> The limiting factor in solar panel production is cost, not places to put them.

Where did you get that from? From the site of this initiative (http://www.solaroad.nl/en/faq/):

> The total electricity consumption in the Netherlands lays around 110,000 GWh and increases annually by about 3% (according to CBS Netherlands). This means that if all suitable roofs in the Netherlands would be equipped with solar panels, they could only supply approximately 25% of the Dutch electricity demand.