> I think I'd favor a "personal allowance" model similar to income tax, where you get the first X units of energy tax free and then have to pay VAT, carbon taxes etc. on the rest of it.

I can see why this is tempting, but I think there's a better way to legislate with this, especially with that poster child.

I'm a landlord of a flat. I used to live in it before I left the UK. The EPC rating is D, so despite the double glazing it's still pretty cold in winter. I am now living in a fancy new-build in Berlin which, despite being 3 times the size of that flat, can be kept warm for 10 months of the year just by body heat and waste energy from the white goods — even with higher electricity costs in Germany, it costs less to be comfortable in this building in a T-shirt all year round (even while snow is falling outside), than to be wearing fleeces and sleeping with hot water bottles and still not be completely comfortable in that flat in the UK.

A few years back there was a proposal for legislation that would increase the requirements for all rental property to be at minimum C-rated by 2030, as I understand it this was dropped and the current minimum is F or something ridiculous like that. My agent's advice is to not do anything until the legislation is actually sorted, even though I'm happy to spend whatever to upgrade the place, because until you know what the legislation demands there's always a risk of doing the wrong work beforehand, having to rip it out and put something else in.

IMO, government should push for this kind of boost, as it has with other energy-saving and insulation-boosting measures.

My first rental after graduation was a Welsh solid stone wall construction; like the example you gave, I couldn't keep warm there even with the electric bar heater a meter from me.