If you're wondering just how much your neighborhood Clark Griswold is paying to brighten the town with Christmas lights visible from outer space, the answer varies significantly from one part of the country to another.

In Knoxville, Tenn., for example, a display on the order of Griswold's in "National Lampoon's Christmas Vacation" -- 100 strings each with 100 miniature lights (41 watts per string), one 100-watt Santa figure and a 450-watt set of floodlights illuminating a nativity scene -- would generate added costs of $63. That's assuming the lights (totaling 4,650 watts) are left on seven hours per day for 30 days.

A New Yorker with the same display would be paying an extra $136 to spread holiday cheer, while a jolly homeowner in Hawaii would see an extra $160 on his or her electric bill. At the other end of the spectrum, a homeowner in Seattle would be paying just $50 for the same display, while a homeowner in Idaho Falls would be paying just an extra $53.

Whatever the added expense, homeowners can offset most or all of the additional cost of a light display with some simple energy-saving techniques in other areas of their home that will provide year-round cost savings.

Research within the Buildings Technology Center of the Department of Energy's Oak Ridge National Laboratory has demonstrated a variety of ways homeowners can save money on energy bills.

"There are several simple and low-cost measures that a homeowner can take to realize anywhere from $10 to several hundred dollars of savings per year," said Mike Gettings, a researcher in the laboratory's Engineering Science and Technology Division.

Looking at electricity rates around the nation, the highest are in Alaska and Hawaii, where residents pay an average of 14.42 cents per killowatt hour, while the lowest rates are in the East South Central, which is made up of Alabama, Kentucky, Mississippi and Tennessee. There, the average rate is 6.43 cents per killowatt hour.

A more modest light display of 10 strings of 100 miniature lights and one 100-watt lighted Santa (510 watts total) in various parts of the country would cost as follows, listed by highest prices to lowest prices:

Pacific Noncontiguous (Alaska and Hawaii): $29 (14.42 cents per kwh);
Middle Atlantic (New Jersey, New York and Pennsylvania): $22.96 (11.39 cents per kwh);
New England (Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island and Vermont): $22.52 (11.17 cents per kwh);
Pacific Contiguous (California, Oregon and Washington): $17.60 (8.73 cents per kwh);
East North Central (Illinois, Indiana, Michigan, Ohio and Wisconsin): $16.57 (8.22 cents per kwh);
West South Central (Arkansas, Louisiana, Oklahoma and Texas): $15.66 (7.77 cents per kwh);
South Atlantic (Delaware, District of Colombia, Florida, Georgia, Maryland, North Carolina, South Carolina, Virginia and West Virginia): $15.52 (7.7 cents per kwh);
West North Central (Iowa, Kansas, Minnesota, Missouri, Nebraska, North Dakota and South Dakota): $14.82 (7.35 cents per kwh);
East South Central (Alabama, Kentucky, Mississippi and Tennessee): $12.96; (6.43 cents per kwh); and
Mountain (Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, Utah and Wyoming): $14.96 (7.42 cents per kwh).

Moving indoors, in Knoxville, for example, the cost of lighting a Christmas tree with six strings of 100 minilights (41 watts per string) would be about $3.35 for the month. In New York, that cost would be $7.21.

Researchers have found that a homeowner can reduce his or her energy bill by as much as $50 per year simply by turning the water heater setting down to 120 degrees Fahrenheit. Or, when it's time to replace the water heater, installing a residential heat pump water heater is an option that will pay the homeowner back with lower monthly bills in less than three years.

Another way to save money on energy bills, and one with less initial cost than a heat pump water heater, is to add air sealing around windows and doors, which can save up to $135 per year in the Northeast, $119 in the Midwest, $38 in the West and $74 in the South.

Other cost-saving measures with initial costs ranging from just a few dollars to a few hundred include adding attic insulation, installing a programmable thermostat for heating systems, installing low-flow shower heads, installing wall insulation and replacing incandescent light bulbs with more efficient fluorescent bulbs.