Installing solar panels on roadways to generate electricity, fight climate change and create new revenue streams for countries was a bold idea a few years ago. France installed them on the Tourouvre-au-Perche highway and the early results from years of data logs are abysmal. Energy generated is only 50% of what it was supposed to generate and the road capacity factor, "which measures the efficiency of the technology by dividing its average power output by its potential maximum power output is just 4%." When compared to a solar plant that has the ability to track the sun as it moves across the sky, the roadway costs 10 times as much to build and generates only 1/3 of the power. Also it is pointed out in the article that there are only 2 billion square meters of roadway in the UK, but 17 billion square meters of rooftop in urban areas alone. Unable to benefit from air circulation, its inevitable these panels will heat up more than a rooftop solar panel too. For every 1C over optimum temperature you lose 0.5% of energy efficiency. As a result a significant drop in performance for a solar road, compared to rooftop solar panels, has to be expected.