On most occasions, power outages are only a temporary nuisance. A violent thunderstorm or howling blizzard blows through, the lights blink off, but electricity is usually restored within a day.

If the weather is particularly bad, though, it may take much longer for utility crews to repair the lines. Or perhaps you live in an area where outages are more frequent due to falling trees or other hazards.

During these situations, the lack of electricity becomes much more noticeable. Food is more likely to spoil, flooding may occur when a sump pump stops working, and pipes can freeze when the furnace fails to heat the home. You'll also suffer the comparatively less pressing inconveniences of not being able to charge your phone or watch TV.

To avoid the problems of a prolonged power loss, you can invest in a generator at your home. Portable generators allow you to keep some appliances running, while permanent standby generators will automatically kick in when your main source of electricity fails.

Finding the right size

A generator is only useful if it can provide electricity to the devices you plan on using during a power outage. The American Red Cross says you risk blowing a fuse or damaging equipment if you draw more power than the generator can produce.

For this reason, it is important to make sure the generator is adequately sized for your home. One option is to have an electrician visit your home and determine how much electricity you use. You can also tour your home to do the calculations on your own.

Some generator manufacturers will offer online calculators to help you determine your energy needs. Fran Donegan, writing for Realty Times, says these tools will ask you for your home's square footage as well as the appliances in the residence.

Family Handyman Magazine says your tally should include any devices you want to run during a power outage. You can consider excluding some devices, such as the air conditioning, if you can go without them for a few days; otherwise, you'll have to invest in a more powerful generator.

Keep an inventory of each device and its wattage. There should be a label providing this information, though you may have to pull the appliance away from a wall to check the back. If the amperage is listed rather than the wattage, multiply the amps by the volts to get the correct number. Make a cumulative total for the home's lights, and don't forget to include essential things like the refrigerator or electric water heater.

The generator's capacity needs to be higher than the combined wattage of these items. Roy Berendsohn, writing for Popular Mechanics, says you'll also need to add the startup wattage of the largest motor in the home, such as the furnace fan.

Family Handyman suggests multiplying the combined wattage by 1.5 to determine an adequate size for the generator. Double-check your numbers, and consult with an electrician or the generator dealer to see if they dispute the figure.

Portable generators

A portable generator is the most inexpensive option for keeping your home powered during an electricity outage. Once this generator is rolled out onto your yard and fired up, you can run extension cords from it to plug into specific items.

Portable generators are usually quite heavy, so most will come with wheels to help you move it into place. Some models have a pull start, while others have an ignition key to get them going.

If you don't want to have extension cords running throughout the home during a power outage, you can connect the generator to a transfer switch instead. This switch, located as a subpanel off the main circuit panel, allows the generator to provide electricity to circuits rather than individual appliances. Since it's a complex job, you should leave the transfer switch's installation to a professional.

You can specify which circuits get power when the transfer switch is flipped, allowing you to use a variety of items without overwhelming the generator. If you need to use most or all of your electric items, you'll want to make sure the generator has a high wattage.

Berendsohn says homeowners can test a portable generator to make sure it will work during a power outage. Unplug the devices you'd like to run, start the generator, and see if it can adequately power the selected items.

The main drawback of a portable generator is the lengthy process of setting it up. A homeowner needs to bring the generator outside, start it up, and connect the devices in order to provide electricity to the home.

Another limitation is the number of items you'll be able to run using the generator. Family Handyman says portable generators often allow you to plug in only two to four cords. And if you aren't using a transfer switch, you'll have to watch out for the extension cords snaking through your home.

Portable generators rely on fuel to generate power, so you'll want to see how long it can run on a single tank. You'll have to shut off the generator and let it cool down before refueling, and it may run out of gas during the night if it has poor efficiency or a small fuel tank. Adding a fuel stabilizer to the gasoline will help prevent it from breaking down while the generator is being stored.

Some portable generators may be very noisy. Nearby neighbors are sure to be annoyed by the sound of a loud generator running through the night. If other properties are located close to yours, or if your neighborhood is subject to a noise ordinance, you should look for a model with a low decibel level.

Standby generators

Unlike portable generators, standby generators are permanently installed outside the home. Donegan says these systems have a transfer switch, which is tripped when the main power source goes out. The switch disconnects the home from the power grid and activates the generator to restore electricity. Once utility crews get the main power back online, the transfer switch shuts off the generator and reconnects the home to the main grid.

Several different fuels can be used to run a standby generator. Berendsohn says they may use propane, natural gas, gasoline, or diesel. Donegan says you may be able to connect the generator to a gas line to ensure that it doesn't run out of fuel.

Standby generators may have features allowing them to manage the electricity needs of a home. Power management modules can prevent overloading by shutting down power to certain parts of the home. Some models may allow you to remotely monitor the generator.

The main advantage to a standby generator is its convenience. When the electricity goes out, the generator will restore power automatically. You won't have to set up and disconnect the generator for each power outage.

In addition, standby generators are often designed to power the entire home rather than certain parts of it. Whole-house generators are available starting at 6,000 watts, and other models can provide 30,000 watts or more to the home.

This convenience comes at a cost, however. You'll need to get a professional to install both the generator and the transfer switch subpanel, and these services will easily run up a bill of thousands of dollars. The installation of a standby generator also requires you to get a building permit, comply with any setback rules, and possibly install a concrete pad and underground cables for the system.

Like portable generators, some types of standby generators will produce a lot of noise when they are active. If noise is a concern, you should consider air-cooled models or other quiet generators.

Battery-inverter generators are one quiet option that can be installed inside the home. Berendsohn says these systems are simple and do not give off exhaust, although they do need to be ventilated since the batteries can produce fumes.

However, battery-inverter systems also produce a relatively low amount of power unless you install several batteries. These systems are best for homes with low wattage requirements or for providing power during brief outages.

Safety

Since generators involve fuel and electricity, it is essential to run them safely. Improper use of a generator can be deadly for both the people within a home and utility workers.

With portable generators, the main concern is the production of carbon monoxide. The generator should be located at least 10 feet from the home to keep any fumes from entering.

The American Red Cross says portable generators should not be located in any enclosed or partially enclosed space, even if it is ventilated. Keep the generator away from any doors, windows, vents, or other openings.

Make sure your carbon monoxide detector is functioning. If you notice symptoms of carbon monoxide poisoning while using the generator, such as dizziness or weakness, leave the home immediately.

Any extension cords you plug into the generator should be rated for outdoor use and capable of carrying an electrical load at least equal to that required by the appliance it is powering. Make sure the cords are not frayed or otherwise damaged. Berendsohn says you should only use three-pronged cords, since older two-pronged ones might cause electrocution or a fire hazard.

Never connect a generator directly to a wall outlet. Not only will this bypass the protective measures in your home's electrical system, it will also back-feed electricity through the circuit breaker and into the power lines. This process can prove fatal to utility workers.

When refueling the generator, let it cool down before adding any new fuel. If the generator is still hot, it may ignite spilled fuel. You should also make sure fuel is stored in a proper container and kept away from any ignition sources.