SEER is most commonly used to measure the efficiency of a central air conditioner. SEER measures how efficiently a cooling system will operate over an entire season. The higher the SEER, the more efficient the system.
Energy Efficiency Ratio (EER)
EER is a measure of how efficiently a cooling system will operate when the outdoor temperature is at a specific level (95°F). The higher the EER, the more efficient the system.
Heat Seasonal Performance Factor (HSPF)
HSPF is the most commonly used measure of a heat pumps heating efficiency. The higher the HSPF, the more efficient the heat pump.