These are the things that are supposed to replace gas boilers.
In fact our government have pledged to put them in 600,000 houses a year by 2028 as part of the net-zero carbon emissions by 2050 project.
There are a few problems though. These things cost circa five times what a gas boiler costs. They produce lower temperatures than a gas boiler. They take up more space and they are more disruptive to install. At the moment customer demand for heat pumps is low - understandably. At the current rate of installs it will take until 2057 to install 600,000 heat pumps a year, not 2028.
Lastly there are only 1,200 tradespeople in the UK who can install heat pumps. Heat pumps take longer to install than gas boilers, a lot longer. But the government's target of 2028 would mean these tradesmen would have to install two heat pumps every day, 365 days a year, to install 600,000 per year.
Not going to happen, is it?
It's easy to set "ambitious targets" but another thing to meet them.
And this is before you wonder if we actually have the grid capacity to cater for the increased demand for electricity.