Generator Buying Guide

When the power goes out, a generator can keep your house warm in winter or cool in summer; it can keep your food cold, your kitchen cooking, and your computers and phones charging. Assuming you have one.

People tend to buy generators around major storms, when they’re prone to making a desperate decision—without a plan for what to do when they get it home. Working by flashlight, in a rush to get the power up and running, they might skip over critical safety steps during setup. And people die every year from carbon monoxide poisoning related to generators.

We don’t want you—or anyone relying on a generator—to be one of those people.

Know Your Power Priorities

Generators are sold by power output, as measured in watts. The amount of power they deliver determines how many lights and appliances you can run at once; the quality and consistency of that power determines how well they'll run. Figure on about 5,000 watts to cover the basics in a typical home.

Start by making a list of what you don't want to go without while the power's down, then add up their watts to get you in the right ballpark. Here are some rough numbers for common essentials:

Refrigerator: 600 watts
Sump pump: 750 to 1,500 watts
Portable heater: 1,500 watts
Window air conditioner: 1,000 watts
Lights: 60 to 600 watts
Computers: 60 to 300 watts

For a more complete list, check out our report on how to pick the right size generator for your house.

One tip that will make prioritizing easier is to determine which outlets and appliances are controlled by each circuit breaker in your panel, and label them accordingly. The easiest way: a small electric device called a digital circuit breaker finder, which you can buy for less than $50. 

Pick a Type

You can go one of four ways. Home standby generators are installed permanently, can run on natural gas or propane, and kick on automatically during an outage. Portable and inverter generators can both be moved around, and they come in different sizes. Some are better for transporting to a tailgate, while others are better kept on your property as a backup power source. And portable power stations are large batteries that store electricity for when you need it, the only option for someone who lives in an apartment, say, and has no way to safely run a generator outdoors.

A standby generator.

Home Standby Generators

• These units cost the most money and should be installed by a pro (so factor in labor costs). An experienced electrician can help with town or municipal permits, noise restrictions, and proper location.

• These start automatically when the power goes out, and typically supply more power than the other four options.

• They run a self-diagnosis and let you know when maintenance is needed. Some even do this via email or text, to you or your dealer.

• You have your choice of fuel— propane, which is less risky to store than the gasoline required for the other models here, or natural gas, which provides an unlimited supply of power. 

• They range from roughly 5,000 to 20,000 watts. 

Typical cost:
$2,000 to $6,000 without installation, which can double these prices

Home Standby Generators Ratings
A portable generator.

Portable Generators

• These units tend to cost less than home standby generators.

• They typically run on gasoline that you may need to store in large quantities. Stabilizer must be added to your fuel for prolonged storage. 

• You can use portable generators anywhere on or off your property—but never in an enclosed space. These models can quickly produce deadly levels of carbon monoxide. Always run a portable generator at least 20 feet away from your home, as well as equipment such as a central AC condenser or window AC, and direct the exhaust away from your home or any other structure, including the neighbors' home. 

• If it's raining, shield your generator with a canopy designed for your particular model.

• Several of these models offer electric starting. The battery required for electric start, however, may not be included.

• Models we test provide from 3,000 to 8,500 watts.

Typical cost:
$400 to $2,500

Portable Generators Ratings
An inverter generator.

Inverter Generators

• Because their engines are more complex, these models generally cost more than traditional portable generators of a comparable output. 

• Inverter generators are much quieter than their conventional counterparts because they throttle up and down to match demand rather than run at full power all the time. They also have more sophisticated exhaust systems which also help tamp down noise.

• They run more efficiently and produce fewer emissions, but you should still follow all the same safety precautions you would with a portable generator. 

• Models we test provide from 1,500 to 6,500 watts. 

Typical cost:
$300 to $4,000

Inverter Generators Ratings
A portable power station.

Portable Power Stations

• These devices don’t use gas or propane—they're powered by a battery that you can charge by plugging into an electrical outlet or, sometimes, an included solar panel (you might also see them called "solar generators").

• Portable power stations are relatively new to the market, and they typically cost more than portable gas generators.

• For those concerned about noise, note that these devices are extremely quiet, as they have no engine. 

• They don’t produce fuel emissions/carbon monoxide, so you can use them indoors.

• Don't expect to power as many appliances or run them for an extended period of time, since they don't output as much power as portable generators and you can't keep them running without recharging them, either with electricity or solar power.

• There are no issues with starting because there's nothing to start—think of these power stations as a large battery pack for your cell phone.

• Models we test provide from 1,200 to 1,500 watts. 

Typical cost:
$750 to $3,000

Portable Power Stations Ratings

New Safety Technology for Portable Generators

To reduce the risk of carbon monoxide poisoning, many new generators feature a built-in sensor that triggers an automatic shutoff if CO builds up to dangerous levels in an enclosed space, and some also have engines that emit less CO in the first place. Recent test data from CR shows that these safety features will likely save lives.

Consumer Reports only recommends portable generators that pass our newly expanded new CO safety technology test.

Even if your generator has these potentially life-saving features, we still advise consumers follow our longstanding safety guidelines: Always operate a generator a minimum of 20 feet from your home, with the exhaust directed away from any windows, doors, air conditioners or other structures. 

How CR Tests Generators

To test generators for performance, our expert engineers load up each model with a variety of essentials you might want to power during an outage, like a space heater, refrigerator, or window air conditioner. We make sure the generator can handle the load it promises and also determine what happens when a sudden spike in voltage hits, like what would happen if the compressor in your refrigerator kicked on when the generator was already close to capacity. The best models take that in stride, while others bog down or even stall. We also look at how easy it is to move and use a generator, as well as how efficiently it uses gasoline and how long it runs on a single tank.

Consumer Reports runs each generator through a variety of scenarios designed to capture the ways in which a consumer might inadvertently misuse a generator in their own home. We conduct these tests in a custom-built vessel on the grounds of our Yonkers, N.Y. test facility. The vessel is wired with calibrated carbon monoxide sensors, and we record CO levels throughout the container when a generator is on, noting how quickly each generator turns off when the levels become potentially dangerous. For more details, read How Consumer Reports Tests Generators for Safety. 

Features to Consider

Don't let rain, snow, or wind keep you in the dark. Consider these options to make sure you get the best generator for your needs.

Automatic CO Shutoff
This critical safety feature automatically shuts down a generator's engine if a built-in CO sensor detects levels of the deadly gas building up to certain levels. A portable generator must have this feature and pass CR's safety tests, to earn a spot on our list of CR recommended generators. More brands than ever offer models with this technology, including heavyweights like Generac, Honda, and Ryobi. In fact, we have over a dozen generators in our ratings with a CO safety shut off. You might see marketing terms such as "CO Guard," "CO Protect," "CO Detect," "CO Shield," or "CO Sense." The way to verify whether a generator meets one of the two standards is to look for one of these references on the packaging:

• ANSI/UL2201 Certified for Carbon Monoxide Safety
• ANSI/PGMA G300 Certified Safety & Performance

Low-CO Engine
An additional safety feature brands such as Ryobi and Echo are using to guard against risk of carbon monoxide poisoning.

Automatic Start
When the power goes off, the generator goes on—without you lifting a finger. This is great if you travel a lot or work far from home, and can't always get there quickly in an emergency.

Electric Start
Several portable models offer this push-button alternative to the hassle of pull-starting the engine. Just factor in the added cost (around $50) if the battery is not included. Stationary models have automatic starting.

Alternative Fuel Capacity
Most portable models run only on gasoline, though some come equipped to run on a propane tank or natural-gas line and others can be converted with kits.

Fuel Gauge
Especially during long blackouts, you may appreciate the ability to check at a glance how much fuel remains in your portable generator.

Low-Oil Shutoff
If oil falls below minimum levels, the generator shuts down to prevent engine damage. Typically a standard feature on stationary generators, it's increasingly common on portables.

Multiple Outlets
Four or more lets you best use the wattage by spreading the load, though we recommend using these only in an extreme pinch at home, or for when you're away at a campsite. See the next section on transfer switches.

Removable Console
This connects to the generator so you can plug in appliances without running (potentially risky) extension cords outdoors.

Yes, You Need a Transfer Switch

What's that? The short answer: It safely connects a home standby or portable generator to your circuit panel via one cable. Skipping it could endanger utility workers, cause appliances to fry, and damage your home's wiring, not to mention the generator itself.

We recommend that you have a licensed electrician install it, and you should be prepared to pay from $500 to $900 with labor. With a stationary model, the transfer switch turns on automatically. For portable models, you'll need to flip a few switches by hand when the power goes out. (Be sure to have your electrician walk you through the procedure.) 

Most transfer switches are designed for a 220-volt input, which means you're looking at a generator of 5,000 watts or more. For stationary models, it shuts off when the power goes on; for a portable, you'll flip the same switches the other way to bring up live power.

Want to save money? Install an interlock device instead, which costs $100-$200 less than a transfer switch and can be installed in less time by an electrician. This covers your service panel's main cutoff switch—this covers your service panel's main cutoff switch—so you can only power your home from one source.

A portable generator hooked up to an electrical panel via a transfer switch.
Illustration: Chris Philpot

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