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Backup Power for the Conventional Home
Introduction
In the past, most of our business has been with people powering off-grid homes. Recently more and more people have begun to consider an alternative power supply for their homes in case of power grid failure. Supplying backup power for a home tied to the power lines is an entirely different problem than supplying primary power for an alternative energy home. In the next few pages we will try to describe how to provide emergency power for the necessary items in your home--usually central heat, refrigeration, water pumping and lighting.
Solar Power/Wind Power
Many people hope that solar panels or a wind turbine can provide backup power for their homes. They are crestfallen when we tell them that this probably won't work for them. A typical home connected to the power lines consumes about 25 kilowatt hours per day on average. This does not include electric power for hot water, space heating or air conditioning. Making 25 kW-hrs of electricity per day is nearly impossible using alternative energy methods. In the northern latitudes $6500 worth of solar panels produce 6 kW-hrs a day, on average in the summer and only 3 kW-hrs a day in the winter. That's little more than one-tenth the power required for an average American home. A normal refrigerator uses roughly 2kW-hrs a day. A central heating system may use as much as 3 kW-hrs a day just for pumps and motors.
An alternative energy home is designed to use only a small amount of electricity. Cooking, hot water heating and space heating all utilize some form of energy other than electricity. In the northern latitudes most people must use a gas refrigerator. Once these major electrical loads are shifted to another energy source, the remaining necessary electrical loads are made as efficient as possible. Compact fluorescent lighting is used throughout the home. A water pump is sized just large enough to do the job. Appliances are chosen for their frugal use of electricity. Nothing is left on when not being used. Appliances with phantom loads such as TV cathode heaters and digital clocks are placed on switched outlets. With a little extra effort one can actually live quite comfortably on alternative energy.
Alternative Power for the Conventional Home
Unfortunately most homes in the U.S. are not designed with frugal electrical use in mind. So how does the homeowner provide an alternative power source for a conventional American home when the grid fails? The first step is to decide which items need to be powered when the power grid fails. In limited situations solar modules may be used, i.e. to run a water pump and some lighting. Some may even want to add a freezer, TV, and a computer. (Keep in mind electric heat, electric hot water and air conditioning are really not possible for an affordable backup power system to deal with. One could buy a very large generator and run it 24 hours a day, but this isn't really practical unless you have unlimited means.)
The only practical way to provide emergency backup power is with the use of a generator and an inverter/battery system. This combination is called a Generator/Charger System. Despite its lack of "greenness" a generator is the only affordable way to produce the 4 to 8 kW-hrs a day necessary to power the essential items listed above.
Generator Selection
The first step is to pick a generator. A 4 kW to 10 kW generator should do. Fuel choice is the next variable. Gasoline generators are the least expensive and probably the easiest to procure. They are usually portable and easy to move. But gasoline has its drawbacks. It may not always be available when you need it. Additionally, storage of gasoline is difficult and dangerous.
LP gas (propane) or diesel generators perform well in a home backup situation, but they are much more expensive than portable gasoline generators. Commercial grade (1800 rpm) generators will last much longer than a gas generator. They can be remotely started and they can usually be configured for full 120 volt output, a benefit when used in conjunction with an inverter. Fuel can be stored in underground tanks in the case of LP gas or in large above ground tanks for either fuel.
We recommend a small portable gasoline generator for our alternative energy customers who are living mainly on solar and/or wind power. They will probably need it only a few times each winter and can easily move it to different locations for other uses during the year. This type of generator is a good choice for alternative power for the home as long as it is sized large enough to power the necessary loads.
For our customers who run businesses in their homes which would use more energy than the typical household, we usually recommend commercial grade LP gas or diesel generators for their longevity. Likewise, those homeowners who want to power relatively large loads during power outages may want to consider a larger, commercial grade generator, especially if cost is not the main factor.
Generator Selection Chart
Note: Information on Backup Power is continued on the next web page.
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