## 2 Materials and Methods  
### Data Collection  
As mentioned in Section 1, the hourly values of the meteorological and radiometric data included in the 33 TMYs-PV were used. Each TMY file contained 12 typical meteorological months (TMMs), which were selected through an appropriate statistical procedure from a database covering the time period of 1985-2014 (30 years). The meteorological data (ambient temperature in degrees Celsius and relative humidity as a percentage) were measurements from an equivalent number of meteorological stations operated by the Hellenic National Meteorological Service (HNMS), showed in Figure 1. The radiometric data (global and direct horizontal irradiances in Wm\({}^{-2}\)) were simulations performed by the Meteorological Radiation Model (MRM) [56; 57], since the HNMS network does not include solar radiation measurements. More details about the generation of the 33 TMYs across Greece can be found in [54]. It should be mentioned here that each TMY-PV consisted of TMMs belonging to different years in the 30 year period. Each TMM was selected through an appropriate statistical procedure [54], being the most representative month climatologically in the examined period. Table 1 shows the years from which the 12 TMMs at 4 HNMS stations were selected.  
The definitions of the four climatic zones of Greece are given in Table 2, according to the technical guidelines (TOTEE) established by the Technical Chamber of Greece [58], where HDD stands for heating degrees days, CDH stands for cooling degree hours, and SSR stands for surface solar radiation.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline
**Station** & **Jan** & **Feb** & **Mar** & **Apr** & **May** & **Jun** & **Jul** & **Aug** & **Sep** & **Oct** & **Nov** & **Dec** \\ \hline Agrinio & 1999 & 2004 & 2000 & 1994 & 2001 & 1997 & 2000 & 1999 & 2004 & 1988 & 2010 & 1994 \\ \hline Irakleio & 1995 & 2001 & 2004 & 1994 & 1997 & 1987 & 2003 & 1996 & 1996 & 1997 & 2004 & 2003 \\ \hline Kastoria & 1987 & 1988 & 2005 & 1985 & 1995 & 1996 & 1996 & 1998 & 1991 & 1994 & 1989 & 2008 \\ \hline Tripoli & 1999 & 1985 & 1993 & 1993 & 1995 & 1987 & 1987 & 1986 & 1986 & 1991 & 2004 & 1994 \\ \hline \hline \end{tabular}
\end{table}
Table 1: The Helenic National Meteorological Service (HNMS) stations of Agrinio, Irakleio, Kastoria, and Tripoli with their typical meteorological months (TMMs) selected from different years in the time period of 1985-2014.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Climatic Zone** & **HDD (Dimensionless)** & **CDH (Dimensionless)** & **SSR (kWhm\({}^{-2}\).year\({}^{-1}\))** \\ \hline A & \(<\)1000 & [1300, 4500] & [1700, 1900] \\ \hline B & [1000, 1500] & [2200, 5500] & [1500, 1700] \\ \hline C & (1500, 2000] & [1200, 3800] & [1450, 1600] \\ \hline D & \(\geq\)2000 & \(\leq\)1500 & \(\leq\)1500 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Range of annual heating degrees days (HDD), cooling degree hours (CDH), and surface solar radiation (SSR) values to define the climatic zones in Greece for energy-saving in buildings [58]. The calculation of HDD and CDH considers the following cold and warm periods of the year: (1) climatic zones A and B, November 1–April 15 and May 15–September 15, respectively, and (2) climatic zones C and D, October 15–April 30 and June 1–August 31, respectively.