In order to produce a sufficient quantity of propellant on the surface of Mars for the return of a Starship (SpaceX) to Earth, there are various means of energy production. Musk wishes to use photovoltaic panels as a primary source of energy to meet this need. According to the work of Cooper et al, solar panels in conjunction with batteries or fuel cells are indeed very effective, perhaps even more than nuclear energy on the kW per kg basis. However, there are several drawbacks: The solar energy received on Mars is half that received on Earth due to the greater distance from the sun. A huge surface of solar arrays would thus be required, which is highly impractical for the deployment, even using very thin layers. Moreover, solar panels produce energy only during the day and the deposit of dust could dramatically affect their efficiency. According to our calculations the total mass of ISRU systems plus power systems would be between 180 and 247 tons, depending on the rate of water molecules present in the Martian soil. As a consequence, the feasibility of the proposed strategy is doubtful and new options might have to be investigated.