This study presents an alternative methodology for analyzing the difference in daily solar energy generation between two grid-connected photovoltaic arrays (PVAs) that are identical in capacity, technical characteristics, and have the same energy production measurement interval but are in two different municipalities of Mexico City (CDMX). Unlike conventional approaches, which often rely on environmental variables, this work proposes combining the cubic smoothing Spline technique with the separation of trend, seasonality, and cyclicality (TSCI) effects. The first technique reduces random variations in measurement, while the second separates the effects commonly found in time series data. The results obtained are useful for installers of this technology, as they allow them to determine in which borough a greater photovoltaic capacity is needed.