A simple method of estimating the height variation of the mean wind power density is presented which accounts for the variation of the exponent p of the wind speed power law, with stability and roughness. Measurements are used to compare the new method to two previously suggested methods. The results indicate that the presently suggested method gives the most accurate estimate of the extrapolated mean wind power densities. Abstract A simple method of estimating the height variation of the mean wind power density is presented which accounts for the variation of the exponent p of the wind speed power law, with stability and roughness. Measurements are used to compare the new method to two previously suggested methods. The results indicate that the presently suggested method gives the most accurate estimate of the extrapolated mean wind power densities.