Generac Home Standby Generators: Sizing Guide

An independent guide

Many homeowners start their search with a brand name, and Generac comes up often. This site is not a dealer, so we have no product to push. The contractor we pass your request to may install Generac or other brands. Ask them which brands they are trained and authorized to install and service, since that can affect warranty coverage.

Lightning strikes from dark storm clouds above a brick suburban house

How Generac home units are grouped

Generac's air-cooled Guardian series is the line most people mean when they say a Generac home generator. It comes in a range of kilowatt sizes, from smaller units suited to essential circuits up to larger ones in the mid 20 kW range that can run many whole homes. Generac also makes liquid-cooled units for larger homes and heavier loads. Model names, sizes and features change over time, so check the current lineup on Generac's own site or with your installer.

Sizing a Generac (or any brand)

The right size comes from a load calculation, not the house's square footage alone. The installer lists what must run during an outage, such as the furnace or boiler, well pump, sump pump, fridge, central air and cooking, and adds up running and starting loads. Generac and other brands offer load management modules that let a smaller generator cover more of the house by holding back big loads until there is spare capacity. Ask to see the calculation.

What size do you recommend, and what will and will not run?
Is my gas meter big enough, or will the utility need to upgrade it?
Which transfer switch and load management parts are included?
Are you authorized to handle warranty work for this brand?
Who registers the warranty, and how long is it?
What does yearly maintenance cost, and do you offer it?

Fuel and placement

Most Generac home units run on natural gas or propane. Output is usually a bit lower on natural gas than on propane, and the spec sheet lists both. Placement must follow the manufacturer's clearances from windows, doors and vents plus local setback and noise rules. See our fuel options guide for more.

Smart features and monitoring

Many newer Generac home units can connect to Wi-Fi so you can check status and alerts from a phone app. That is useful if you travel or have a second home, since you can see whether the unit ran its self-test or has a fault. Ask your installer how monitoring is set up and whether there is any subscription cost.

Getting a quote

If you have a Generac model in mind, mention it on the estimate form. We pass your request to an independent local contractor, who can tell you whether that model fits your house or suggest an alternative. You decide what to buy.

Questions homeowners ask

Is Briarcliff Generators a Generac dealer?

No. This is an independent website and is not affiliated with Generac. The contractor you are connected with can tell you which brands they are authorized to install.

What size Generac do I need for my house?

It depends on what you want to run, not just the size of the house. A load calculation from an installer is the reliable way to pick a size. Ask for it in writing.

Does a Generac run on natural gas or propane?

Generac home standby units are generally built to run on either natural gas or propane, set up at installation. The output rating is usually a little different for each fuel, and the spec sheet lists both.

Who handles warranty repairs on a Generac?

Warranty work is generally done through the manufacturer's authorized service network. Ask your installer whether they are authorized for warranty service on the model you are buying.