Energy giants Vattenfall and Essent are poised to follow Eneco and introduce some form of fee structure for solar panel users who feed electricity back into the national grid.

Both firms have told the AD they are looking at a way of “sharing the costs fairly” and that all options are still open. All three companies have around two million clients.

Eneco said earlier this week that its solar panel customers will have to pay 11.5 cents per kWh to feed back excess electricity but will be able to use that electricity cost free in other periods. By charging solar panel owners, the bills for all clients can come down, Eneco said.

“Nearly all energy providers now impose fees on households that feed solar energy back into the electricity grid,” said Koen Kuijper, from comparison website Energievergelijk.

“Only a tiny minority do not yet do so,” he said. “The fees charged can also vary considerably between providers, so people should compare prices and tariffs carefully to ensure they are getting the best possible deal.”

The Dutch consumer and markets authority ACM said earlier this year that energy firms have to pay several hundred euros per client per year to process their excess electricity and offset it against regular usage.

With more people having solar panels, it is becoming a serious cost item, the ACM said. In addition, the way consumers can offset excess electricity produced in the summer against the darker months is also a financial and environmental issue, given that electricity is more likely to be generated by fossil fuels in the winter.

The ACM is planning to publish a detailed report on the impact of solar panel fees later this month.

Almost one in three Dutch households now have solar panels on their roofs, according to grid management company Netbeheer Nederland. In total, Dutch homes now have 2.6 million panels, a rise of 600,000 from a year ago.