# EFFICIENCY RATIO

The Energy Efficiency Ratio (EER) is the ratio of output cooling in Btu/h to energy input in watts. It is at a given single outside temperature.

EER = cooling in (BTU /h)/ energy input in watts

Calculate EER  at 950F outside temperature. The return air temperature is 800F and 50% relative humidity.

#### Calculate COP under a set of inside and outside design conditions. There are summer and winter outside design conditions. Cop is ratio of cooling effect to energy input in summer. In winter, COP is the ratio of heating effect/energy input. COP refers to year round air conditioning.

COP = N/W

N is the cooling effect say in watts

W = work input in watts

#### EER = COP * 3.412

The EER is related to the coefficient of performance. The primary difference is that the COP of a cooling device has no units i.e. uses same units of the cooling load and the electrical power input. Therefore  COP is same in any system of units. Values of EER will be different in different units.

EER = COP * 3.412

#### SEER is a higher value than EER for the same equipment.

RELATION BETWEEN EER AND SEER

EER for residential central cooling units = 0.875 × SEER

SEER has a higher value than EER for the same equipment.

In a nut shell

EER=0.875 x SEER

EER = COP x 3.412