Private investment in solar panels used to generate electricity has increased sharply in recent years, economic affairs minister Henk Kamp said in a letter to parliament on Tuesday.

Since 2011, the growth in investment has averaged 91%, compared with just 13% from 2004 to 2010, Kamp said.

The minister attributed the increase to the development of a method whereby unused electricity generated by private individuals is pumped directly back into the grid. The homeowner’s electricity bill is then reduced accordingly.

The availability of governement subsidies and the sharp reduction in the cost of solar panels had also played a part, the minister said.

Kamp based his report on research carried out by consultancy PwC working with many Dutch interest groups. He said the report comprised the building blocks for stimulating renewable energy after 2020.