A leading consumer magazine recently surveyed over 500 contractors and reported the following tips on purchasing a central air-cooling system:

Choose the right-sized air conditioning system. If it is too small, then it won’t cool properly; if it is too large, then it won’t dehumidify properly.

Invest in an 11-14 SEER model. 11-14 SEER are recommended for their combined performance in increased energy efficiency and product reliability.

Beware of replacing only one of the two main components if shopping for a replacement system. Replacing only the indoor or the outdoor unit of a system may result in a mismatch that compromises efficiency. Contractors also said these systems are more prone to repairs than systems where the two units have been bought and installed together.

Think twice about buying a zoned system. Contractors said that zoned systems (which alter airflow to different zones in the house) require more cooling-equipment repairs than regular systems.

Look for an experienced contractor. One-fifth of the contractors surveyed said the primary reason for their service calls was improper application or incorrect installation.

Maintain your system properly. At least 40% of surveyed contractors said that service calls were primarily the result of improper maintenance.