Air conditioners are a great investment for your home. Resale value of a home with AC is significantly higher than a house without an air conditioner. The efficiency rating of an AC severely impacts the cost of using the unit. Seasonal energy efficiency ratio (SEER) is how air conditioners get rated depending on average cost and usage values. Choosing the right unit for your home depends on a few factors; such as, efficiency needs, costs of yearly operation, and reliability of the air conditioner. The higher the SEER rating, the lower the air conditioner costs to operate. The SEER rating of a unit is the cooling output in Btu (British thermal unit) range from a low of 13 to the highest possible rating of 20.