Abstarct: In this study, the analysis of energy and exergy of a horizontal axis wind turbine baxsed on blade element momentum theory (BEM) is presented. The computations are validated against wind tunnel data measured in the MEXICO wind turbine experiment. Results show that the blade element momentum theory has good ability to predict the energy and exergy efficiencies. The computations of energy and exergy show the wind speed has hight impact on the energy and exergy efficiency. With increasing the wind speed from 8 m/s to 14 m/s the energy and exergy is increased. In the wind speed 14 m/s energy and exergy is maximum. In this speed the exergy efficiency is 39.86% and energy efficiency is 44.05%. The computations of energy and exergy exhibit that with the increasing the roughness from 0 mm to 0.5 mm, 2324 W of the output power is reduced. Roughness of 0.5 mm at the wind speed of 14 m/s reduced exergy efficiency 14.73% respectively. It’s also found that the roughness in the first four months of the operation has a more negative effect on the wind turbine performance. The other metrological variables like pressure, temperature and moisture don’t have remarkable impact on wind turbine performance. In wind speed 15 m/s with increasing the temperature from 281K to 286K the exergy efficiency 3.31% is increasing. Also with increasing the pressure from 100KPa to 105KPa the exergy efficiency 3.31% is decreasing. With increasing the relative humidity from 65% to 75% the exergy efficiency 0.4% is decreasing. The computations of energy and exergy exhibit that with the increasing the yaw angle from 0 degree to 15 degree in wind speed from 10 m/s to 24 m/s the energy and exergy efficiencies have a bit decreasing than energy and exergy efficiency at yaw angle 0 degree. at the wind speed from 18 m/s to 24 m/s, at yaw angle 30 degree, with increase in the wind speed, energy and exergy efficiency of wind turbine is increases. In wind speed 24 m/s at the yaw angle 30 degree, the energy and exergy efficiencies are reached up to 28% and 26%, respectively. They are increased 5.24% and 3.37%, comparing to the energy and exergy efficiencies at the yaw angle 0 degree in the same speed. And also it is recommended that don’t use the yaw angle 5, 10 and 30 degrees at the wind speed from 10 m/s to 16 m/s.