From that paper, the average COP measured was 3.06 (averaged between 2 and 7 degree outdoor temperatures, typical of the UK).
The UK electricity price is currently fixed at 34p/kwh for electricity and 10.3p for gas.
A new gas boiler has a COP(efficiency) of 1.054 (it can manage efficiency higher than 100% because gas is metered by the 'lower heating value', which assumes the exhaust gas escapes as steam, but the boilers actually condense most of that steam to water, getting additional energy out).
So. Total price is: Gas: 10.3/1.054 = 9.77p/kwh in your home.
Total ASHP price is: 34p/3.06 = 11.1p/kwh in your home.
And this analysis ignores the fact that ASHP's typically have much worse efficiency making hot shower water (which a gas boiler doesn't), and obviously also have considerably higher upfront costs too.
However, the ASHP can also be used to cool your home in the summer. In the past this has been a dubious benefit for most of northern Europe, but heat waves have been getting stronger, last longer, and happen more frequently as time goes on. This is turning into a serious consideration.
Also, you can theoretically power a ASHP with renewable energy, while there are few if any carbon neutral replacements for natural gas.
Most boilers purchased today allow use with a Hydrogen mix, and some under development allow 100% hydrogen. Before the widespread extraction of natural gas, towns were powered with 'town gas', which is ~50% Hydrogen, so this is very much proven tech.
There are a bunch of potential ways to make green hydrogen too.
So, there very much is a path to green with a gas boiler.
Green Hydrogen has not worked out so far. It is not clear that it even has a path forward. There are a lot of people hopeful that it will be a solution in the future, but as of today it is so uneconomical that even people willing to spend more to be green don't use it.
But making green hydrogen has pretty bad efficiency. It could never compete with a heat pump using the same electricity source, even if it had an efficiency of 100%, since the heat pump has an efficiency of 200-400%.
Yeah, these can make ASHP a good idea anyway, but the grandparent was nevertheless correct saying that they don’t beat gas for heat in terms of cost in normal (I.e. not current) circumstances.
the cited paper gives the efficiency of heat pump but we’re missing multiple crucial values to get from there to a comparison of heating costs
Edit: https://great-home.co.uk/air-source-heat-pump-running-costs-...
At current average British prices of 28p for electricity and 7p for gas, and using averages for both it looks like the commenter was mostly correct.
Not 100% if the spf Gives the realistic cop
In a new build that opted to forgo any gas connection, I’d be interested in seeing the costs from the substantial infra savings and hookup savings.