Heating A Water Bed Can Be A Real Drain On Your Energy Bill

HOME CLINIC: I'm considering buying a water bed. I've heard they use a lot of electricity to keep warm. Are there any models that are more efficient than others? And is there anything I can do to reduce the cost to heat it?

- K.M., Kent

DEAR K.M.: This is a very important question to ask before you purchase, because water beds are big energy users and some are more efficient than others.

There are currently two types of water beds on the market: the older water-filled vinyl bag in a wooden or plastic frame, and the newer "soft-sided" bed with a smaller vinyl bag surrounded by foam and made to look like a conventional mattress. They range in size from twin to super-king to suit everyone's tastes. Just remember when it comes to heating costs, the smaller the size, the less it will cost to heat.

Water beds are similar to your water heater. Both are containers that hold hot water. Both have a thermostat that controls temperature and both lose heat to the surrounding room.

In the case of a water heater - which holds much higher temperature water - there is generally insulation around the heater which decreases heat loss. Unfortunately, many water beds don't come with insulation. They lose heat out the top, the sides and the bottom.

Recently, some manufacturers have begun to add insulation to the bed frames the mattresses rest in to reduce this heat loss, but not all manufacturers do this. Ask the salesperson about this before you buy.

Newer water beds have better thermostats and heaters than older models. Solid-state heaters allow less variation in the temperature and consequently are on less often. Older-style water beds use between 100 and 135 kilowatt hours per month when heated to 85 degrees in a 65 degree bedroom.

At local rates (5 1/2 cents/kwh) it can cost up to $90 a year to keep the bed warm. Water beds equipped with the newer heaters and the newer soft-sided models, because of smaller amounts of water and better insulation, use about one half that much electricity.

The energy usage of your water bed may vary depending on the amount of insulation on the sides and bottom of the bed, the temperature of the water in the bed, the temperature of the bedroom, the size of the bed and whether or not the bed is made. Keeping the bedroom warmer, particularly during the day, will decrease heat loss from the bed to a cold room.

Perhaps the easiest thing to do to reduce heat loss from your water bed is to make it every day. By making the bed with a heavy quilt or comforter, you can reduce heat loss from the top surface significantly. Regardless of the type of water bed you have, leaving the bed unmade can double the cost of heating it.

Buying as efficient a water bed as possible and following a few simple tips can help you rest easy when it comes to the heating costs of your water bed.

Water bed energy tips:

-- Make your water bed everyday and cover it with a comforter.

-- Buy the most efficient bed you can. Extra insulation and more efficient heaters will cost more to begin with, but will save in heating costs over the life of the bed.

-- Fill your bed with the correct amount of water. Overfilling just gives you more water to heat and keep warm.

-- Keep your bedroom temperature comfortable. A cold bedroom will greatly add to water-bed heating costs.

-- If you're going to be away from home for more than a week, lower your water-bed thermostat to 70 degrees. Home Clinic answers questions about home maintenance, repair and energy conservation. It is prepared by the Energy Extension Service, a division of the Washington State Energy Office. It appears Sundays in the Home/Real Estate section of The Times.