A theoretical model was used to predict the electrical power output by Gallium Arsenide/ Germanium solar cells at the surface of Mars. This model was validated using measurements from the Mars Pathfinder Lander. It was then used to estimate the solar power output as a function of latitude, local time, and season for airborne dust optical depths between 0.1 and 5. For this range of dust opacities, the power output varies by about a factor of three at low and mid-latitudes. This model was also used to estimate the solar cell performance degradation due to dust accumulation. Dust accumulation reduced the power output by 0.4 to 0.5% Martian day during the first 20 days of the mission, but the power loss rate fell to ̃0.1%/day after that. If these power loss rates are typical, solar power provides a viable option for long-lived stations on the Martian surface.