What size generator do I need for my house?
It depends on what you want running during an outage, not on the square footage of your home. Most homeowners choose between two directions: a whole-home system that powers everything, including central air conditioning, or a smaller system that covers essential circuits like the refrigerator, sump pump, and heat. Generators are rated in kilowatts, and the right rating comes from what your home actually runs.
The most reliable way to get the size right is a site evaluation. At Corrigan Generators, a project manager looks at your panel, gas service, and equipment, then recommends only what your home truly needs.
Why can't I size a generator by square footage?
Because two houses of the same size can have very different power demands. What your home runs matters far more than how big it is. The biggest factors include:
Central air conditioning, which draws more than almost anything else in a house
Electric water heating
Electric ranges and ovens
Well pumps and sump pumps
The age and capacity of your furnace, water heater, and air conditioning
Any medical equipment in the home
Many homeowners call with a size in mind, usually one they saw at a neighbor's house. That is a fine starting point, but your neighbor's home may run very different equipment than yours.
What does a whole home generator power?
A whole home generator keeps your entire house running, including central air conditioning, electric water heating, ranges and ovens, and everything else, so an outage barely registers.
If keeping your family cool is a priority, whole home is almost always the right choice. Air conditioning is what moves a home into whole-home capacity, which is why it is the deciding factor for most homeowners.
What does an essential circuits generator power?
An essential circuits generator powers the things that keep your home livable and protected, not the entire house. That usually means:
Refrigerators and freezers
Sump pumps
Heat
Well pumps
Garage doors
Lighting and outlets in the rooms you actually live in
It is a smaller system and a smaller investment, with enough power to stay comfortably in your home through an outage.
How do I choose between whole home and essential circuits?
Start with air conditioning, then work through the rest of your priorities. A few questions help most homeowners narrow it down:
Is staying cool during a summer outage important to your household?
Does anyone in your home depend on powered medical equipment?
Do you rely on a sump pump or a well pump?
Which rooms does your family actually use during an outage?
What fits your budget?
Sometimes the difference between the two directions is smaller than homeowners expect. If whole home coverage is within reach of what you were already prepared to spend, we will tell you before you decide.
What happens if a generator is the wrong size?
A system that is too small may not keep up with everything you expected it to run, and a system that is too large adds cost without adding protection. Both lead to the same place: a homeowner who is not satisfied years later.
In more than twenty years of installing and servicing standby generators, we have found that sizing is the part of the decision that determines whether a customer is happy with their system long after the install. That is why it leads every recommendation we make.
Why isn't an online size calculator enough?
A calculator only knows what you type into it. It cannot see your electrical panel, check your gas service, or tell you where a generator can legally sit on your property.
Real sizing also has to account for:
The age and capacity of the equipment you already have
Whether your gas service can support the unit, or needs a meter upgrade
Clearance from windows and doors, and proper ventilation
The route between your gas and electric meters
A pad location that keeps the system accessible and your landscaping intact
How does Corrigan Generators size a home generator?
A Corrigan project manager walks your home with you, inside and out. Inside, we review your electrical panel, your gas service, and the equipment you already have. Outside, we identify where the generator can be placed safely and legally.
Then we give you a detailed recommendation of the system that will work for your home and explain clearly why we selected it. In many cases, that is a smaller system than the homeowner expected. Nobody here is paid on commission, and we do not use incentive pricing.
Once the size is set, the brand conversation follows. We are a certified dealer and service provider for Briggs & Stratton, Generac, and Kohler, and we compare the details that matter to you, including warranty terms, sound levels, footprint, and lead times.
Does generator size affect the cost?
Yes. Size is one of the biggest factors in what a generator project costs. The total also depends on where the unit can be placed, whether you need a gas meter upgrade, and how far the gas and electric have to run.
That is why we do not publish pricing. You receive the full number in writing after your site evaluation, and nothing is committed until you approve it.
How do businesses size a standby generator?
The same way: by what has to keep running. Refrigeration, point-of-sale systems, medical equipment, lighting, heating and cooling, and security systems all carry different demands. We evaluate the building and its equipment, then size an air-cooled or liquid-cooled system to what the operation requires.
Home Standby Generators in Louisville and Southern Indiana
Corrigan Generators sizes, installs, and services home standby generators across Kentucky and Southern Indiana, including Louisville, Jeffersontown, Prospect, Shelbyville, La Grange, Elizabethtown, New Albany, and Jeffersonville. Every system we install includes remote monitoring, the first year of service and monitoring, a cold weather kit, and a solid pre-formed concrete pad.
We are the generator division of Corrigan Electric, family-owned since 1995, and we have worked on generators since 2004. Request an appointment online or call 502-267-4600, Monday through Friday, 7:30 AM to 5:00 PM. A member of our team follows up within 24 hours, Monday through Friday, excluding holidays.
Is there a special on Briggs & Stratton generators right now?
Yes. To celebrate the launch of Corrigan Generators, we are offering $1,500 to $2,200 off the normal proposal price of a Briggs & Stratton standby generator, based on the size of the unit selected. Your deposit must be received by the end of the day on November 30, 2026, to qualify.
Because the site evaluation, recommendation, and written proposal come before the deposit, now is a good time to request your appointment.
Savings based on unit size. Off normal proposal price. Deposit must be received by end of day 11/30/26.
Frequently Asked Questions
Will a generator power my entire home?
It can. Whether it should depends on what you want running and what fits your budget. If central air conditioning is a priority, you are generally looking at a whole home system. If your focus is refrigerators, sump pumps, and heat, a smaller essential circuits system may be the better use of your investment.
What size generator do I need to run central air?
Central air conditioning usually points to whole-home capacity, because cooling draws more power than almost anything else in a house. The exact kilowatt rating depends on your air conditioning and the rest of your equipment, which we confirm during the site evaluation.
Can a generator be too big for my house?
Yes. A larger system than your home needs adds cost without adding protection. We recommend only what your home truly needs, and in many cases that is a smaller system than the homeowner expected.
What if someone in my home uses medical equipment?
Tell us at the site evaluation. Circuits for oxygen, ventilators, powered beds, mobility equipment, and refrigerated medication come first in the sizing conversation, and we build the recommendation around them.
Get the Size Right the First Time
The right generator is the one sized to your home, your priorities, and your budget, not the one at the house down the street. A site evaluation takes the guesswork out, and you get the full recommendation and price in writing before you decide anything.
👉 Request an appointment with Corrigan Generators today, or call 502-267-4600.
You know us at Corrigan, Give us a call. Your Generator Dealer & Service Provider!