This paper addresses the problem of peak power evaluation in HF OTH skywave radar. A wide number of factors affect the performance of such systems, specifically ionospheric propagation and absorption losses, as well as external radio noise interferences. A normalized version of the signal to noise ratio (SNRN) has been introduced in order to evaluate the power requirements over a wide range of environmental conditions. Finally, this paper attempts to provide a method for evaluating the peak power values required in OTH radar systems and also some useful project criteria.