The heat is on. And if your air-conditioner is off, or just not running efficiently, you or your wallet are suffering.

Dale Dorman, a housing specialist with the University of Georgia Extension Service, says good maintenance in hot weather can save you both discomfort and money.

"Cooling experts recommend having your system inspected and served by a qualified contractor," Dorman says. "The best person to call is the one who installed it or the manufacturer's local representative listed in the Yellow Pages."

Dorman suggests these tips to keep your system running its best:

* Shade your room air-conditioner from direct sun. This will reduce its workload.

* Clean the filters every month and replace them as necessary. This will save energy and reduce dust and pollen in the air.

* Don't leave your room air-conditioner turned to the coolest setting when you go out. Set the controls to a warmer setting to reduce operating costs.

* Because dust can foil efficiency, vacuum air vents regularly. And don't block them with furniture, carpet or curtains.

* Leaky ducts are prime sources of energy waste. Hire a professional to seal and insulate ducts.

* If your home has crawl space under it, open the foundation vents in the spring to promote air flow. Close them in the winter.

* Prune shrubs that may block air flow to your air- conditioner.

* Think about installing ceiling fans. The air circulation spreads cooling in the summer and boosts heating efficiency in the winter.

When you buy a new air-conditioning system, "you can save a little or a lot," Dorman says. "Select the most energy-efficient equipment that meets your needs and fits your budget."

The more efficient a product, the less it costs to run. It reduces air pollution, too, and helps conserve natural resources.

So what makes one system more efficient than another?

"Most of the differences are on the inside in the motors, compressors, pumps, valves, gaskets and seals," Dorman says. "Or in electronic sensors that make today's products more 'intelligent.'"

Manufacturers use standard U.S. Department of Energy tests to prove their products' efficiency. The EnergyGuide materials from the Federal Trade Commission's Bureau of Consumer Protection report the test results.

Before you buy, use an energy audit to help pinpoint your needs, Dorman says. Audits help detect energy waste and gauge your current system's efficiency. Do-it-yourself kits are available.

Find out about special offers. Ask your local utility or salesperson about cash rebates, low interest loans or other incentives for buying energy-efficient products. You may qualify.

If you're buying a home, ask your lender if an Energy- Efficient Mortgage is available. EEMs allow home buyers to qualify for a larger mortgage. Lenders use the lower monthly bills you'd pay in an energy-efficient house to offset a higher mortgage payment.