When the grid goes down, it may be time to shop for a whole-house generator.

The Installation Estimate for a Whole-House Generator

by Kelvin O'Donahue

Folks who have endured long power outages caused by storms often look into installing a whole-house generator. Unlike the gasoline-powered generators found in hardware stores, a whole-house generator is a permanent installation connected to an external fuel source and wired directly into the home's electrical system. Some such generators are standby power sources that automatically turn on when a power outage begins and off when power is restored. Installing a whole-house generator can be expensive because it requires expertise beyond that of even advanced do-it-yourselfers.

1. Generator

The heart of the system, and the most expensive item, is the generator itself. Generators are rated by their maximum output in kilowatts (watts times 1,000), and come in a range of capacities. To determine the capacity your home needs, you need to estimate the maximum wattage drawn at any given time. Generator manufacturers and vendors provide calculators and tables so that buyers can estimate their needs. Whatever the capacity of the generator, expect to spend at least several thousand dollars, depending on the generator's features and capacity. When selecting a generator, consider both the generator's capacity and fuel source. In cities and suburbs, most homes have access to natural gas lines. In rural settings, a standby generator can be run from propane, diesel or gasoline, all of which require installation of a fuel tank. If continuous power is critical, consider a dual-fuel generator that can run on a different fuel if the natural gas supply is interrupted.

2. Pad

A standby generator is a large, heavy object. Because of its size and weight, a generator must be installed on a stable surface such as a concrete pad. A competent do-it-yourselfer can install a pad, given the required dimensions and a schematic of required anchor bolts or other fittings. A generator vendor can also typically build a pad or contract with a third party to do so as part of the installation. The pad is an added cost above the base price of the generating unit.

3. Siting

The ideal situation is to install a generator that is immediately adjacent to the house's electric meter and gas meter, making the distance required to make the necessary hookups shorter. It is also desirable to locate the generator where it is out of sight and the operating noise level is not intrusive. The installer must dig trenches for a line to the fuel source and a line to the electrical main, which requires that possible obstructions, including sprinkler system piping, be located. Long trenches cost more than short ones, and trench cost increases with depth. Some buyers will also want a fence or other shield to hide the generator and any associated fuel tanks. All these costs are also added to the base price of the generator.

4. Fuel Hookup

Whole-house generators use fuels such as natural gas or diesel to generate electricity. If the generator will be connected to the household natural gas supply, a contractor will need to add a wye or tee connection between house and meter and run a supply line to the generator. A generator powered by propane, diesel or gasoline requires a line to the fuel tank. Local building codes mandate the required line and fittings materials and the depth of burial of supply lines. The installation of supply lines, including trenching and fittings, is also over and above the cost of the generator.

5. Electrical Hookup

The job of a standby generator starts when power is interrupted and ends when power is restored. When the generator is running, the house must be isolated from the power grid. This isolation prevents the release of power into the grid both as a matter of economics and of safety. The device that performs this function is the transfer switch. Both manual and automatic transfer switches are available. An automatic switch includes circuitry that senses a power outage and starts the generator. A manual switch requires that someone turn the system on by hand. A transfer switch is required and, in many areas, must be installed by a certified electrician. Expect to pay an additional several hundred dollars for the switch and more for installation. In addition, the generator must be connected to the house with a supply line that, depending on location of the generator, may be buried. Supply line installation and hookup is an additional cost.

Photo Credits

  • Digital Vision./Photodisc/Getty Images