We have PV panels but haven't had them long enough to answer your question re savings yet. Seems it depends how many panels and how big they are - not to mention how bright a day it is. PV panels need brightness rather than sunshine. We're with EDF so we get so much for everything we generate and then a bit less for their estimate of what we use (about half of what we generate). Bill should go down as well if we use power as we're generating it so we try and do as much as we can during the day now. When we were analysing the cost and whether it was worth it (other than the "green" aspect we reckoned it would take about 12 years to get our money back.