[sokoloff]

Air to water heat pumps exist that can efficiently supply flow/LWT* of 135°F, so if you can turn down your existing boiler to 135°F flow and maintain temperature in the house, you can retrofit to an A2W heat pump, which does not result in your home being festooned with linesets and covers running around the outside like plastic termite tunnels.

I also tried to switch in 2022 and found that it would literally never pay off due to the dramatically higher upfront project cost, and so a combi gas boiler now hangs on my basement wall.

* - LWT = "leaving water temp" aka "supply" aka "flow" depending on where you are in the world