UPS – Uninterruptible Power Supply
UPS devices are an alternative to fuel-powered generators. The UPS consists of a battery set (typically deep cycle lead acid 12-volt batteries), a charging system, and an inverter to convert stored DC power to AC power. The UPS most commonly has been used for computers or other electronic equipment that must not lose power at all. A UPS “senses” when power supplied by the electric utility is being lost, and then provides the energy to keep the equipment running.
WHOLE HOUSE UPS SYSTEM
Some UPS units now on the market can be sized up to perform backup for larger home systems, such as refrigerators, water pumps, furnaces and lighting. This whole-house system UPS can be controlled by circuits that monitor the status of power provided by the utility. If the power fails, the controller waits briefly (you set the time) before automatically switching over to battery storage. The delay is to avoid making the jump to backup power when the grid is just experiencing a momentary loss of power, not a full-scale interruption. The battery system remains active until power from the grid is fully returned. In the case of an unusually prolonged outage, battery power can probably sustain a house for a couple of days, depending on the electric load it is being asked to supply. If more storage is required, additional batteries can be easily added. When power returns, the device then transfers automatically back to grid power, and the charger replenishes the batteries.
A UPS could be more expensive to buy than a generator, but less expensive and easier to operate and maintain. Plus, the convenience of having no moving parts, the ability to provide backup power without any owner action, and the absence of noise and combustion pollution, may give significant advantage to whole house UPS compared to generators.
Following is an example of the cost to purchase a UPS versus a generator:
UPS: see Xantrex.com: Use the product name shown, and then go to a source such as Amazon.com to purchase or read more information.
Generator: A 2,500-watt, 5.5 horsepower gas generator lists for $1,055. This unit has an electric start. This same catalog lists a transfer switch capable of up to a 5,000-watt load at $270.
Installation for both generators and whole-house battery systems by a qualified electrician would likely be similar, as both involve siting the alternative electric source where appropriate, and wiring it into the home’s electrical system and service panel.
Here’s a Currents article about a UPS wired to emergency loads in a house main service entrance: