It’s not the only reason. I’m literally a mechanical engineer (by degree, not trade) and tried to get an air-to-water heat pump to replace my aging gas boiler.

Only one firm in the area could even quote me on one, tried to talk me out of it at every step, and gave me a quote that reinforced their sales pitch. It was literally never going to payback over a combi, which dozens of companies would be happy to install and service.

So, a fresh combi boiler sits on my wall (which is a good improvement over the old), but it also means that I don’t entertain the question again for another 15 years.

I was among the top 0.1% aware, educated, and motivated potential customers of a heat pump and it couldn’t happen.