Affiliate Disclosure:This Old House’s Reviews Team is committed to delivering honest, objective, and independent reviews on home products and services. To support this business model, This Old House may be compensated if you purchase through links on our website.
In This Guide: Types of Generators | How Much Power Do You Need? | How To Operate a Generator Safely | What Is a Transfer Switch? | Types of Fuel | How Much Should You Spend? | Differences Between AC and DC | Other Key Features
Whether you are a homeowner preparing for potential blackouts or need to power your devices while camping, RVing or tailgating, having a generator on hand is essential. Generators help you run your most-needed devices when power is limited, and some even power the whole house.
How do you decide which is the best generator for you? The This Old House Reviews Team put together this comprehensive generator buying guide to help you make an informed purchase.
In this guide, we’ll cover what devices you can power, what fuel sources are required, the difference between a whole-home and portable generators, and more. Here are the most important things to remember when shopping for a generator.
Types of Generators
There are four main types of generators.
Home Standby Generators
A standby generator is a heavy-duty device that gives your home backup power during an electrical outage. A home standby generator is hardwired into your home. It should be installed by a professional so you can ensure it is set up in the proper location and follows local ordinances and noise restrictions. It is connected via a transfer switch and automatically kicks on when there is a power outage and turns off when it senses power has been restored.
Portable generators can be used in any open space and are ideal for bringing with you on camping, hiking, or RVing trips when you only need to power a few devices. Portable generators come in various sizes, with larger models having more power than smaller models.
Portable generators usually run on gas and are less expensive than standby generators but can power fewer items. These generators typically run on extension cords unless you purchase a manual transfer switch.
An inverter generator is a type of portable generator that adapts to the power demand placed on it by throttling up and down. It utilizes sophisticated exhaust systems to run at a low noise level and is highly fuel efficient.
A solar generator, also known as a portable power station, operates like a large battery that charges by plugging into an outlet or via solar panels. It does not use propane or gas to power on and is typically lightweight and portable. Solar generators are ideal for use in a short time period and for powering a small number of devices at once. Since they don’t have an engine, solar generators run quietly, which could be a benefit for those concerned about noise level.
How Much Power Do You Need To Operate Devices?
One of the primary considerations when buying a generator is: what do you need to power? Depending on the size of your home and the number of devices you need to power , standby generators should have the amount of power you need for most, if not all, of your home appliances. In most situations, operating a 20kw generator should be enough to power the majority of your home devices.
However, if you’re operating a portable generator, you’ll need to consider the power requirements for the devices you want to use. Larger portable generators will be able to power more devices but will be harder to move around and more difficult to maintain.
“The larger the generator, the more it weighs and the bigger it is, the more fuel it takes,” says Melanie Tydrich, a generator expert from Kohler. “Some people are going to say, well, I’m just going to get the biggest generator I possibly can and then I don’t have to worry about it. But realize, if you do that, you’re going to be burning a lot more fuel, and it’s going to take up a lot more space.”
What size generator do you need? You can calculate your power needs by using something like the chart below, which gives you a general estimate of how much wattage everyday household items like a fridge, air conditioner, and washing machine use.
Common Household Items
|Ceiling fan||65-175 watts|
|Coffee maker||600-1,200 watts|
|Desktop computer||125-200 watts|
|Portable heater||750-1,500 watts|
|Sump pump||800-1,000 watts|
|Television (42-inch)||200-300 watts|
|Toaster oven||1,000-1,200 watts|
|Vacuum cleaner||300-1,500 watts|
|Washing machine||500-1,200 watts|
|Water heater||4,000-5,000 watts|
|Well pump||750-1,000 watts|
|Window air conditioner||400-1,200 watts|
How To Operate a Generator Safely
While generators are useful, they are also potentially dangerous if proper precautions aren’t taken. Here are some safety tips to keep in mind to use a generator safely.
- Read the instructions from the owner’s manual carefully when operating a portable generator. Familiarize yourself with how to operate the generator before you need it so you’re completely prepared when the time comes.
- Use a fuel stabilizer when storing gas for an extended time period. Unstabilized gas can become a fire hazard.
- Avoid refilling your generator when it’s hot or near warm objects to ensure you’re operating it safely.
- Connect your generator to a transfer switch to reduce the risk of getting electrocuted or damaging your appliances. When in doubt, call an electrician to apply the transfer switch for you.
- Keep your generator at least five feet away from surrounding surfaces. This can help reduce the risk of overheating the items and causing them to catch fire.
- Never operate a gas generator in an enclosed area. This can lead to a buildup of carbon monoxide, which could be potentially lethal. Make sure you’re always operating your generator at least 20 feet from your home.
“If you’re running a portable generator, you’re going to have to take it out of storage, put it in place somewhere safe outside, away from intake vents and not on a screened-in porch,” says Tydrich. “Take that carbon monoxide seriously. […]Have a carbon monoxide detector in the home so if all else fails, at least you’ve got another backup. People don’t realize that it’s an undetectable gas until it’s too late.”
What Is a Transfer Switch?
Transfer switches safely connect your generator to a circuit panel via a cable and allow you to “switch” between grid power and generator power.
Automatic transfer switches come installed in standby generators and automatically switch between grid and generator power when they detect a blackout. Manual switches require you to switch over the power at the electrical panel yourself.
Without a transfer switch, portable generators need to run on extension cords, which can be hazardous and difficult to set up. Operating a generator with an extension cord means you can only operate devices running through an electrical outlet, not other units such as overhead lights or sump pumps. If you do run extension cords, you’ll need to ensure they are properly rated for the current they will be carrying.
In the video below, Ask This Old House master electrician Scott Caron shows how to install a transfer switch for a portable generator:
Types of Fuel Used in Generators
Generators can run on gasoline, propane, natural gas, or solar energy.
Gasoline-fueled generators are the most common fuel source in a portable generator. When running a gas generator, it’s important to ensure you are prepared with gas ahead of time while also keeping in mind that it has a shelf life.
“During an outage, a lot of gas stations either don’t have gasoline, or they have really long lines,” cautions Tydrich. “If you’re going to store gasoline, you need to realize it has a shelf life. You need it to be fresh gasoline, and you’re going to need to go out and refuel it periodically.”
Propane is a clean fuel-burning source commonly used in standby generators. Some portable generators also use propane as a backup fuel source or connect through a propane tank. Propane is an affordable fuel option but is less efficient and powerful than other fuel sources.
Diesel is another popular option for portable generators and can be stored for a longer period than gasoline. Diesel fuel also presents a lower fire hazard than gas, but it is used more often in industrial-style generators.
Natural gas is exclusively used in standby generators and is a self-feeding fuel tied into a home’s natural gas line. The benefit of natural gas is that it can provide a nearly limitless fuel source, which means you don’t have to worry about running out of gas, diesel, or propane. However, it is less energy-efficient than other fuel types.
Solar generators use energy from the sun to back up your home via solar panels should you experience a power outage. Solar energy is completely free, clean, and energy-efficient, but if you’re planning on operating a solar generator, you should have a backup generator in place if needed. A battery backup like a power reserve can store energy and provide power to your home when in the event you can’t generate solar energy. You can also switch back and forth between solar power and another power source to help save energy and reduce energy costs.
How Much Should You Spend on a Generator?
The price point of a generator depends largely on what type you’re focusing on. Start with determining how much power you need and if you will be investing in a standby generator, or purchasing a portable generator, inverter, or solar generator.
If using a standby generator, you need to factor in installation costs in addition to the cost of a product. Your price may vary greatly depending on your property, and it’s best to consult with an expert beforehand to get an accurate estimate. New construction that can run a standby generator in an ideal location may have a much lower cost of in the ballpark of $3,000. However, some homes have complications that could increase the cost significantly.
Tydich explained some of the main t factors that could increase the cost of installing a generator. “If you’re in a situation where there’s nowhere safe to place the generator near the home because you either have windows that people open, air intakes, or other kinds of complications,” said Tydich, “you may be running pipe and conduit to the other side of the property; there may be electrical updates that need to take place, or you may not have natural gas or propane. The cost can really vary by thousands of dollars.”
Portable generators have a fixed price that depends largely on how much power the unit has and the type of fuel source. Portable generators can cost anywhere from a couple hundred dollars to upwards of $2,500 for higher-end models.
Differences Between an AC Generator and a DC Generator
When shopping for generators, you may notice some listed as AC powered and others as DC powered. AC stands for “alternating current,” and AC units will be the most popular model among household appliances. DC, which stands for “direct current,” is used more often in battery banks and backup units. If using a DC generator, you will need to convert it to AC to be able to have usable power.
Other Key Features To Look for in a Generator
Performance, type, fuel source, and safety features are the most important factors when buying a generator, but many models also come with additional features that help them stand out. Here are some extra features you can look out for when choosing between the generators on the market.
Automatic CO Shutoff
Some generators come with automatic carbon monoxide shut off if they detect certain gas levels that could be fatal. This feature is common in most newer portable generator models, giving you peace of mind while operating the unit.
Many portable generators come with an electric start feature, which means the generator can turn on via a switch, remote, or push-button instead of using a pull-cord.
Some generators come with low-oil shutoff, which means they automatically shut off when the oil reaches below a certain level. Keep an eye out for when your generator’s oil and filter need to be changed. If you aren’t comfortable changing it yourself, it’s always best to call in a professional.
A fuel gauge allows you to easily track the fuel level and see when the fuel tank is getting close to running out. You will only need this feature if operating a gas- or diesel-powered generator.
The noise level of a generator may be a factor if running it outside your home or campsite. Quieter generators run around 50-60 decibels, while louder generators can run as high as 90-100 decibels.
More Generator Resources
- Best Home Generators
- Best Portable Generators
- Best Solar Generators
- Best Inverter Generator
- Power On Demand: How It Works
- How to Install an Automatic Standby Generator
- How To Wire a Portable Generator
- How To Install a Transfer Switch for a Portable Generator
- How To Provide Backup Power without Gas
- 14 Supplies to Prepare for a Blizzard
To share feedback or ask a question about this article, send a note to our Reviews team at firstname.lastname@example.org.