How to Choose the Right Size Generator

CR's experts help you find the best model for backup power when the lights go out

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illustration of lit up house plugged into a generator Illustration: Consumer Reports

The typical American endures an average of 8 hours without power each year because of unplanned outages. That may not sound like much, but it’s more than double what that number was in 2013 according to the U.S. Energy Information Administration, suggesting the problem of outages is getting worse, not better. And some power outages, such as those caused by extreme weather, can last for days or even weeks.

When they do, homeowners can face a long list of inconveniences and expenses, including spoiled food, frozen pipes, flooded basements, and moldy walls.

More on Generators

A generator is a first line of defense against these problems. But with models ranging from small recreational units that start at about $450 and can power a single appliance to standby models—also sometimes called a whole-house or home standby generator—that can cost $5,000 or more and power an entire house, choosing a generator can be daunting.

“Buy the smallest generator that will meet your power needs,” advises Dave Trezza, a Consumer Reports test engineer. “That will minimize the amount of fuel you need to keep on hand to run it.” For reference, some of the larger portable generators in our ratings can burn through about 20 gallons of gasoline per day.

But how do you figure out which generator is right for your needs? Keep reading.

Here, we offer guidance on how to choose the generator that’s right for your situation, details on each category of generator we test, and a CR recommendation and product review in each category.

A Word on Wattage

One way to answer the question of which size generator you need is to add up the wattages of everything you want to power during an outage. That will give you a rough approximation. But before you bust out the calculator, keep in mind that some appliances—air conditioners, refrigerators, and sump pumps, for instance—draw a lot more wattage in the moment when they're cycling on. These surge watts can throw off your calculations if you don't account for them.

We've done that for you in the interactive tool below. Just click on a type of generator to get a sense of what you can run with it. The wattages for each type of appliance are general guidelines and may vary from what you have in your home.

What a Generator Can Power

Click on any type of generator below to see what it will run in your home.

Large Inverter
or Portable

Another way to think about choosing the right size generator for your home is to consider how often you're likely to need one—and for how long. That's unpredictable to an extent, of course, but see whether any of the three power-outage scenarios below match your situation.

You can click on any type to jump down to a list of its pros and cons, as well as a specific product recommendation and review for each.

1. You Experience Frequent Power Outages

Even worse, the outages are sometimes prolonged. This also applies if you live in an area prone to severe weather events, such as blizzards, ice storms, tornadoes, and hurricanes.

Generator Types to Consider
Home standby
Large inverter

These three types have enough juice to power your entire household, and they can connect directly to your home’s circuit breaker panel, allowing you to control and run appliances that are hardwired, such as central heat and air conditioning, well pumps, sump pumps, electric ranges, and water heaters. If you have any of these and it’s essential for them to work in a power outage, be sure to have a transfer switch installed at your breaker box. A licensed electrician should be able to handle the job.

2. You Have Occasional Outages

Sometimes they're sustained, but not typically, and you don’t want to spend thousands on a home standby generator.

Generator Types to Consider
Large inverter

Unless you experience numerous power outages a year, you may not be willing to spring for the $10,000 or more it can cost to buy a stationary unit and have it installed. You can save thousands of dollars if you don’t mind having to pull your large inverter or portable generator out of a garage or shed and hook it up during the outage. You'll still want to have a transfer switch installed.

3. You Rarely Lose Power

Even so, you want a generator for some peace of mind.

Generator Types to Consider
Midsized inverter
Recreational inverter

Midsized inverter generators have ample power to run a fridge and a window AC or space heater, as you can see in our interactive tool. Recreational models are compact enough to toss into the back of a pickup to power a TV and cooktop at a tailgate. Go Wildcats!

Safety First

Consumer Reports recommends only portable generators with a built-in sensor that triggers an automatic shutoff if CO builds up to dangerous levels in an enclosed space.

With any generator, it’s extremely important to follow our long-standing advice of always operating a generator a minimum of 20 feet from your home with the exhaust directed away from it as well as from any windows, doors, AC units, or other structures.

Recreational Inverter
Up to 2,000 watts
This is the lightest type of generator. (Most models weigh around 60 pounds.) It’s extremely quiet, has no installation costs, and is easy to store and transport. You can pair most units to increase output. Many come with user-friendly features such as fuel-level indicators and smartphone apps.

Cons: It’s enough to power a fridge, some lights, and a phone charger, but not much else. It can’t be connected to a circuit breaker panel or used to power any device that doesn’t have a standard plug. The most expensive models cost as much as a portable generator, which can do far more.

Midsized Inverter
Up to 3,500 watts
It’s lightweight (most models weigh less than 150 pounds) and quiet. It’s also efficient, capable of keeping the fridge running and the lights on for 8 to 18 hours using only 2 to 3 gallons of gas.

Cons: It can generally power only 110-volt items with a standard two- or three-prong plug, ruling out well pumps, and heating and cooling equipment. You can now find special 110-volt transfer-switch kits, but the installation cost makes them an impractical choice because you could opt for a portable generator with a 220-volt transfer switch for the same amount.

Up to 7,500 watts
It’s the best value in terms of cost vs. capacity. Certain models produce enough energy to meet all the power demands in a home. It can be connected to a breaker panel with a transfer switch to run hardwired equipment, such as a well pump.

Cons: Making the connection to your home’s circuit breaker panel costs as much as the generator itself. It’s noisier than large inverter and home standby generators. It usually runs only on gasoline and uses a lot of it compared with inverters. And it’s bulky; most weigh close to 300 pounds. It shouldn’t be used in rain or snow without protection, such as an open-sided tent.

Large Inverter
Up to 7,500 watts
It produces enough energy to run a refrigerator, lights, and other essentials, such as a furnace or small central air-conditioning unit. It can be connected to your breaker panel to run hardwired equipment, such as a well pump. It’s quiet and produces steady power, which is ideal for sensitive electronics, such as stereo equipment. And it’s fuel-efficient.

Cons: It’s expensive. Only models costing $3,000 to $4,000 perform well enough in our tests to warrant serious consideration. And they can’t run on natural gas or propane, so you still need to keep stabilized gasoline on hand.

Home Standby
Up to 20,000 watts
It’s permanently installed (usually next to the house) and kicks on automatically during an outage to provide uninterrupted current. It can power everything in a typical home simultaneously, up to its maximum output. It can be set up to run indefinitely on natural gas or can be fueled by propane. There’s no need to connect cables, flip a switch, or start the engine.

Cons: With few exceptions, it’s more expensive than other types of generators. Installation costs can run into the thousands—and they’re not included in the price range we list above. It can’t be installed in low-lying areas prone to flooding and can’t be moved in the event of a flood.

Editor's Note: A version of this article also appeared in the September 2018 issue of Consumer Reports magazine. It has been updated to reflect new safety advice and newly tested models.

Generator Tips

Damaging storms can happen anytime. On the "Consumer 101" TV show, host Jack Rico learns from Consumer Reports’ expert Paul Hope how to avoid being left in the dark during a power outage.

Paul Hope

As a classically trained chef and an enthusiastic DIYer, I've always valued having the best tool for a job—whether the task at hand is dicing onions for mirepoix or hanging drywall. When I'm not writing about home products, I can be found putting them to the test, often with help from my two young children, in the 1860s townhouse I'm restoring in my free time.