from what I understand the law applies to Hot water and I believe it is 80% of all Hot water produced in a building has to be supplied by solar energy. However the same doesnt apply (as far as I know) to photo voltaic (ie electricity generating) solar panels.
I recently asked the question why when building a villa do constructors not at least give the option of a pV system.
The cost of such a system to run a house is about €40,000 but connected to the grid would produce about €4,500 of income per year, which would pay for itself in 10 years. Not to mention you would get free electrricity (every unit you use you are being paid 36c as opposed to 44c tat you dont use)
The answer it seems is because of te time it takes to get a licence from Iberdrola, but I for one would certainly hae such an installatin even if i had to wait a year for connection. Imagine the sales value of being able to say this house generates an income of €4,500 per year rising yearly – and it is sligtyly more expensibe than next door tat doesnt