AFUE stands for Annual Fuel Utilization Efficiency. AFUE is a rating that reflects how efficiently a gas furnace converts fuel to energy. For example, an AFUE of 90 means that approximately 90% of the fuel is used to provide warmth for your home, while the remaining 10% escapes as exhaust.

SEER stands for Seasonal Energy Efficiency Ratio. SEER is a rating that measures the cooling efficiency of an air conditioning unit. The higher the SEER rating is the more efficient the unit will be.