Solar energy reaching the earth is about 1350 W/m² outside the earth’s atmosphere, and 950 W/m² on earth’s surface normal to the sun on a clear day. Someone is marketing 2 m × 3 m photovoltaic cell panels with the claim that a single panel can meet the electricity needs of a house. How do you evaluate this claim? Photovoltaic cells have a conversion efficiency of about 15 percent.