I'd love to fit an ASHP for my house, but it's a listed building so The Powers That Be won't let me, and it has no wet central heating anyway. It was all (well, four rooms) storage heating, but I replaced those with modern electric clay-cored heaters. I still have an Economy 7 meter ('cos water heating), and that apparently prevents the fitting of a Smart Meter. So, despite being smaller than the average snail's shell (ok, exaggeration - it's 780 sq ft), the leccy bills are around £200 a month.