According to the Tax on Constructions, Installations, and Works (ICIO), it is necessary to pay a fee of 4% or 5% of the total budget when installing solar panels. That is, if the cost of installing 8 solar panels is €5,800, the ICIO fee at 4% would be approximately €232. To this amount, you must add the municipal fee, which can range from €6 to €300 depending on the municipality.