Start with the question everyone actually asks
“What size generator do I need?” is the first thing most Panhandle homeowners want answered, and it is the one where guessing costs the most. Pick a unit that is too small and it trips the first time your air handler kicks on during a July outage. Oversize it and you have paid for capacity that never gets used. The honest answer is that your home’s size is measured in kilowatts of demand, not square feet, and on the Emerald Coast one load drives the whole calculation more than any other: your air conditioning. This guide walks the logic plainly so you understand the number before an installer ever quotes you. The resource here connects you with one vetted, licensed local installer; the on-site load calculation is theirs to run.
What size generator to run a whole house
Whole-house standby generators are rated in kilowatts (kW), and that rating is what “size” means. For a typical single-family Panhandle home, whole-house coverage usually lands somewhere between 18 kW and 26 kW of air-cooled capacity. Larger homes, multiple AC systems, a pool, or a well pump can push the requirement to 27 kW and up, into the liquid-cooled tier. The kW rating tells you how much load the unit can carry at once, and the goal is to match it either to your entire house or to the specific circuits you most want kept alive.
Sizing by home square footage (as a rough starting point)
Square-footage rules of thumb are everywhere online, and they are fine for a first sanity check and nothing more. As loose brackets for Panhandle homes:
- Under ~1,500 sq ft, one AC system: roughly 14 to 18 kW is often enough, especially with managed circuits.
- ~1,500 to 3,000 sq ft, one or two AC systems: frequently 20 to 26 kW air-cooled for whole-home coverage.
- Over ~3,000 sq ft, multiple compressors, pool, well: commonly 27 kW and up, often liquid-cooled.
Treat these as a way to know whether you are shopping for a small, medium, or large unit, not as a spec. Two houses of identical square footage can draw wildly different power depending on their appliances, which is why the real number comes from a load calculation, not a chart.
kW by appliance: adding up what your home draws
A genuine sizing exercise adds up the running watts of your major loads, then accounts for startup surge on anything with a motor. Rough running figures help you see where the demand sits:
- Central AC (3 ton): about 4,000 to 5,000 running watts, with a much larger startup spike
- Electric water heater: about 4,500 watts
- Electric range or oven: about 3,000 watts
- Electric dryer: about 5,000 to 5,400 watts
- Well pump (1 HP): about 2,000 running watts, roughly double at startup
- Refrigerator or freezer: about 700 watts running
- Pool pump: about 2,000 watts running
- Lights, outlets, Wi-Fi, and small electronics: often 2,000 to 3,000 watts combined
Add the running loads you want live at once, then add the single largest startup surge on top. That surge-plus-running total, not the plain sum, is the number the generator has to satisfy. Our generator sizing calculator does this arithmetic for you as a planning aid.
The deciding factor: AC startup surge
This is the part unique to hot climates, and where DIY sizing usually breaks. An air conditioner does not draw a steady amount. The instant the compressor starts, it pulls a brief inrush that can spike to several times its running draw for a split second. The generator has to absorb that surge without sagging, or it trips offline and the AC never comes on.
On the Emerald Coast, where AC runs hard from spring into fall and many homes carry two systems, that startup surge, not the steady-state load, is frequently the single largest demand the generator ever sees. Size only to the running watts and you have bought a unit that fails exactly when you need cooling most, during a humid post-storm outage. A good installer accounts for this directly. Soft-start devices on the compressors can tame the spike and let a smaller generator do the job; whether that trade is worth it for your home is exactly what a real load calculation reveals.
Whole-home vs. managed (load-shedding) sizing
Two broad strategies exist, and the choice changes the size you buy.
Whole-home backup sizes the generator to run essentially everything at once, both AC systems, the full kitchen, every outlet. An outage feels like nothing happened, at the cost of a bigger, pricier unit.
Managed (load-shedding) backup pairs a smaller generator with a smart panel that prioritizes. Instead of powering everything simultaneously, it juggles the big loads, briefly pausing one AC compressor while the oven runs, then rebalancing. You keep the whole house functional without paying for peak-everything capacity. For many two-story homes around Destin and Fort Walton Beach with two AC zones, load management is the sweet spot. The transfer switch guide covers how the smart panel handles this.
Standby generator sizing and fuel
The same generator does not produce the same output on every fuel. Standby units here run on natural gas or propane, and they generally make somewhat less usable power on natural gas than on propane, a de-rating of a few percent that varies by model. So “a 22 kW generator” is not a fixed promise; delivered capacity depends on what you feed it. If your home sits on the edge between two sizes, fuel choice can tip the decision, which is why standby generator sizing and fuel get settled together. Work through our natural gas vs. propane guide alongside this one, and factor in which fuel even reaches your address.
Why a rule of thumb is not enough
Square-footage shortcuts ignore the variables that actually move the number:
- How many AC tons, and whether there are one or two systems
- Electric vs. gas water heating, cooking, and clothes drying
- A private well pump (common on rural Crestview-area properties) versus city water
- Pool pumps, EV chargers, workshop equipment
- Whether you want true whole-home backup or a managed setup
A genuine load calculation adds up your real appliances and circuits, applies the right surge factors, and accounts for fuel de-rating. That is the difference between a generator that carries your home through a week of no power and one that nuisance-trips on a hot afternoon.
Estimate, then verify
To get in the ballpark before talking to anyone, run our generator sizing calculator. It is a planning aid for understanding roughly where your home falls and what to ask, not a final spec and not a quote. The real number comes from an on-site evaluation, because nobody can see your panel, your AC tonnage, or your well pump through a web form. If you are still deciding whether you need standby power at all, back up to our guide on whether you need a standby generator. When you want a properly sized recommendation for your specific home, the vetted local installer we partner with runs the on-site calculation and stands behind the result. Comparing brands too? See Generac vs. Kohler vs. Cummins and the best whole-house generator guide.