Q - I try to set my furnace thermostat back at night to lower my heating bills, but I often forget. It's also cold in the morning. How should I select a programmable automatic thermostat and will it save much? R.D.

A - Setting your furnace thermostat lower is the best and least expensive method to significantly lower your heating bills. You can save from one to two percent for each degree you lower it for an eight-hour period. Since the furnace or heat pump runs less, it may require fewer repairs.A programmable thermostat can cut your summer air-conditioning costs even more. Some thermostats automatically switch to a summer time/temperature schedule when cooling is needed. A year-round savings of more than $100 is not uncommon. The cost of many programmable thermostats ranges from $50 to $100.

With a programmable thermostat, you won't have to sacrifice comfort. By programming the proper time/

temperature schedule, you hardly notice the cooler temperatures. For example, with a nighttime temperature setback, it heats up your house in the morning 30 minutes before you get out of bed.

If there are other times during the day when the temperature can be lower, the savings will be greater. For example, if everyone is gone for several hours during the day, program the thermostat to lower the temperature.

An important selection consideration is the number of daily time/temperature schedules the thermostat will accommodate. Some thermostats allow you to program a different schedule for each day of the week. This is convenient if you work just several days a week or have other regularly-scheduled activities away from your home.

Other thermostats allow you to program only one schedule for weekdays. Most programmable thermostats also allow for separate weekend schedules or even different Saturday and Sunday schedules.

A temporary override feature lets you bypass the regular schedule without reprogramming it. This is important when you stay home sick, for example. A battery-backup feature saves the program if there is a power outage. The small battery lasts a year or longer.

Most automatic thermostats are easy to install yourself. Shut off the electric power to your furnace. Unscrew the old thermostat and wires and attach the new one. Simple instructions show how to hook up the wires on the thermostat and to program the time/temperature schedules you desire.

You can write to me for UTILITY BILLS UPDATE No. 104 showing a list of 10 programmable thermostat manufacturers, number of daily time/temperature schedules available, and a chart showing the savings by installing a thermostat. Write to James Dulley, The Deseret News, 6906 Royal Green Dr., Cincinnati, OH 45244. Please include $1.00 and a self-addressed envelope.

Q - We are attaching a kit solar greenhouse to our house and we want to use the brick wall for solar heat collection and storage. Should we coat it with cement to make it smooth and what color should we paint it? I.D.

A - Flat black is always the best color to use for solar absorption, but that could ruin the rustic appearance of the brick. The dark red-brown color of the brick is only about 10 to 15 percent less effective for gaining solar heat.

You shouldn't coat the brick surface to make it smooth. The rough surface can actually increase the effective area for heat absorption. Also, the amount of heat reflected away and lost is less with the natural brick.