Five Tips for Buying Backup Power
| Download our worksheet (PDF) to help you determine your power requirements. |
What Types of Generators Are There?
Generators come in two basic types: standby and portable. There also are inverters, which are not generators but may meet your needs. The source of backup power you ultimately choose will be determined by many factors, including your power requirements.
A standby generator is installed permanently outside your home or commercial building. |
Portable generators, such as this Briggs & Stratton model, are fueled by gasoline and include 120-volt power outlets like the ones in the walls of your home. |
View a movie about why you might want to consider installing a standby generator (requires Flash). |
Standby Generators: A standby generator is permanently installed outside your home or commercial building and wired directly into the electrical system to provide power to some or all of your home's circuits during a disruption of normal utility power. Standby generators are fueled by liquid propane or natural gas.
The number of circuits to which a standby generator can provide power--and the number of appliances you can run on those circuits--is determined by the power capacity of the generator.
Standby generators are about the same size as, and look similar to, a standard central air conditioner. A standby model may cost as little as $1,500 or as much as $15,000 or more--the greater the power capacity, the higher the cost.
Portable Generators: Portable generators are versatile. You can use them for
- emergency power at home,
- for power in remote locations where utility power is unavailable, or
- for recreational purposes, like boating or camping.
Portable generators are fueled by gasoline and include 120-volt power outlets like the ones in the walls of your home. When the generator is running, you can plug appliances and tools directly into these outlets. Some generators also include 240-volt outlets (that is, the kind of outlet for an electric dryer or for other large appliances). Portable generators range in cost between a few hundred dollars to several thousand dollars depending on the capacity and features.
Inverters: Inverters turn DC power into AC power, the type of current that powers everyday appliances. A common use of an inverter is to connect one into a car's cigarette lighter and then plug small home appliances into the inverter.
Inverters have added features over the years, and today many inverters include emergency radios, lights, or their own internal battery to store power.
When you purchase an inverter, you need one that can handle the wattage of the appliances you intend to connect to it. Some inverters are made specifically to power low-wattage appliances, like portable phones or digital music players. Others can handle heavy-duty power tools.
If you're buying an inverter that's powered by its own battery, you'll have to consider how many hours the inverter can provide power before needing a recharge.
The rest of this buying guide focuses solely on standby and portable generators.
How Much Power Do I Need?
There are two basic power measurements for generators: peak power (also known as startup power) and continuous power. Both are measured in wattage.
- Peak power is the wattage required for appliances at startup or when they are running at their highest levels of power consumption.
- Continuous power is the wattage required for operation of those appliances under normal load.
We've provided a worksheet to help you determine your specific needs based on the peak and continuous wattage requirements of the appliances you want to power. What's below is a general guide. Standby Generators: Standby generators create from 5,000 to 25,000 watts or more of power. You'll have to choose a generator that supplies sufficient peak and continuous wattage for the appliances on the circuits you need to power.
You can choose between an air-cooled and a liquid-cooled model standby generator. Generally, liquid-cooled models are bigger and create more power.
Portable Generators: A small 1,000-watt portable generator may be all you need for recreational purposes. And you may use up to 8,000 watts if using a generator to power tools on the jobsite.
Because you plug appliances directly into a portable generator, you'll also want to make sure that your model has the number and type of outlets you need. The size of the fuel tank also is crucial. The bigger the tank, the longer your generator can run without refilling and produce power.
If you want to use a portable generator to power specific circuits in your house--or the whole house--follow the guidelines for choosing a standby generator.
What Features and Accessories Do I Need?
Aside from pure power production, there are some useful features and accessories to consider when buying a generator.
Transfer switch: If you want to use your generator to power your home, you'll need a sufficiently sized generator and a transfer switch. The transfer switch safely closes off the utility power line to your house's electrical system and opens a direct line to the generator and reverses the process when utility power is restored.
Standby models can work either with a manual or an automatic transfer switch. The benefit of an automatic transfer switch is that it senses when utility power has been lost and automatically switches to generator power.
Wheeled Frames: As the name suggests, portable generators can be transported to different locations. The smallest portable generators are comparatively light--perhaps 50 pounds--and can be carried. Larger models can weigh as much as several hundred pounds, making a wheeled frame essential for transportation.
Other Considerations:
- Noise: Generators aren't necessarily quiet. Some offer extra features to reduce the noise created during operation.
- Weather Protection: Make sure the generator you purchase is suited for the climate in which you'll use it.
How Do I Install and Operate a Generator?
Standby generators are wired directly into your current electrical system and generally require professional installation. View larger. |
Setup for portable generators is easy. Just make sure to keep the exhaust port pointed away from your house, and to have the proper distance from your windows and other house openings. View larger. |
Standby Generators: Installing a standby generator by yourself may void the unit's warranty or violate local building codes, so research these issues before you begin. The basic steps are as follows. First, mount the unit outside your home on a concrete pad or plastic mounting pads that come with the generator. You may need a contractor to pour the concrete foundation and mount the generator.
Next you'll need to contact your gas or propane company to connect the unit to its fuel source.
Last, you'll have to call an electrician to hook the generator up to your home's electrical system. Some generators come with pre-wired kits that make it easier for the "do-it-yourselfer" to do the wiring. In most cases, it's probably safest and best to have this work done for you.
Once installed, operation depends on whether you've used a manual or an automatic transfer switch. With an automatic transfer switch, if the generator senses a disruption in utility power, it turns itself on and takes over power production until utility power resumes. With a manual transfer switch, you have to handle these chores yourself.
On a standby model, you'll have to change the oil and filters on a regular basis. Many manufacturers provide maintenance kits to make this easier.
Portable Generators: If you're not planning to hook your portable generator into your home or building's electrical system, there is not a lot of setup involved other than finding a safe place outside your home for the generator. Because portable generators create carbon monoxide, you should never run them inside a building, beneath a window, or near any opening to your house (doors, vents, etc.).
Once situated, fill the generator with the required type of gasoline and oil and start the unit. Startup can be as simple as pressing a switch, but on some you'll have to yank a manual recoil pull-cord.
Of course, you will have to plug the appliances you want to power into the generator, refuel it as necessary, and shut the generator off when you're finished with it.
If you want to connect your generator to your home's electrical system, you'll need a manual transfer switch. Make sure your generator's manufacturer supports connecting your model to a transfer switch. If supported, comply with your model's safety and warranty guidelines as well any local building codes during the installation. In general, it's best to hire an electrician to handle the wiring of your home to the generator and transfer switch.
However you use your generator, over time you'll have to change filters, oil, and spark plugs. Plus, you should not store raw gasoline in the generator when you're not using it. Either run the generator empty or add a gasoline stabilizer that will prevent the gasoline from "gumming" up. Many manufacturers sell tune-up kits for their models.
How Do I Run a Generator Safely?
- Do not operate generators indoors, in enclosed spaces, or near a window. Make sure there is proper ventilation for all exhaust.
- Follow the manufacturer's instructions for installation, operation, and maintenance.
- Do not operate generators near combustible materials.
- Operate portable generators on a level surface.
- Do not plug a portable generator directly into your house circuit.
- Do not attach a generator's transfer switch to your circuit box yourself unless you're very sure of what you're doing. Check all applicable local, state, and national codes and the warranty information before you do this.
