What size generator does my Oklahoma City house need? Sizing for essentials, AC and the whole home

Generator size is a choice about comfort and cost, not a property of the house. A small home that wants central air running needs more generator than a large home that only wants the refrigerator, furnace blower, lights and internet. So the first step is a list: what must keep running in a summer storm, and what must keep running in a winter ice storm.

For most Oklahoma City households the list includes the refrigerator and freezer, the furnace blower or a few heaters, some lights and outlets, the internet and phone chargers, and, for many, the air conditioner. Homes on wells add the pump. Medical equipment goes at the top of the list if anyone depends on it.

A typical essentials list, refrigerator, freezer, furnace blower, a few lights, the internet, a microwave used occasionally and phone chargers, often lands within the range of a large portable generator, provided the loads are not all started at once. Add a well pump and the starting surge grows quickly.

Electric ranges, dryers and electric water heaters are the loads that make small generators impractical, because each draws thousands of watts. Most essentials plans leave them off and use the gas appliances or a slow cooker instead. A transfer switch or interlock lets you choose which circuits the generator feeds.

Portable generators are limited by how much an engine on wheels can produce and how long it can run between refuelings. They suit essentials plans, connected through an interlock or transfer switch so the house circuits are fed safely.

Home standby generators sit on a pad, start automatically, and commonly run from about 10 to 26 kilowatts for air-cooled residential units. They are sized from a load calculation and paired with an automatic transfer switch. National 2026 planning figures put a whole-home standby generator at about $7,000 to $15,000 installed, which includes the unit, the transfer switch and the electrical work.

The most reliable way to size a generator is a load calculation built from your panel, your appliance nameplates and the list of loads you chose, sometimes checked against a year of utility bills. It turns guesswork into a number, and it shows whether a soft starter or load management can bring that number down.

Ask anyone quoting a generator how they sized it. If the answer is the square footage of the house, ask for the load calculation instead. The right size is the one that starts your largest motor without stalling, carries what you chose, and does it on the fuel you have.