Homes on wells in Wakulla, Gadsden, and Jefferson counties frequently size up a tier compared to a similar home on city water.

Can I just get a smaller generator and run fewer things? Yes — that’s the essentials-only tier, and it’s a legitimate choice. The important part is deciding deliberately which circuits are on it rather than discovering the limits during a four-day outage. Load management can also stretch a smaller unit further than you’d expect by shedding non-essential loads automatically.

Is a generator sizing calculator accurate? Online calculators are useful for getting oriented, and not much more. They don’t know your compressor’s locked-rotor amps, your panel’s condition, your fuel type and pressure, or whether your dryer is gas. Manufacturers themselves recommend an on-site load assessment before a unit is selected.

How long does a whole-house generator run during an outage? A standby generator connected to a natural gas line runs as long as the gas keeps flowing, which in most outages is indefinitely. On propane, runtime depends on tank size and load — which is another reason the load calculation matters. Either way, generators need to be shut down periodically for oil checks on very long runs.

Does the generator size affect the transfer switch? Yes. The automatic transfer switch — the device that senses the outage, disconnects you from the utility, and starts the generator — is matched to the service and to the scope of what’s being backed up. An essentials-only design and a whole-house design use different switch configurations, so the two decisions get made together.

Get the Number From Your Panel, Not From a Chart

The correct size for your home is a specific number, and it exists. It just isn’t on a webpage — it’s the output of a load calculation done at your house, on your equipment, with your fuel.

We’ve been sizing and installing standby generators across the Big Bend long enough to know which houses surprise you. Sometimes it’s the modest ranch with the 5-ton unit and the well. Sometimes it’s the big house that’s mostly gas and needs less than the owner assumed. You find out by looking.

With the peak of hurricane season a few weeks out, the time to find out is now — permitting, gas work, and utility coordination all take longer than the install itself. In the meantime, our outage coverage page keeps the live City of Tallahassee and Talquin outage maps in one place.

📞 GT Electric of Florida — We’ll do the load calculation at your home and tell you the honest size, including if it’s smaller than you expected. Schedule an assessment: (850) 655-0868 | Contact us online

Serving Tallahassee, Leon County, Wakulla, Gadsden, and Jefferson Counties since 1979. Licensed, insured, and locally owned.