Quick answer:** There’s no single number that works for every house. Most homes in our service area land somewhere between **20 kW and 32 kW**, but where you fall in that range depends on your square footage, how many air conditioners you have, and whether your home runs on natural gas or is all-electric. Below is how sizing actually works, and what a free in-home assessment tells you that guesswork can’t.
The Short Answer
Two real examples from actual assessments we’ve run:
Home Profile – Recommended Size – Why
~4,500 sq ft, natural gas, 3 AC units | 27 kW (liquid-cooled) | Sized so all three ACs can restart together after an outage |
~4,000 sq ft, all-electric | 32 kW | Water heater, range, and dryer all draw from the generator too |
These are real recommendations, not a formula you can apply to your own home — a house with the same square footage but a different number of AC units, or different appliances, can need a very different size. The only way to know your actual number is the free in-home assessment covered further down.
Why Square Footage Alone Doesn’t Decide It
Square footage tells you roughly how much your home needs to run day-to-day — but sizing a generator is really about the moment your air conditioners kick back on after the power comes back. When an AC compressor starts up, it briefly pulls several times more power than it does while running normally. Electricians call this **starting surge** (or “inrush”).
*Plain English: if you have two or three AC units and the power comes back with all of them trying to restart at the same time, that momentary spike — not the day-to-day running load — is what determines the smallest generator that won’t stall or shut down.*
That’s why a generator sized “close enough” on paper can still struggle in practice: it’s not about whether it can power your house, it’s about whether it can survive the first few seconds when everything switches back on at once.
One more wrinkle worth knowing: a generator’s advertised size assumes a specific fuel. Most residential units are rated for both natural gas and propane, but many produce noticeably less power on natural gas than their propane rating suggests — the gap varies by brand and model. It’s one more reason the number on a spec sheet isn’t the same as the number that matters for your home; your technician confirms the real output for your specific unit and fuel type during the assessment.
Natural Gas Homes vs. All-Electric Homes
If your home runs on natural gas, your generator only needs to cover things like AC, lighting, and receptacles — your water heater, range, and dryer are already running on gas and don’t touch the generator at all. If your home is all-electric, all of that load shifts onto the generator too, which usually means a meaningfully bigger unit than a gas home of the same size.
> We’ve seen this catch homeowners off guard: one all-electric, roughly 4,000 sq ft home came in assuming a 22 kW generator would be enough. Once the full load — including the electric water heater, range, and dryer — was calculated, the actual recommendation came back at 32 kW. Self-estimates for all-electric homes tend to run low for exactly this reason.
If you’re not sure whether your home counts as “all-electric” for sizing purposes, mention your water heater, range, and dryer fuel types when you schedule your assessment.
What the Free In-Home Assessment Actually Calculates
Rather than a sq-ft-per-kW rule of thumb, we run a formal load calculation on-site and put it in writing as the first page of your estimate. It combines:
– Square footage — the baseline size and layout of your home.
– Number and tonnage of your AC units — the biggest driver of starting-surge load, and the main reason two similar-sized homes can need different generators. AC units that haven’t been serviced in the last year can also draw more amperage than they should, which throws off the numbers — if yours is overdue for a tune-up, we can refer you to our sister company, Parrain’s Heating & Air Conditioning, for a quote.
– Lighting and receptacle load — everything else plugged in or wired throughout the house.
You’ll get a specific kW recommendation in writing, not a range — ask your technician to walk you through it so you can see exactly what it does and doesn’t include before you decide on a unit.
Can I Choose a Smaller Generator Than Recommended?
Sometimes — but “smaller” only works safely if something else changes to make up the difference. A few real options, roughly in order of what we’d recommend trying first:
– LED retrofits. Switching your home’s lighting to LED lowers your overall electrical load, which can be enough on its own to bring your recommended size down a notch. No downside, no equipment risk.
– Load shedding. A management module can stagger or briefly delay your AC units from restarting at the exact same moment, cutting the peak surge a smaller generator has to survive — for example, turning a roughly 30 kW peak into something closer to 24 kW.
– Selected-circuits units. Instead of powering the whole house, a smaller unit (commonly 14–18 kW) can be wired to a handful of priority circuits — usually one AC, refrigeration, and key outlets — rather than everything.
– Soft starts. A soft-start device smooths out an individual AC compressor’s startup draw, often letting a smaller generator handle multiple units. Installs typically run **$800–$1,200 per unit**.
> Important: soft starts need to be matched to what’s already on your AC. If your unit already has a different type of start-assist device, adding a soft start without checking first can cause equipment damage and create a warranty issue with your AC’s manufacturer — ask your technician to confirm compatibility before installing one, not just recommend it. Please also let us know if another company already services your AC under a maintenance plan, so we can coordinate with them rather than risk your existing warranty. If you don’t have a maintenance plan in place, we can refer you to our sister company, Parrain’s Heating & Air Conditioning — Craig’s customers get a discount there.
Whichever route you choose, get the tradeoff in writing: what the smaller unit will and won’t power if every AC tries to start at once. That’s the scenario sizing is built around, and it’s worth seeing on paper before you decide.
Quick Questions About Sizing
Why does a bigger generator cost so much more?
Size is one of several things that drive price, alongside site work, gas line sizing, and electrical panel needs. See *”How Much Does a Whole-Home Generator Cost in Louisiana?”* for a full breakdown.
Does a bigger generator mean more noise, or a different spot in my yard?
Size plays a role, but placement is mostly driven by local setback rules and clearance from windows and doors, not just kW. We’ll cover this in detail in an upcoming article on generator placement and noise.
Can I resize my generator later if my needs change?
In some cases — adding solar, a pool, an EV charger, or converting appliances to electric down the road can increase your load enough to be worth revisiting. Talk to your Craig’s Electrical project coordinator about a follow-up assessment if your household’s power needs change after installation.
*Have a question about your specific home? Reach out to your Craig’s Electrical project coordinator anytime.*