Do I have to be concerned with my unit's Energy Efficiency Rating (EER)?

The EER of your air conditioner can be compared to your car's gas performance. That is - your car's kilometres per gallon indicate how many kilometres you can drive on a gallon of gas. In the same way, a higher EER indicates that more BTUs of heat can be removed on a single watt of power. You save money by using less electricity to run your machine.

What size air conditioner should I buy?

The size depends on the area you want to cool down. To estimate, calculate the square footage of your area (e.g. - a 10' by 8' room has 80 square feet), and multiply it by 20 (80 sq. ft. x 20 = 1600 BTU). You would need to purchase a 1600 BTU air conditioner.

Last year my air conditioner seemed to work better. What could be the problem?

Make sure the filter is clean. Dirty filters cut the unit's power and efficiency. Give the evaporator coils a good vacuuming. They need to be clean to do their job well. If the unit is still not functioning up to par, have it checked by a professional service technician.