Seasonal Energy Efficiency Ratio (SEER), is most commonly used to measure the efficiency of a central air conditioner. The higher the SEER, the more efficient the system. SEER measures how efficiently a cooling system will operate over an entire season.
Energy Efficiency Ratio (EER) is a measure of how efficiently a cooling system will operate when the outdoor temperature is at a specific level (95oF). The higher the EER, the more efficient the system.
Both SEER and EER are included in the ENERGY STAR specification because each rating indicates the energy efficiency of the product under different operating modes. SEER rating more accurately reflects overall system efficiency on a seasonal basis and EER reflects the system’s energy efficiency at peak day operations. Both ratings are important when choosing a product.
Heat Seasonal Performance Factor (HSPF) is the most commonly used measure of a heat pumps heating efficiency. The higher the HSPF, the more efficient the heat pump.