I totally feel for this guy. But the real crime here is successive governments that have completely failed in holding the housebuilders to account with tougher specs for new build houses.
Why the hell a 2020 newbuild house needs any space heating at all is beyond me. Should just be passive, with electric heater for the shower.
The big picture is that we are shipping great wealth to fuel-producing countries because politicians are too lazy or corrupt to insist on modern building methods and standards that are properly enforced.
Honestly, this all just seems to stem from the ASHP breaking down, and possibly being undersized in the first place.
If it as having to run on resistive the whole time, then yea, it would cost a blooming fortune.
Building regs on heat retention have also tightened by 20% since 2020, so newer builds should require less to heat them now.
What I don’t get though, is that if it was a newbuild, would it not be covered by NHBC’s warranty? Which should include the heating system, unless it is already under another warranty.