Solar power is being used to satisfy a higher and higher percentage of our energy needs. We must be able to evaluate the performance of the hardware. Here we present an analysis of the performance of a fixed grid of 13 solar panels installed in the spring of 2021. We confirm that the power output is linearly proportional to the cosine of the angle of the incidence of sunlight with respect to the vector perpendicular to the panels. However, in order to confirm this, we need to consider the dimming effect of the Earth's atmosphere on the intensity of the Sun's light, which is to say we need to rely on astronomical photometric methods. We find a weighted mean value of 0.168 +/- 0.007 mag/airmass for the extinction term, which corresponds to the sea level value at a wavelength of about 0.76 microns. As the efficiency of the solar panels is expected to degrade slowly over time, the data presented here provide a baseline for comparison to the future performance of the system.