Q. I read an article that recommended ceiling fans to help cut energy costs. I looked at the selection of fans at a home-improvement center and now I am thoroughly confused. They range from about $40 to nearly $500. The clerk tried to sell me one of the more expensive models. If I spend too much money on a fan, I doubt that I will be saving that much on my energy bills. Do you have any information on what to look for in ceiling fans and how practical they are?

A. A ceiling fan can supplement or replace air conditioning and make a big difference in both the comfort of your home and your energy bill. With sufficient air movement you can feel comfortable at higher temperatures. For example, a fan that runs as a complement to your air conditioner can make a room with a thermostat setting of 78 degrees feel as if it's 72 degrees. That means you can turn up the thermostat and save significantly on your cooling costs--according to some studies, by up to 30 percent.

Even an expensive fan can pay back its cost in utility savings. Yet while ceiling fans may basically look alike, there are significant quality and structural differences among them.

It's not wise to buy the lower-priced models. Within a year the fan may wobble excessively and the motor may hum. However, this doesn't mean that for durability and efficiency you have to invest in the most expensive models. Sometimes the differences have more to do with cosmetics than efficiency.

Things to look for in fan construction are motor housing material, bearing type, motor size, blade pitch, range of speeds, automatic speed and lighting controls, and sound/vibration isolating features.

Die-cast or cast-iron housings are best. These are made to close tolerances. This heavier metal, as compared with a thin steel stamping, dissipates heat better, is more durable and provides longer motor life. A larger, more powerful motor also runs cooler and quieter.

Double-shielded, permanently lubricated bearings are most durable and quiet. When fan bearings are shielded on one side only, they're exposed to dust and can wear prematurely. Look for other motor or fan housing elements that reduce wear. Corrosion-free parts and a housing that promotes thermal conduction mean the fan will run cooler. Direct-drive motors have fewer moving parts, less friction and less wear. Also, be sure to look for sound- and vibration-reducing components between all metal parts.

A steeper pitch angle of the blades is better and moves more air at a lower speed. Most better-quality fans have a blade pitch of 13 degrees to 14 degrees. Moisture warps inexpensive or improperly sealed fan blades. The best fan blades are made of laminated or solid hardwoods, which resist moisture and warping.

Fans can wobble when cheaply made rotors get out of balance, or when blades are unmatched in pitch and weight.

Fans are available in many finishes. A quality finish is tarnish- and scratch-free and results from multiple plating or enameling processes. A final clear coating gives extra protection.

Before you buy, consult the manufacturer's brochure or catalogue for add-on light kits, replacement blades, wall-mounted or remote-control units and other accessories you may want to add. Be sure the manufacturer has a network of repair or replacement-parts facilities. Manufacturers' limited warranties run from five years to the lifetime of the fan.

I have a large ceiling fan that is poorly balanced, so that it can be operated only at the slowest speed. Otherwise, it wobbles badly. Can you explain how to balance such a fan?

There are a number of factors that can cause a ceiling fan to wobble excessively. To troubleshoot the problem, start by inspecting the installation of your fan. Because there is no one way to install a ceiling fan, consult the installation instructions that came with your model. Read them carefully and double-check every step.

Your fan may not be secure on the hanger assembly, or the mounting screws may require tightening. The blade brackets may not be attached to the proper locations. The fan could be installed too close to a vaulted ceiling.

If your ceiling fan has a light fixture, check with a fan outlet store or the manufacturer to make sure your light fixture is appropriate for your fan. If an improper light fixture has been installed, it will disrupt the balance of the unit.

If your fan still wobbles after this type of checkup, you will have to look further for the vibration problem. Accumulated dust and dirt can disrupt the fine balance of a ceiling fan. Clean the blades and, during the process, check for loose blades or blade brackets and tighten all screws.

If any of the blades are cracked or warped--they should lie flat when placed on a flat surface--replace the entire set, not just a single blade. Blades are manufactured in sets to maintain accurate blade balance (be sure to purchase the blade set made for your brand and model of fan).

Examine the blade irons. The irons are made to sit at a 12-degree angle. If one of them becomes bent, it disrupts the balance. Stack the blade irons on top of one another to ensure that they all match. If one is out of alignment, have it replaced.

With the blades and irons removed, check the motor by turning the fan on to its fastest setting. It should not wobble. If it does, have the motor checked for repairs by an authorized repair center for your brand of fan. If the motor doesn't wobble, and the fan still vibrates when you reassemble the unit, you can use small weights to fine-tune the balance of the blades.

Balancing kits are often included when you purchase a fan. They are also available at home centers or from your local fan dealer. These kits include weights that can be attached to the tops of the fan blades. The balancing process can be tedious, but it is not difficult if you follow the manufacturer's directions. Sometimes it's best to keep the weights in place with masking tape until you have achieved the correct balance. Then the weights can be glued on the blades as permanent attachments. The weights that come with the kits have self-adhesive backings.

I recently read your article regarding removal of hard-water stains from a toilet bowl. It reminded me of the hard-water stains that collected in our toilet while we were living in military housing. The housing inspector for the project recommended a pumice stone, such as those used to clean swimming pools. It worked wonderfully, and is much safer than an acid cleaning solution.

Thanks for the reminder. A pumice stone is excellent for cleaning stained porcelain sinks, bathtubs and toilet bowls. It simply takes a little elbow grease, and the stained surface of a fixture can look like new. But it won't restore a cracked or pitted surface.

Write to Here's How, Copley News Service, P.O. Box 120190, San Diego, Calif. 92112-0190, or e-mail copleysd@copleynews.com. Only questions of general interest can be answered.