Air conditioning units today are more efficient using less energy and cooling your home faster than older units. That reduction in energy can eventually result in significantly reduced energy bill costs. Depending on your unit, even if your unit is still functioning, purchasing a new unit could significantly reduce your energy bills over time. A well-maintained unit could be efficiently running after 12 or more years, however, an overused, non-maintained unit may have a drastically reduced lifespan. When purchasing a new unit, consider SEER. Each energy efficient air conditioner model comes with a Seasonal Energy Efficiency Rating (SEER), spanning a points system of 13-21 SEER. The higher the SEER, the more efficient the unit, the lower the amount of energy consumed when running the air conditioner, and the lower your energy bill.