The SEER (Seasonal Energy Efficiency Ratio) and the EER (Energy Efficiency Ratio) are very closely related. Have you ever taken the time to assess this type of letter? Are you aware of the changes in energy usage throughout your home when youre running your furnace or your air conditioner?To get the SEER, the efficiency of your unitis calculated using different sets of conditions. Energy efficiency ratio is calculated by dividing the power consumption, or input, of a machine by the cooling power of the machine (in BTUs) under a certain set of conditions. To determine the SEER, the performance of the device under different outside temperatures, ranging from 65 to 104 degrees Fahrenheit is considered. The average of these energy efficiency ratios is usually the figure that is put on AC machines. The government requires manufacturers to indicate the SEER ratings on the units they manufacture. While manufacturers are not required to put the EER ratings, many units still have this rating.