Generator sizing Last reviewed June 2026

What Size Generator for a 200 Amp Service?

By the WhatSize editorial team 5 min read Standards-reviewed

TL;DR

A 200 amp electrical service can deliver up to 48,000 watts, but you should never size a backup generator to the full panel rating. For essential loads only (fridge, freezer, sump pump, furnace blower, lights, internet), a 15-25 kW standby generator is typical. For whole-house coverage, 25-50 kW.

Looking for a different size? See What Size Generator for a 2,000 Sq Ft House? or browse all generator sizing guides.

Why 200 amp service matters for generator sizing

Your home's amperage service (100A, 150A, 200A, 400A) is the maximum total current the utility can deliver. Most US homes built after 1990 have 200A service. The service rating doesn't tell you what your typical load is — it tells you the ceiling. A 200A home might normally draw 30-50A, with peaks of 100-150A when the AC and dryer run together.

For backup generator sizing, you have two strategies:

Whole-house coverage: generator handles every circuit. Requires a transfer switch + a generator sized to your peak load. For a 200A service, that's typically 25-50 kW.
Essential-circuits only: generator handles a sub-panel of 8-16 critical circuits (fridge, freezer, sump pump, furnace blower, well pump, internet, lights). For most 200A homes, this is 15-25 kW.

Whole-house is more convenient but 2-3× the cost. Essential-circuits is the most common residential choice.

Top picks for this size

BEST OVERALL

DuroStar DS13000MX 13,000W Dual Fuel #ad

13,000W, Dual Fuel, Electric Start, Whole Home Backup

★★★★☆ 4.6 · 177+ ratings

Dual Fuel (Gas/Propane)13,000W PeakElectric Start

$899 approx

Check price

MID-RANGE

Westinghouse 5000W Dual Fuel Inverter #ad

★★★★☆ 4.7 · 19.3K+ · $949

Amazon

These Amazon-available picks meet the calculated spec. For region-specific or licensed contractor-installed options, consult a local professional. See our Disclaimers.

Sizing chart by strategy

200 amp service — generator sizing by strategy

Strategy	Generator size	Typical cost (installed)
Essential circuits (8-16)	15-25 kW standby, 10-15 kW portable	$2,000-5,000 portable, $5,000-12,000 standby installed
Whole house (managed load)	25-40 kW standby	$10,000-20,000 installed
Whole house (full coverage)	40-50 kW standby	$15,000-30,000 installed

Quick load math for essentials

Add up the running watts of the appliances you want to back up:

Refrigerator: 150-400W (1,200W starting surge)
Freezer: 100-300W (1,000W starting surge)
Sump pump (1/2 HP): 600-900W (2,000W starting surge)
Furnace blower (1/2 HP): 600W (1,500W starting surge)
Well pump (1 HP): 1,000W (3,000W starting surge)
Lights (10 LEDs): 100W
WiFi router + internet: 30W

Typical essential load: 2,500-3,500W running, 6,000-8,000W starting. A 10-15 kW portable generator handles this with margin. A 15-25 kW standby handles it with comfortable margin and the ability to add a window AC or extra circuits.

Use our free generator calculator for your exact appliance list.

Frequently asked questions

Will a 200 amp service run on a 15 kW generator?

A 200A electrical service delivers up to 48,000W, but no generator in the 15 kW range can run every circuit at once. A 15 kW generator is correctly used with a transfer switch to power only a sub-panel of essential circuits (typically 8-16 circuits). The full 200A panel is not energized.

What size generator for a 200 amp house?

For essential circuits only: 15-25 kW. For whole-house managed load: 25-40 kW. For full-coverage whole-house: 40-50 kW. Most homeowners choose essential-circuits because the cost difference is 2-3×.

Is 200 amp service standard for new homes?

Yes — 200A has been the standard residential service in the US since the 1990s. Older homes may have 100A or 150A service, and some luxury homes have 300-400A. The generator sizing math scales with the service rating, but most homes peak well below their service rating.