Solar (photovoltaic) cells convert sunlight directly into electricity. if solar cells were 100% efficient, they would generate about 1000 watts of power per square meter of surface area when exposed to direct sunlight. with lower efficiency, they generate proportionally less power. for example, 10% efficient cells generate 100 watts of power in direct sunlight. suppose you want to supply 1 kilowatt nothing of power to a house by putting solar panels on its roof. for solar cells with the average power of 49 watts per square meter of solar panels, how many square meters of solar panels would you need? assume you can make use of the average power from the solar cells (by, for example, storing energy in batteries until it is needed).