What size generator for 200-amp service?
Almost every modern house has a 200-amp panel, so this is the most common sizing question we see, and the most common wrong answer is some version of "200 amps means a huge generator." It doesn't. The panel rating tells you what your electrical service can deliver, not what your house actually draws. Sizing still comes from your load list; the panel just decides how the generator connects to it.
What "200-amp service" does and doesn't mean
The arithmetic is simple: 200 amps × 240 volts = 48,000 volt-amps, roughly 48 kW of theoretical capacity. That number is a ceiling for the service equipment, the utility feed, meter, and main breaker, not a measurement of your home. In practice, a house almost never runs everything at once: the dryer cycles, the oven preheats and rests, the AC compressor is off half the hour, and the well pump runs in bursts. If you add up the ratings on every breaker in the panel you'll get several hundred amps, which is fine, because they were never meant to sum.
So "200-amp service" does not mean you need a 48 kW generator, a size that barely exists in residential air-cooled standby. It also doesn't mean a 200-amp transfer switch makes your generator a 200-amp machine: a service-rated switch is built to carry the full utility service when the grid is up, while on generator power it can only pass what the generator produces. What the 200-amp panel does mean is that whole-home transfer is physically on the table. The question is how much of the house the generator carries, and what manages the rest.
How whole-home coverage works without a 48 kW generator
Two approaches cover a 200-amp panel with a residential-size generator. The first is brute capacity: a 24–26 kW unit simply carries a large home's realistic simultaneous load. The second, and the one most installers actually sell, is load management, modules that watch the generator and pause or stagger the big discretionary loads (second AC, dryer, range, water heater) for the seconds they'd overload it. Our cost guide puts load-management hardware at $300–$800 installed and notes it can let a 14 kW unit serve a house that would otherwise need 22 kW, several thousand dollars of generator traded for a few hundred of electronics.
Size bands by home profile
These starting bands come from the size classes in our cost guide; treat them as where to begin the conversation, then verify with your actual load list in the sizing calculator.
| Home profile | Starting size band | Why |
|---|---|---|
| Essential circuits only, fridge, furnace blower, well/sump pump, lights | ~10 kW | The essentials list totals far less than intuition says; motor starts, not running watts, set the floor. |
| Most of a small home, or a mid-size home with managed loads | ~14 kW | Load management sheds the spikes that would otherwise push you up two size classes. |
| Whole home, roughly 1,500–3,000 sq ft, including central air | 18–22 kW | One AC plus the normal appliance mix, with headroom for motor starts. |
| Whole home, 3,000–5,000 sq ft, all-electric, or multiple AC units | 24–26 kW | Electric heat, ranges, and dryers plus two compressors stack real running load, not just surge. |
A worked example, because 200-amp houses still have small load lists
Take the calculator's "Outage essentials" list, refrigerator (700 W running), freezer (400), gas furnace blower (800), 1 HP well pump (2,000), sump pump (800), and a whole-home lighting-and-outlets allowance (1,500). Running total: 6,200 W. Add the largest single motor surge on top, the well pump's 2,000 W start-up increment, for a starting load of 8,200 W. With 20% headroom, that's about 9.8 kW: a 10 kW class generator, behind a 200-amp panel. Add a 3-ton central AC and the same house needs about 19.2 kW with headroom, a 22 kW class machine. The full math is on our 3-ton AC page. The panel rating didn't change between those answers; the load list did.
Three traps specific to 200-amp quotes
- The nameplate fuel trap. Standby sizes are quoted on propane. On natural gas the same unit makes less: a "22 kW" Generac in our database delivers 19.5 kW on NG. If your sizing lands near a class boundary, check the rating on your fuel in the model database before signing.
- Square footage as a sizing method. It ignores the difference between a gas-heated house and an all-electric one. A 2,000 sq ft all-electric home can out-draw a 3,500 sq ft gas home; the load list knows, the floor plan doesn't.
- All-electric stack-ups. Electric range (5,000 W in our appliance data), electric dryer (5,400), electric water heater (4,500), and auxiliary heat strips (10,000) are heavy running loads, not just surges. If several must run during an outage, expect the top bands or a managed-circuits design, an EV charger (7,200 W Level 2 in our data) is almost never worth backing up.
This page is planning guidance, not a load calculation and not electrical advice. A licensed electrician should perform the actual load calculation for your service, confirm the transfer equipment and load-management design, and pull the permits, generator sizing done wrong fails exactly once, during the outage.
Sources & notes
- Size bands and load-management costs: TallyGauge cost guide (installed ranges by size class, October 2026).
- Appliance running/starting watts and the essentials worked example: TallyGauge appliance wattage dataset, the same data behind the sizing calculator; calculator method adds the largest single surge increment to running watts, then applies ~20% headroom.
- Per-fuel model ratings: TallyGauge model database.