How big a generator for a
1200 sq. ft. house?
Understanding Power Requirements for 1200 sq. ft. homes
A power outage can hit at any time — and if you own a 1,200 square foot home, you've probably wondered how much generator capacity you need to keep everything running.
The short answer: more than a small portable unit can deliver, but less than most homeowners fear. With the right standby generator, your lights, air conditioning, kitchen appliances, and comfort systems stay on seamlessly. Here's how to size it correctly.
Basic Assumptions for a 1200 Sq Ft Home:
Start With Your Biggest Power Draw:
The Air Conditioner
Your 3-ton central air conditioner dominates your electrical load. A 3-ton unit draws roughly 3,000 to 3,500 watts while running — but at startup, it can surge to 6,500 watts or more for a moment. Any generator you choose must handle that startup spike without tripping offline. Generator undersizing here is the most common mistake homeowners make.
Add Up Your Electric Kitchen Appliances
Total Load Estimate for a 1,200 Sq Ft Home
Running a conservative whole-house load calculation for your setup, here's what a typical peak demand looks like:
3-ton AC (running load): ~3,500 watts
Gas furnace blower: ~600 watts
Refrigerator: ~300 watts
Microwave + small appliances: ~1,500 watts
Lighting + electronics: ~1,000 watts
Estimated peak total: ~7,200–9,000 watts, with AC startup surge capacity needed above that
That load profile points clearly to a 13kW generator as the sweet spot for whole-house coverage in a 1,200 square foot home with your configuration.
Our Recommendation:
Cummins 13kW RS13A QuietConnect
For most 1,200 square foot homes, we recommend the Cummins RS13A QuietConnect standby generator. It delivers 13 kilowatts of clean, reliable
power — enough to run your air conditioner, kitchen, lighting, and furnace blower simultaneously without breaking a sweat. Several features make it stand out from the competition.
Cummins RS13A Features
Built to withstand anything. The RS13A features a weather-resistant design that withstands winds up to 180 mph. Hurricanes, nor'easters, and severe storms — the conditions that cause outages in the first place — won't stop this unit from doing its job.
Cold-weather reliable. The RS13A operates reliably down to 0°F. When a winter storm knocks out power and temperatures plunge, this generator starts and runs without hesitation.
Fuel flexibility. The RS13A runs on either natural gas or propane, giving you the freedom to connect to your existing gas line or use a propane tank — whichever works best for your property.
Intelligent load management. Built-in smart load management automatically controls the operation of up to four high-draw loads, such as your AC, electric range, dryer, and water heater. It staggers startup sequences and balances demand, so the generator never overloads — and you never have to flip a single switch manually.
Have a Well Pump?
Step Up to the Cummins 17kW RS17A
If your home sits in a rural setting and relies on a well pump for water, consider sizing up. A well pump draws 900-2000 watts running but can surge to 2,000 to 6,000 watts on startup. Add that to your existing AC startup load and you can easily exceed 13 kW of peak demand at the worst possible moment.
We recommend the Cummins 17kW RS17A QuietConnect for rural homeowners. It carries the same weather-resistant 180 mph wind rating, cold-weather operation to 0°F, natural gas or propane flexibility, and intelligent load management for up to four loads — but it gives you 4 additional kilowatts of headroom to absorb that well pump surge comfortably.
Running on a well means water security during extended outages, and the RS17A ensures you never have to choose between your AC and your tap.
Don't Forget Professional Installation
A properly sized generator is only half the equation. Correct installation — with a code-compliant automatic transfer switch, proper gas line sizing, and safe placement — determines whether your investment performs when you need it most.
Our licensed electricians at Benchmark Electric handle the complete installation process, from load calculations to final inspection, so you can trust your system the moment the power goes out.
Ready to stop guessing and
start protecting your home?
Contact Benchmark Electric today for a free whole-house load assessment. We'll confirm the right Cummins generator for your specific needs and get it installed by a certified pro. Call us or request a quote online — your next outage doesn't have to be a disaster.
Learn more about standby power: