And OP is right. When I've looked into it you aren't going to save any money going to a heat pump; in fact it will likely increase costs slightly.
So it really only makes sense to do when you need a new boiler. If you don't, it makes way more sense to get solar because that's also good for the environment but actually saves you money.
It's not automatically linked to rate updates. There's probably a way of automating that for Vaillant systems?
(Shoutout to ProllyInfamous, who's been making the great point that in many climates HW systems that also cool and dehumidify are a great benefit. Not here at 56N, though)
I work for homely energy which has such an offering, but fwiw I genuinely think it's a good product. It's been studied by Salford uni in their energy house lab, so if anyone's interested maybe dig into that for a more neutral verdict.
Another graph in a footnote table shows the heat pump is delivering 6x the heat of the gas boiler, which feels like it should be mentioned in the text when you say it costs 3x more.
And actually that makes the previously mentioned CO2 graph even more misleading.
Heat loss in our home is high (single skin brick), but our bills over the course of the year are on a par with having the heating running for 12h a day. They are substantially more expensive during the winter when temperatures drop below 5°C, but that isn’t noticeable when averaging the bills out over the year.
Got to do our roof in the next couple of years so solar is a natural next step for us.