Q. Do the healthy, “mood-lifting” full-spectrum fluorescent tubes use more electricity than common fluorescent tubes? Are there smaller efficient fluorescent lights suitable for lamps and fixtures in homes? — G.J.

A. Full-spectrum fluorescent tubes are just slightly less efficient than standard fluorescent tubes. Some physicians claim that the full-spectrum of light given off by these specially coated fluorescent tubes improve one’s mood. You should consult your own physician. These also provide excellent color rendition and natural-looking light for home use.

The newest and most efficient small residential-sized light bulb is a compact fluorescent bulb. It is designed to screw into a regular lamp socket to replace a standard incandescent bulb. It is just slightly larger than a standard bulb, so it fits most lamps.

These are available with one or two tiny U-shaped fluorescent tubes per bulb. A high-efficiency electronic ballast, inside the bulb, eliminates any hum or flickering. These bulbs are covered with an unbreakable clear plastic diffuser so it looks somewhat like a standard bulb.

Although a compact fluorescent bulb is more expensive than a standard incandescent bulb, it lasts more than 10,000 hours, about 10 to 15 times longer. If you use the lamp for six hours each day, the bulb should last more than five years.

Compact fluorescents use only about 20 percent as much electricity as a standard incandescent bulb for the same amount of light. Over its lifetime, each bulb can lower your electric bills by about $45 to $50.

Since the extra electricity used by a standard bulb ends up as heat in your home, your air conditioner may run less with compact fluorescents. Their light quality is designed to approximate a standard incandescent bulb.

You should determine how often you use a light or lamp before purchasing a more-expensive compact fluorescent bulb. For example, it would take very many years for the electricity savings to payback the cost of one in a closet light fixture used only five minutes each day.

There are some less expensive, yet efficient, lighting options. The older screw-in circular fluorescent bulbs are effective, but difficult to fit in some lamps. Some new incandescent bulbs — krypton-filled, infrared-reflective coated, and tungsten-halogen — are somewhat more efficient than standard bulbs and have a longer life (from 1,000 to 3,000 hours).

You can write to me for UTILITY BILLS UPDATE No. 033 showing information on and manufacturers of full-spectrum and compact fluorescent bulbs, and a buyer’s guide for eight types of new high-efficiency residential incandescent and fluorescent bulbs. Please include $1 and a self-addressed business-sized envelope.

Q. I have been getting quotations on having a new high-efficiency furnace installed. Several of the contractors suggested a furnace that is much smaller than my current one. How can I tell if they are right? — C.W.

A. In order to determine an accurate heating load requirement of your house, the contractor should do a detailed computerized analysis. This includes numerous variables about your specific house.

Don’t be alarmed if he recommends a smaller furnace. Furnaces are rated in input energy usage, not heat output. A new high-efficiency furnace with smaller input can produce as much heat output as your old larger one.

Readers may send questions to James Dulley, c/o Bangor Daily News, 6906 Royalgreen Drive, Cincinnati, Ohio 45244. Dulley studied energy management at the doctoral level at Harvard.