Solar panels. Array of solar panels (photovoltaic cells) on the roof of terraced houses in Heerhugowaard in The Netherlands. This is part of a Dutch government pilot project to investigate clean, renewable energy forms such as solar power. The ten houses in this terrace (only two seen here) have a total of 200 square metres of solar panels on their roofs. The total power output of these solar panels is 24. 6 kilowatts. The photo- voltaic cells contain a semiconducting material which converts sunlight directly into electricity. Solar power is relatively cheap, as once the panels are installed they continue to produce electricity indefinitely.