To choose the most suitable solar cell for desert climate, measurements and analysis of the integrated spectral response (ISR) and the electrical power over 32 spectral bands for monocrystalline, polycrystalline and amorphous solar cells have been carried out in Helwan during several seasons under different environmental conditions. The results of ISR show that while the amorphous silicon solar cell is sensitive in the visible part of the spectrum with maximum sensitivity at wavelength (lambda=0.522 mu m), the polycrystalline silicon solar cell shows remarkable sensitivity in the infra-red region with maximum sensitivity at (lambda=0.922 mu m) and the monocrystalline silicon solar cell is more sensitive in the near infrared spectrum with maximum value of sensitivity at (lambda=0.704 mu m). Deviations were found in the behavior between the ISR and the electrical output power in the measured bands.