Solar energy is a renewable and abundant energy source that is a natural choice for an energy mix with resilient energy production. The concept of luminescent solar concentrators (LSCs) was invented in the 1960-1970s but was at that time too expensive. Today the LSC concept can be motivated by the attraction of coloured and transparent photovoltaic (PV) technologies that can be adopted into building-integrated PV (BIPV). LSC is based on total internal reflection of re-emitted light which is then waveguided to the edges to be converted into electricity by PVs mounted at the edge perimeter. As LSC PV devices rely on total internal reflection, the optical attenuation of the glass is an important parameter for its overall performance. In this study we have investigated three different common flat glass compositions; soda lime silicate (SLS), soda borosilicate (BF), soda aluminosilicate (AS) and discuss how their molar extinction coefficient of Fe2+ ions effects the waveguide efficiency of a LSC PV concept. As-received glasses as well as re-melted glasses spiked with Fe(III) oxide were investigated and the molar extinction coefficients of Fe2+ calculated to 26.9, 22.8, 19.4 L mol-1 cm -1 for SLS, BF and AS respectively which corresponds quite well to found literature data for SLS and BF. This suggests that AS would be the best performing glass for LSC, however, the iron content of the specific glass product ultimately matters most. The structural effects on molar extinction coefficient of the different glass compositions are discussed in relation to both optical basicity and refractive index fluctuations in the glass. Based on the obtained data we estimated the waveguide efficiency using SLS, BF and AS where it follows the order of BF>AS>SLS based on 0.01 wt% Fe-content, however, if using Fe2+ concentration in mol/cm³, the waveguide efficiency would follow the order of the molar extinction coefficient, AS>BF>SLS.