Manufacturers of portable, electric room heaters with quartz elements that radiate heat claim you can cut your heating costs by using this "small heat" while turning down the thermostate on your "big heat."

In theory, this makes sense. Why have your furnace on, gulping oil, burning gas or wasting electricity if you can be satisfied with the heat from a small unit that uses far less energy?

The trouble is, you have to be standing or sitting in one place for these radiant quartz heaters to keep you warm. Because they have their heating elements wrapped in quartz, they can burn much hotter and emit much more radiant warmth than most ordinary electric resistance heaters.

The quartz heaters have reflectors and direct a beam of heat right at you. You get warm fast if you're in front of the beam, but you get cold fast if you're out of it because these heaters do very little to warm the air.

They're ideal for situations where you might be sitting in one spot for long periods of time (watching TV in the evening or sewing during the day). You bask in their warmth while your overall home heat has been turned down to a setting of, say, 60 or even 55.

They are portable so you can carry them to another spot, if necessary. But too much moving around or too many people needing heat in different rooms reduces the quartz heater's usefulness.

This type of heater is also quite useful in large, cold areas such as a garage or basement to heat an individual who is puttering at a workbench. They're also good if you need to work or sit in a cold, enclosed porch area.

Using a regular heater that has to heat the air would not do the job under these circumstances. Many of the older type electric resistance heaters (with little fans inside) heat the air in an entire room, and this is difficult, if not impossible, to do in a large, cold area.

But there are some "combination" heaters that might be your best bet for most circumstances. They heat the air, but they also send out radiant heat, although not as much as the quartz heaters. You get a bit of both -- radiant heat and convection heat (warming the air).

This type of heater would probably be better for someone who is working in a kitchen area and has to move around. And, if you don't mind waiting a bit for your heat, this type of heater might also be good for keeping you warm while watching TV (with the thermostat set back to 60 or 55) or while sewing or doing some other sedentary task.

There's a big difference in price between the two types. You have to pay $70 and up for a quartz heater (although some are occasionally on sale for $50) while a combination radiant-convection electric heater will be priced in the $20 range (sometimes cheaper on sales).

If you can find plenty of times to turn your thermostat down while using your little electric heater to keep warm, you can cut your heating bills. And, of course, the pay-back period for recouping your investment will be a lot shorter with a $20 combination heater than it will with a $70 quartz heater.

If you do buy a heater -- quartz or combination -- pay special attention to the safety features. How easy is it to stick a finger or some object into the heated element? How sturdy is the heater's base? Will it tip over fairly easily? Does it have a cut-off switch if it tips over?

Shop around. Some heaters definitely have more safety features than others.

Q. We are considering installing a one-piece acrylic bathtub-shower unit instead of the regular steel tub-and-tile wall unit. How do these one-piece acrylic units wear over 5 to 10 years?

A. They wear quite well, if you take proper care of them. This means using a nonabrasive cleaner instead of the usual bathtub powder cleaner. You have to use a special liquid cleaner and stick with it.

In general, a one-pice, acrylic shower and bathtub unit is less expensive to install than the traditional enameled steel tub with tile to protect the walls.

In my area, a one-piece unit installed costs around $625. A regular tub with tile walls costs around $725.

But, you can't get a one-piece unit into many homes. Won't fit through the doors. You have to get a multipiece unit, and their quality is not the same (they're not always water tight).