@Edent our housing company estimates were around 6-8 years for a 390kWp solar. That's a lot I know but we have just over 300 apartments and all of our heating comes from a total of 1000 MW (not exact we have 3 pumps) geothermal heat pumps. Our goal was to have 4-6 months of free heating and with the company this large probably nothing will get exported anyway.