£9bn due to not having built more cheap onshore wind, £5bn due to poorly insulated homes, £5bn due to low solar deployment, £3bn because new homes were built less efficient.
Ah, but then you’ll have to put up will all the folks whining about new builds, and that a waste outlet pipe wasn’t connected properly, Vs a 60-70s that’s still standing so must be much better, as long as we ignore the black mold in the cavity that is slowly killing us.