Generac Standby Generators: Sizes, Features & How to Choose (2026)

A Generac standby generator is a permanent backup power system that starts by itself when the grid goes down. You do not wheel it out, pull a cord or pour gasoline. It sits beside your house, watches the utility power, and takes over within seconds. For many families that is the whole point.

Here is the short version. Generac’s current air-cooled home standby line runs from 10 kW to 28 kW. The units run on natural gas or propane, carry a 5-year limited warranty on their listings, and the newest generation adds built-in cellular monitoring and longer service intervals. Most homes land on 18 to 24 kW. Smaller homes can use 10 to 14 kW, and large homes with several air conditioners need 26 or 28 kW.

This guide explains how standby power works, what changed when Generac replaced its Guardian series, how to pick a size, what the transfer switch does, and what to plan for before installation. You will also find three current models with direct links, so you can see real listings instead of brochure talk.

What Is a Generac Standby Generator?

A standby generator is a small power plant that lives outside your home, on a pad, connected to your electrical panel and your gas supply. It has three main parts:

• The generator. An engine and alternator inside a weatherproof enclosure.
• The automatic transfer switch. A box near your electrical panel that senses when utility power fails and switches your home over to generator power.
• The fuel supply. Your home’s natural gas line or a propane tank. There is nothing to refill by hand.

When the power goes out, the transfer switch notices, the generator starts, and your home runs on generator power. When the grid comes back, the system switches over again and the generator shuts down. You may be asleep or a thousand miles away, and it still works.

That is the big difference from a portable generator, which someone must roll outside, fuel and start. Our guide to portable vs standby generators compares the two in detail.

Generac describes itself as the number one selling brand of home standby generators and has been in the power business since 1959. That size matters in one practical way: dealers and service technicians are easy to find in most areas.

Guardian vs Next Gen: What Changed in 2025

If you have shopped for a Generac before, you know the Guardian name. In 2025 Generac introduced its Next Gen home standby line as the successor to the Guardian series. You will still see Guardian models for sale while stock lasts, so it helps to know what is new.

One detail to check before you buy: the Amazon listings say remote monitoring and control through the Mobile Link app requires a Mobile Link premium subscription. Ask your dealer exactly what is included.

Key insight: the generator is only half the system. The transfer switch, the gas supply and the installation decide whether it works on the day you need it.

Generac Standby Sizes: 10 kW to 28 kW

Standby generators are rated in kilowatts. One kilowatt is 1,000 watts. Each size has two ratings, because the same engine makes a little more power on propane than on natural gas.

There is also a 20 kW three-phase version for homes and small businesses with three-phase service. Above 28 kW, Generac moves to liquid-cooled models, which are a different class of machine.

What Size Generac Standby Generator Do You Need?

Sizing a standby generator is a job for your installer, who will do a proper load calculation. You can still walk in knowing roughly where you will land.

1. Decide what “backed up” means to you. Essentials only, most of the house, or everything exactly as normal?
2. List your big loads. Central air conditioners, electric water heaters, electric ranges, dryers, well pumps and EV chargers decide the size.
3. Count your air conditioners. Each central unit needs a large burst of power to start. This is usually the deciding factor.
4. Check your electrical service. Many homes have 200-amp service, which pairs with a 200-amp transfer switch.
5. Ask about load management. A smart transfer switch can hold back big loads so a smaller generator can cover the whole house.

As rough guidance only: 10 to 14 kW suits smaller homes and essential circuits, 18 to 24 kW covers most family homes with one central air conditioner, and 26 to 28 kW suits large homes with two or more air conditioners or many electric appliances. Your installer’s calculation always wins over a rule of thumb.

Want a head start before the site visit? Our Generator Size Calculator adds up your appliances, and our guide to whole-house generators explains sizing, fuel and installation step by step.

Natural Gas or Propane?

Every model in the table runs on either fuel. The right one is usually decided by what your home already has.

Natural gas

If you have natural gas service, use it. The supply is continuous, so the generator can run for days without anyone hauling fuel. Output is slightly lower than on propane, as the table shows. Your installer must confirm that your gas meter and piping can feed the generator along with your furnace and other appliances.

Propane

If you are not on a gas main, propane is the answer. It stores for years without going bad and gives the generator its full rating. The limit is the tank. A standby generator under load drinks propane quickly, so the tank must be sized for the number of days you want to ride out. Your propane supplier and installer should work that out together.

Either way, there is no gasoline to store, rotate or spill. That is one of the quiet advantages of standby power.

Transfer Switches Explained

The automatic transfer switch is the brain of the system. It is also what makes standby power safe, because it disconnects your home from the utility lines before the generator feeds your panel.

• 200-amp whole-house switch. Backs up your entire panel. This is what the bundled Amazon listings include.
• 100-amp, 16-circuit switch. Backs up only the circuits you choose. Dealer documentation lists it for the 14 kW size.
• Generator without a switch. For homes that need a different switch, such as one for 400-amp service. Your installer supplies the right one.

Buying the generator and switch as a bundle is usually simplest. Just make sure the switch matches your electrical service before you order. Your electrician can tell you in one phone call.

The Best Generac Standby Generators for Most Homes

Here are three current models that cover small, typical and large homes. All three listings include a 200-amp automatic transfer switch.

Need a generator without a switch, for example to pair with a 400-amp service? The same family is listed without a transfer switch too, such as the Generac 28kW model 7282.

What It Really Costs to Own One

We do not quote prices here, because the generator is only part of the bill. What you actually pay depends on these pieces:

• The generator and transfer switch. The part you see on a listing.
• Site work. A level pad or base where the unit will sit.
• Electrical work. Wiring the transfer switch into your service, which is harder if the panel is far from the generator.
• Gas plumbing. A new gas line, and sometimes a meter or regulator upgrade, or a propane tank.
• Permits and inspections. Required in most places.
• A battery. The starting battery is often bought separately.
• Ongoing service. Oil and filter changes and an annual check.

Get at least two written quotes that list every item. If one quote is far lower than the others, find out which line it left out.

Installation: What to Expect

A standby generator is not a weekend project. It ties into your electrical service and your gas supply, and both are regulated for good reasons. A typical installation goes like this:

1. Site visit. The installer checks your panel, gas supply and yard, and does the load calculation.
2. Permits. The installer pulls electrical and gas permits, and checks any homeowner association rules.
3. Placement. The unit goes on its pad, outdoors, at the clearances required by the installation manual and local code.
4. Electrical and gas hookup. The transfer switch is wired in and the fuel line is connected and pressure tested.
5. Startup and activation. The system is tested with a simulated outage, and you are shown how it works.
6. Inspection. The local inspector signs off.

Monitoring and Maintenance

A standby generator spends almost all of its life waiting. Maintenance is what makes sure the waiting pays off.

• Let it exercise. Standby generators run themselves briefly on a schedule to stay ready. Do not switch that off.
• Watch the app. The Next Gen line has cellular, Wi-Fi and Bluetooth built in and reports through Mobile Link, so you can see problems before the storm arrives.
• Change the oil on time. Generac dealer documentation gives the Next Gen line a 200-hour oil change interval. In a long outage that is about eight days of nonstop running.
• Keep it clear. Remove snow, leaves and weeds from around the enclosure so it can breathe.
• Check the battery. A weak battery is one of the most common reasons a standby generator fails to start.
• Book an annual service. A dealer check once a year catches small issues early.

Our generator maintenance checklist covers the routine jobs for any generator.

Common Mistakes When Buying a Standby Generator (and the Fix)

Pro Tips From the Paperwork

These tips come from manufacturer documentation and standard installer practice.

• Ask about load management first. It can move you down a size, which saves money on the unit and on fuel.
• Think about where the noise goes. Place the unit away from bedrooms and from your neighbors’ windows, within the rules.
• Check your HOA rules early. Some associations have rules on placement and screening.
• Register the warranty as soon as the system is activated.
• Keep a spare oil and filter kit on the shelf. During a week-long regional outage, parts sell out fast.
• Know your manual shutdown. Have the installer show you how to switch the system off safely for service or in an emergency.
• Protect it in winter. Ask the dealer whether a cold-weather kit makes sense for your climate.

Real-Life Scenarios: Which Size Fits?

These are typical situations that homeowners describe when they shop for standby power. They are examples to help you choose, not quotes from real people.

Generac Standby Generators: FAQ

Your Standby Generator Checklist

• Decide whether you want essentials, most of the house or everything backed up.
• List your big loads and count your central air conditioners.
• Find out whether your service is 100, 200 or 400 amps.
• Choose your fuel: natural gas if you have it, propane if you do not.
• Get at least two written quotes with a load calculation.
• Ask each installer about load management and a smaller unit.
• Confirm what the monitoring app includes and what it costs.
• Use licensed professionals, with permits and an inspection.
• Register the warranty and book the first annual service.

Sources: Generac dealer documentation for the Next Gen home standby line (Norwall PowerSystems); Amazon product listings for Generac models 7323, 7325, 7329 and 7282, all checked October 2026.