If your current air conditioner is more than eight years old, it's time for a new one. Over the life of the product, the amount you'll save in energy bills will more than likely exceed the cost of the new unit.
The following are basic criteria to use when choosing a new system:
BTUs: The cooling capacity of an air conditioner is measured in British thermal units per hour (Btu/hr). To find the best BTUs needed to cool your room, multiply the square footage of the space by 10 and then add 4,000.
Energy Star rating: The Environmental Protection Agency's Energy Star ratings indicate that an appliance is at least 10 percent more energy-efficient than the minimum federal standards.
EER: A room air conditioners EER, or Energy-Efficiency Ratio, is the ratio of the cooling output divided by the unit's power consumption. The higher the EER, the more efficient the model.
Anti-Microbial filter? Most room air conditioners come with reusable electrostatic filters, which may be treated with triclosan. If purchasing a unit with an antimicrobial filter, ask the retailer to replace it with an untreated electrostatic filter.
If you live in a very humid climate, look for models that are good at removing moisture; ask about the rate of water removal (in pints per hour).
At the store, compare the energy consumption and usage costs of one model to another using the yellow "Energy Guide" label on the product.