Interest in solar panels has declined sharply in the past year, installation companies have previously noted. This is also reflected in the delivery times. A year ago, solar panels were only on the roof six to nine months after purchase. Now companies can often deliver within a month. “People have doubts about purchasing because of the phasing out of netting and the feed-in tax from energy companies,” says Mariken Stolk, sustainable energy expert at Milieu Centraal.