This work is part of the "PROPRE.MA" project which main goal consists on drawing gridconnected photovoltaic yield maps for all Morocco with ground calibration using identical plants installed in partner institutions located in 20 different Moroccan cities. To have monthly calibration corrections as small as possible, the monthly maps before calibration must be as realistic as possible, and above all, the calibration factors undergo the least possible temporal and spatial variations. From an investor perspective, the specific energy yield is the most important parameter since it has and immediate effect on the levelized cost of electricity (LCOE), with all its impacts. In this paper, we estimate expected monthly averages of daily energy yields with methods which use solar maps published by weather services dedicated to solar energy. We present a comparison of monthly averages of PV daily yields calculated with our own models as well as with values obtained from international databases. In terms of methodology, our paper refers always to the results of an hour-by-hour simulation software. Whatever picture we take, we find that linear “simple models” tend always to overestimate yields and we explain why. We propose a non-linear model which seems to be the best compromise for our future PV yields database.