In the GB (UK mainland) grid only ~2% of energy is lost in transmission; distribution is more typically ~5%. And we did put most of our big thermal power generation in the middle of the country, which is now causing difficulties as we need to re-jig transmission to accept offshore wind and interconnectors.

Solar PV on rooftops is great, injecting power directly at the load, eliminating transmission and distribution losses until there is excess to spill back to grid. It would be helpful if we stopped running an entirely artificial timetable in winter that demands heavy activity well outside daylight hours, so that demand better matched availability.