How to Choose the Right Size Generator
CR's experts help you select the right type and size of generator to keep the electricity flowing during an outage
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When the power goes off, whether it’s because of a hurricane or heat stress on the power grid or just one downed tree, a generator can be a lifesaver.
If your TV won’t turn on when "The Bachelorette" is airing, it’s annoying but not much more than that. If your sump pump stops and your basement floods, you’re looking at a costly repair. And if you have an oxygen machine or other critical medical device, having a backup source of power can be important.
Using a Generator Safely
Before we get to the specifics, here are a couple of notes on safety. Consumer Reports tests only portable generators with carbon monoxide (CO) safety technology—that is, a built-in sensor that triggers an automatic shutoff if carbon monoxide builds up to dangerous levels in an enclosed space. We recommend that you only use a generator with this feature.
With any generator, it’s extremely important to follow safe practices, as described in detail by the Consumer Product Safety Commission. Never operate a generator indoors, including in a garage or carport. Operate your generator a minimum of 20 feet from your home with the exhaust directed away from it as well as from any windows, doors, and AC units.
Add Up Your Wattage Needs
To determine the size generator you need, make a list of the appliances you want to power and add up their wattages. And here’s a tip: If you’re considering a portable generator, don’t spring for one that produces a lot more power than you’ll be using.
“There’s no need to go larger unless you want to be able to power more in a pinch and are comfortable with needing to keep more gas on hand,” says Misha Kollontai, a Consumer Reports engineer with long experience in generator testing. Some of the larger portable generators in our ratings can burn through about 20 gallons of gasoline per day.
Depending on the size generator you need, you may have a choice between a traditional portable generator and an inverter generator, which electronically throttles the engine up and down to supply power more efficiently. “If you’re willing to pay more up front for a quieter and more fuel-efficient unit, potentially saving down the road if you use it often, then look at inverters,” Kollontai says.
The interactive tool below will help you estimate how powerful a generator you need. Just click on a type of generator to get a sense of what appliances 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. Also keep in mind that some appliances—air conditioners, refrigerators, and sump pumps, for instance—draw a lot more power at the moment they’re cycling on. These surge watts can throw off your calculations if you don’t account for them.
What a Generator Can Power
Click on any type of generator below to see what it will run in your home.
Recreational
Inverter
Inverter
or Portable
Standby
Another way to think about your generator choices is to consider how often you’re likely to need one, and for how long. That’s unpredictable to an extent, of course, but think about the outages you experienced in the past and what devices you needed to power. Then see which of the three power-outage scenarios below match your situation.
You can click on any generator type to jump down to a list of its pros and cons, as well as a specific product recommendations.
1. You Experience Frequent Power Outages
And when the power goes off, the outages are sometimes prolonged. This probably applies if you live in an area prone to severe weather events, such as blizzards, ice storms, tornadoes, and hurricanes, where a large number of homes may be affected at the same time.
Generator Types to Consider
• Home standby
• Large inverter
• Large portable
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 you need them to work in a power outage, you’ll need a transfer switch installed at your breaker box to hook up a large portable or inverter generator.
A licensed electrician should be able to handle the job, but be sure to budget for that installation cost when considering the cost of the generator. A home standby generator also needs costly professional installation, with the transfer switch generally included in the price.
2. You Have Occasional Outages
Sometimes they’re sustained, but not typically, and you don’t want to spend many thousands on a home standby generator.
Generator Types to Consider
• Large inverter
• Large portable
Unless you experience numerous power outages a year, you might not be willing to spring for the $10,000 or more it can cost to buy a home standby generator and have it installed. You can save thousands of dollars if you’re willing 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 and budget for that expense.
3. You Rarely Lose Power
Even so, you want a generator for some peace of mind, and to power a few important items.
Generator Types to Consider
• Midsized inverter
• Small 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 above. Small recreational models are compact enough to toss into the back of a pickup to power a TV and cooktop or a small fridge at a tailgate, and can be used to charge phones and laptops, as well as lamps and small kitchen appliances.
More Generator Details
Here’s what you need to know about each type of generator, along with info on specific products that do well in Consumer Reports’ testing.
Midsized Inverter
2,000 to around 3,500 watts
$500 to $2,400
Pros: Midsized inverter generators are quiet and lightweight. (Most models weigh less than 150 pounds.) They’re also efficient, capable of keeping the fridge running and the lights on for 8 to 25 hours using only 2 to 3 gallons of gas.
Cons: These inverter generators 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 of money.
Small Inverter Generator
Up to around 2,000 watts
$450 to $1,600
Pros: Small inverter generators are lightweight, typically coming in around 60 pounds. They are extremely quiet, have no installation costs, and are 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. And you can use them while camping or tailgating to run anything from a TV to a fridge.
Cons: These generators have enough capacity to power a fridge, some lights, and a phone charger but not much else. They 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 with more capacity.
Large Portable
Up to 8,500 watts
$950 to $2,000
Pros: Portable generators can provide great value—you get a lot of power for the money. Some large models produce enough energy to meet all the power demands in a home. They 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 can cost several hundred dollars. Large portables are also noisier than large inverter generators and home standby generators. They usually run only on gasoline and use a lot of it compared with inverters. And they’re bulky; many weigh around 250 pounds. They shouldn’t be used in rain or snow without protection, such as an open-sided tent.
Large Inverter
5,000 watts to around 7,500 watts
$1,300 to $7,000
Pros: Large inverter generators produce enough energy to run a refrigerator, lights, and other essentials, such as a furnace or small central air-conditioning unit. They can be connected to your breaker panel to run hardwired equipment, such as a well pump. They’re quiet and produce steady power, which is ideal for sensitive electronics, such as stereo equipment. And they’re fuel-efficient.
Cons: They’re expensive. Only models costing $2,400 or more perform well enough in our tests to warrant serious consideration. And that connection to your home’s electrical panel will add significantly to the cost. And you’ll need to keep plenty of stabilized gasoline on hand.
Home Standby
Up to 20,000 watts
$2,000 to $6,000
Pros: Home standby generators are permanently installed (usually next to the house) and kick on automatically during an outage to provide uninterrupted current. They can power everything in a typical home simultaneously, up to their maximum output. Standby generators 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, standby generators are more expensive than other types of generators. Installation can be complex, including building a stable concrete footing and running both gas and electrical connections. Installation costs run into the thousands—and those costs are not included in the prices we list here. They can’t be installed in low-lying areas prone to flooding—and can’t be moved if they do flood.
