What Size Backup Generator Do I Need for a Texas Home?

The most common way to ask this is "what size generator do I need for a 2,000 square foot house." It's the wrong question, and the answer you get from square footage alone will be wrong often enough to matter.

Two houses on the same street, same size, can need generators two sizes apart. One has gas heat, a gas water heater, and one AC unit. The other is all-electric with two AC units. The second house needs materially more generator than the first.

Here's how sizing actually works, what the numbers look like for a typical North Texas home, and why the AC is the part that decides it.

Sizing Is About Load, Not Square Feet

A generator has to do two things: carry the total running load of everything on at once, and survive the surge when a big motor fires up.

That second part is where sizing goes wrong. An air conditioner compressor draws two to three times its running wattage for the first second or two it engages. If your generator can carry the running load but can't absorb the surge, the AC won't come on, or the generator will trip and shut down. In August in Texas, that's a failed install.

So the calculation is: add up running watts for everything you want backed up, then add the largest single surge on top of that, then add headroom.

Where the Watts Go in a Texas Home

These are typical figures. Your actual equipment will vary, which is why the assessment matters.

Look at that table and one thing jumps out: the air conditioning dwarfs everything else. A single 5-ton unit can surge to 16,000 watts. That is most of a 22kW generator's capacity for the moment it engages.

Everything else in a normal house – lights, internet, TVs, fans, phone chargers, the fridge, garage door, security system – adds up to a few thousand watts combined. The AC is the sizing decision. Everything else is rounding.

Typical Sizing by Home Size

With that in mind, here's the general shape of it for North Texas homes. Treat these as reference bands, not quotes.

Gas appliances are why the first row is so much lower than the third. A gas furnace only needs power for the blower and controls – a few hundred watts. An electric furnace or heat strips can pull 10,000 to 20,000 watts on their own. Same for water heating: a gas water heater needs almost nothing electrically, an electric one needs 4,500 watts. If your house is all-electric, you need meaningfully more generator, full stop.

The Two-AC Problem in Newer Collin County Homes

Most newer construction in Frisco, Prosper, Celina, and north McKinney runs two AC systems – one for downstairs, one for upstairs. Both can call for cooling at the same time on a July afternoon.

Two 4-ton units running together is roughly 7,000 to 9,800 running watts. If both compressors engage at the same moment, the combined surge can exceed 20,000 watts. Sizing for that worst case pushes you to a large unit fast.

There are two ways to handle it:

Size up. Buy enough generator to handle both units engaging simultaneously with no coordination. Simple, reliable, and the most expensive path.

Manage the load. A load management module sequences the two AC units so they never engage at the same instant, and sheds non-essential heavy loads – dryer, water heater, oven – when total demand approaches capacity. You never notice it happening. A soft starter on the compressor reduces surge draw at the moment of engagement, which does the same job from a different direction. Soft starters run a few hundred dollars each.

Load management often lets a 22kW unit cover a home that would otherwise need 26kW or more. Since a two-size jump in generator costs several thousand dollars, this is usually the better economics. It's also the piece most online sizing calculators ignore entirely, which is why they push you toward a bigger unit than you need.

Whole Home vs Managed Whole Home vs Essentials

Three different products get sold under similar-sounding names.

Whole home, unmanaged. Every circuit, everything at once, no coordination needed. Largest generator, highest cost, simplest operation.

Managed whole home. Every circuit is backed up, but load management sequences the heavy hitters so peak demand stays under capacity. Functionally identical from inside the house – you run everything, you just can't run the oven, the dryer, and both AC units at the exact same second. Smaller generator, lower cost. This is what most Collin County homes should be buying.

Essentials only. A subpanel with selected circuits: kitchen, one AC zone, internet, a few outlets, garage door. Cheapest by a lot. Fine if you're covering a short outage and can live with half the house dark. Understand that's what you're buying, because it is frequently sold as "whole house."

The fastest way to tell which one you've been quoted: ask how many circuits the transfer switch covers. A 16-circuit switch is not a whole-home setup regardless of what the proposal says.

Why Undersizing Is the Most Expensive Mistake

Oversizing costs you money once, at purchase. Undersizing costs you every time the power goes out.

An undersized generator that can't carry the load will nuisance-trip, shut down under demand, or simply fail to bring the AC on. You paid five figures for a machine that runs your lights while the house heats up. Worse, running a generator at or near its ceiling constantly is hard on the engine and shortens its life.

The other direction has a cost too. A significantly oversized generator runs under light load most of the time, which is inefficient and, on diesel units, causes its own problems. On natural gas residential units it's mostly just wasted money.

Correct sizing – with load management where it makes sense – is the whole job.

What We Measure at the Assessment

The load calculation takes about an hour and costs nothing. We look at:

• Your service panel: amperage, available spaces, condition, and every breaker in it
• AC tonnage and count, plus the age and type of each condenser
• Gas versus electric on the furnace, water heater, range, and dryer
• Pool equipment, EV charger, well pump, shop or garage subpanel, anything on a dedicated circuit
• What you actually want running during an outage, which is a conversation, not an assumption
• Generator placement, clearances, and the distance to both the gas meter and the panel

Then you get one recommended size, an explanation of why, and a fixed written price. If load management gets you to a smaller unit, we'll tell you that, because the alternative is selling you a generator you didn't need.

For what the finished number typically looks like, see our Collin County whole house generator cost breakdown.

FAQ: Backup Generator Sizing

What size generator do I need for a 2,000 sq ft house? For a 2,000 square foot North Texas home with one AC unit and gas heat and water, 18 to 22kW covers the whole house comfortably. Make that house all-electric or give it two AC units and you're looking at 22 to 24kW. Square footage sets the neighborhood; your AC and your gas appliances set the actual number.

How many kW do I need to run my whole house? Most Collin County homes land between 18kW and 26kW for true whole-home coverage. The spread inside that range is driven almost entirely by air conditioning tonnage, the number of AC units, and how much of the house runs on electricity rather than gas.

Can a 22kW generator run a whole house? For a lot of homes, yes – including many with two AC units, if load management is part of the design. For a large all-electric home with two big AC systems and no load management, 22kW may fall short. The load calculation answers this specifically, and it's not a question worth guessing at.

Will a backup generator run my air conditioner? A properly sized standby generator will, including the surge when the compressor engages. This is exactly what portable generators fail at – they can carry running load but rarely handle AC surge, which is why people with portables sit in the heat with the lights on.

Do I need a bigger generator for two AC units? Bigger or smarter. Two units can surge past 20,000 watts if they engage together, so you either size for that peak or use load management and soft starters to make sure it never happens. The second approach is usually thousands of dollars cheaper.

How loud is a home standby generator? Most residential units run in the 65 to 68 decibel range at about 23 feet, roughly a normal conversation or a window AC unit. Portable generators run 70 to 80 decibels because the engine is out in the open instead of inside an insulated enclosure.

How long does a home standby generator last? Standby units are rated in the range of 1,500 to 3,000 running hours. Because a residential unit only runs during outages and weekly self-tests, that translates to decades of service with annual maintenance.

Get Your Load Calculated for Free

Guessing at generator size is how people end up with a machine that can't run their AC. We'll do the math on your actual house – your panel, your AC tonnage, your appliances – and give you the right size and a fixed price in writing.

Book your free in-home load assessment. It takes about an hour and costs nothing.

Questions? Call (945) 231-3781