What Size Generator Do I Need for My Jacksonville Home?

Most Jacksonville homes between 1,800 and 3,500 sq ft are best served by a 20kW or 22kW home standby generator. That's the size we install most often, and for good reason — it's enough capacity to run your AC, kitchen, lights, and most outlets during an outage without paying for power you'll never use.

But here's the honest answer to "what size do I need": square footage doesn't tell us, and any sizing tool that asks only for square footage is giving you a guess at best. The right way to size a home standby generator is through a load calculation that accounts for your actual appliances, your AC tonnage, your panel layout, and which circuits you want running when the grid goes down.

Why square footage is a lie (or at least misleading)

Two homes in Mandarin, both 2,800 sq ft, can have wildly different power needs:

• Home A: Gas heat, gas water heater, gas dryer, gas range, 3-ton AC, single oven. Total surge load around 38 amps.
• Home B: Heat pump, electric water heater, electric dryer, electric range, 5-ton AC, double oven, EV charger. Total surge load around 90+ amps.

Same square footage. Wildly different generator needs. Home A is comfortable on a 16kW unit. Home B needs a 24kW or load-managed 22kW.

Most online "generator sizing calculators" ask for square footage and number of bedrooms and spit out a recommended size. They're guessing. A real load calc takes 20–30 minutes during an on-site quote and gives you a number that's actually correct.

A rough sizing guide (use as a starting point, not a final answer)

If you want a quick mental model before we come out:

| Home profile | Likely size | |---|---| | 1,500–2,000 sq ft, gas-heavy, single 3-ton AC, no pool | 10–14kW | | 2,000–3,000 sq ft, mixed gas/electric, single 4-ton AC | 18–20kW | | 3,000–3,500 sq ft, mostly electric, dual AC | 22–24kW | | 3,500+ sq ft, all-electric, dual AC + EV + pool | 26kW or load-managed |

This gets you in the right ballpark. A real quote refines it.

What a real load calculation actually checks

When we run the numbers on a Jacksonville-area home, we look at:

• AC tonnage and number of compressors. A 5-ton AC compressor pulls a startup surge that can momentarily exceed 80 amps before settling to 25–30 amps running. Your generator needs to absorb that surge without bogging down.
• Well pump or pool pump. Same surge math. Well pumps in Clay County and outlying St. Johns properties especially.
• Electric water heater, range, dryer. Each pulls 30–40 amps when active, but they don't all run simultaneously. A load calc accounts for diversity.
• EV charger, if present. A Level 2 home charger pulls 30–48 amps continuously while charging. We typically recommend load-managing the EV charger off during an outage rather than oversizing the generator just for it.
• Pool equipment. Variable-speed pumps are easier on a generator than single-speed; heaters are AC-resistive loads.
• Office or basement loads. Sump pumps especially in Riverside and lower Mandarin properties.

The 80% rule we always apply

Industry standard: never size a generator so that peak load equals 100% of its continuous output. The unit will run hotter, use more fuel, and respond worse to surges. We size to 80% peak utilization at most — the unit you buy should run your loaded home with comfortable headroom.

A 20kW Generac with a calculated peak load of 18kW is undersized. The same unit with a peak load of 14kW is correctly sized.

Load management: when a smaller unit makes sense

For some Jacksonville homes — especially newer construction with EVs, dual AC, and electric appliances — a 20kW with load management can cover what a 26kW would otherwise be needed for. Load management is a smart transfer switch (or panel module) that automatically sheds non-critical loads when total demand approaches the generator's limit.

Practical example: a 22kW unit with load management can run a Mandarin home with two AC compressors, an electric water heater, a kitchen, and lights — IF it sheds the EV charger and the pool pump during the outage. The homeowner saves $1,500–$2,500 vs. upgrading to a 26kW just to power equipment that doesn't matter during a power outage anyway.

We default to recommending load management on any 22kW+ install where the home's calculated peak is close to the unit's capacity.

Why oversizing is also a mistake

A common reaction: "let's just buy the biggest one to be safe." Oversizing has real costs:

• More expensive to buy — a 26kW costs ~$2,500 more than a 22kW
• More expensive to run — fuel consumption scales with capacity, even at light load
• Worse for the engine — internal combustion generators run best at 50–80% load. A 26kW unit at 30% load (which is where it'd live for a typical home) runs cooler, builds carbon deposits, and shortens life
• Larger physical footprint — Jacksonville setback requirements (5-foot offset from windows, 18 inches from the foundation) become harder to meet with bigger units

The right size is the smallest unit that comfortably covers your real loaded peak with headroom. Bigger isn't safer — it's expensive and sub-optimally tuned.

Floor plan to specific sizes — Jacksonville examples

A few real-pattern examples of installs we've completed in the past year:

• Avondale 1920s, 1,900 sq ft, gas heat + range, 3-ton AC: 14kW Generac. Comfortably covers AC, kitchen, lights, sump pump, and home office.
• Mandarin 2010s, 2,800 sq ft, heat pump, 4-ton AC, electric water heater: 22kW Generac with load management. Covers everything except EV charger.
• Nocatee 2020 build, 3,400 sq ft, dual heat pump (4-ton + 3-ton), all electric: 24kW Generac with load management.
• Ponte Vedra Beach, 4,200 sq ft, dual AC, pool, sauna: 26kW Cummins with full load management.

Your house is probably most like one of those four. The 20-30 minute on-site walk gets us from "probably about 22kW" to "exactly 22kW with load management on the EV circuit." That's the difference between a good install and a generator that runs perfectly for 15 years.

Once you know your size, see actual installed pricing for each kW range and how we recommend between Generac, Cummins, Kohler, and Briggs at that size.