The term E.E.R stands for Energy Efficiency Ratio and is a measure of the energy efficiency of an air conditioner or heat pump. It is calculated by dividing the cooling capacity of the unit (in British Thermal Units, or BTUs) by the power input (in watts). The higher the E.E.R, the more efficient the unit is. The minimum E.E.R for residential air conditioners and heat pumps is currently set at 8.0, meaning that the unit must have an E.E.R of 8.0 or higher to be considered energy efficient. An E.E.R of 10.0 or higher is considered to be very energy efficient. It is important to note that the E.E.R is only one factor to consider when selecting an air conditioner or heat pump. Other factors such as size, noise level, and features should also be taken into account. Additionally, it is important to remember that the E.E.R is only an estimate of energy efficiency and may not accurately reflect the actual energy usage of the unit.