TUCSON, Ariz. — Maintaining an air conditioning unit properly is one of the easiest ways to reduce energy costs, said Wade Hamstra, the general business manager for Hamstra Heating & Cooling, Inc.

"An air conditioner works like any other piece of machinery. If you never change the oil in your car, and you never have it serviced, it won't run well and you won't get good gas mileage," Hamstra said. "It's the same thing for your unit. If you don't maintain it, it will get worse and worse and worse."

Hamstra Heating & Cooling, Inc., as well as similar companies offer maintenance services.

With Hamstra, customers pay $100-150 a year to have a professional "check all the vital things to make sure they are working correctly." The service includes a visit in the spring with another in the fall.

Quick Tips Wade Hamstra of Hamstra Heating & Cooling, Inc., offers his top three ways to make your heating and cooling unit more energy efficient. Upgrade — "If you've got an older AC system, it has a lower SEER (seasonal energy efficiency ratio) but higher is better. They go up to about 21 SEER," he said. "If your unit is 10 years old, it's probably 8-10 SEER. The minimum anyone can sell now is 13." Resize — Air conditioners are "not like an evaporate cooler where bigger is better," he said. But most people have units that are not properly sized for their home. Maintain —"If you don't take care of it now, it will cost you in the long run," Hamstra said. Replace filters when they become clogged.

"We do it then so when summer hits, you know that the unit will hold up well when it gets hot," Hamstra said. "In the fall, we check up on the heating side of it."

But in addition to having a professional service the unit twice a year — "once is better than not but twice is optimal" — Hamstra also recommends that homeowners do a monthly check up.

"A huge thing is to check the filter monthly. You don't necessarily have to replace it monthly but you should at least check it," Hamstra said. "The No. 1 cause of a unit not running efficiently is people not changing their filter."

When the filter becomes clogged with substances such as dirt and dust, it can cause the components inside of the unit to stop working properly. And that can result in higher energy bills as well as additional costs for unit repairs.

"Pull it out and if the filter is concaved — if it's not completely straight —that means that it's really clogged up," Hamstra said. "If the filter is visibly dirty and you can't see through it at all, you definitely need to change it."

For more information on improving the energy efficiency of your heating and cooling system, "read the heating and cooling advisor section on our Web site," Hamstra said. "There are a million questions that we came up with an answer for so it's a good resource for everyone."