Winter's latest wintry blast has brought several perplexing questions to Washington area consumers: How much do you really save on heating bills when you lower the home thermostat? When you set the thermostat 10 degrees lower at night while the family is sleeping? When you do both?

You could save as much as $95 a year, if you are typical, according to Washington area energy experts.

Actual savings for reduced thermostat settings vary, they say, depending on how cold it gets outside, how well the house is insulated and the efficiency of the heating equipment in your home. But generally, the lower the thermostat setting -- down to 60 degrees, anyway -- the more you tend to save.

One notable exception is the heat pump that uses electric resistance heaters for auxiliary heating. Consumers with heat pump systems shouldn't use temporary thermostat setback as a conservation step, because it can increase rather than decrease their energy use.

But if you have an average Washington area single-family detached house with a heating system other than a heat pump, here is how you save with thermostat adjustments:

* $68 a year (13 percent of the annual average heating bill of $525) when you reduce the regular themostat setting from 72 degrees to 68 degrees.

* $63 a year (12 percent) when you lower the thermostat from 72 degrees to 62 degrees for eight hours each night.

* $95 a year (18 percent) when you both reduce the setting from 72 degrees to 68 degrees and lower the thermostat to 62 degrees for eight hours each night.

These savings, which would be greater for those who live in larger-than-average homes and smaller for those who live in apartments and smaller-than-average homes, were developed by Washington Gas Light Co., which provides natural gas to heat about 60 percent of the 1.2 million households in the Washington area. The other 40 percent rely mainly on heating oil and electricity.

Consumers trying to save with thermostat setbacks can make manual adjustments each morning and each evening. But it would be more convenient to install an automatic control, which turns the heat to the setting you want at the time you want it. You can, for instance, set the automatic control to turn the heat down to 62 degrees at 11 p.m. and then back up to 68 degrees at 7 a.m.

Several variations of the automatic controls are available at Washington area hardware stores for prices ranging from $50 to $150. You may be able to install the control yourself, or you may have to have a professional do it. In either case, the control typically pays for itself in less than one year.

While thermostat reductions can save money, they can also create new problems if they are too low, according to WGL representative Tom Julia. For instance, he said:

* Many consumers are comfortable with the thermostat at 65 to 68 degrees during the day, but that can be dangerous for infants and elderly people, who need more warmth. A minimum regular setting of 70 degrees is recommended for the very young and the very old.

* Consumers risk frozen water pipes when they leave their home thermostat below 60 degrees for extended periods of cold weather.

For more information about ways to save money on energy in and around your home, request a free copy of "The Virginia Energy Book," a 69-page paperback book compiled by the Virginia Division of Energy. Virginia consumers can call the toll-free number 800-552-3831 to order a single copy. Those outside Virginia can call 804-257-6696 or write the Department of Energy, 2201 West Broad St., Richmond, Va. 23220.