Dear Jim: We already have a big-screen television and my children want a home theater sound system. I saw some rated at 600 and 800 watts which would be expensive to operate. How do I go about selecting one? – Kath N.

Dear Kath: With both a big-screen high-definition television and a surround sound home theater system running, it can draw quite a bit of electricity, but not as much as you might think. The size of the television is not a good indicator of its operating costs. Its design type is more important.

The wattage rating you see on the packaging for a home theater system is the sum of the sound output from the speakers. A system that has six 100-watts speakers will be listed as a 600-watt system. If you look at the main power supply specifications, some may actually draw as little as 200 watts of electricity to produce that much sound. A powered subwoofer speaker will use a little more.

At an electric rate of nine cents per kilowatt-hour, installing a surround sound home theater system which uses 200 watts will cost about two cents per hour it is used. It is also wise to switch off the power when the movie is over to save a little more electricity from the sound system.

Since the cost to operate one is relatively low, most experts recommend buying the most powerful system (speaker wattage) you can afford, up to about 100-watts per channel. Above this, your children may crank it up and literally drive you out of the house. Higher wattage speakers on a low setting generally have less sound distortion than lower-wattage ones turned up.

There are several different sound formats you can select for your home theater. Dolby digital is most commonly used on DVD movies. It offers five distinct channels of sound plus a subwoofer for low frequency effects. The subwoofer is a large speaker that makes you actually feel a train go by.

Standard Dolby digital is often referred to as “5.1” for the five speakers and one subwoofer. A receiver (tuner/amplifier) control unit decodes audio information on the DVD movie into the five-plus-one channels of sound. The next step up is Dolby Digital EX which is 6.1 with an extra rear speaker. A competing sound format is DTS, but not as many DVDs and games use this.

Unless you understand audio equipment, it is best to buy a “home theater in a box.” These are complete systems which include all the matched speakers, color-coded wiring and a receiver control unit. The most difficult part of installing one is trying to hide the wires leading to the rear speakers.

If you want to select individual components to make a system, make sure to purchase matching speakers of the same output wattage for the most true sound. You may consider getting wireless rear speakers to simplify installation.

The following companies offer home theaters in a box: JVC (800-252-5722 www.jvc.com), Onkyo (800-229-1687 www.onkyousa.com), Philips (800-531-0039 www.philips.com), Samsung (800-726-7864 www.samsung.com), Sony (800-222-7669 www.sony.com), and Yamaha (800-492-6242 www.yamaha.com)

Send inquiries to James Dulley, 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit www.dulley.com.