The author calls it a heat pump, and I'm not saying he's wrong, but when people think of heat pumps, they either think of a system that has some amount of pipin

The author calls it a heat pump, and I'm not saying he's wrong, but when people think of heat pumps, they either think of a system that has some amount of piping buried in the ground or it has a unit that sites outside (and is generally reversible so it provides air conditioning in the summer) such as what is shown int his image: https://www.alliedmarketresearch.com/assets/sampleimages/heat-pump-market-2019-2026-1588240429.jpeg https://www.alliedmarketresearch.com/assets/sampleimages/hea... And it looks like the unit he has (assuming I've found the right one) uses a heat pump for producing hot water, but for heating the home it would often be paired with an external heat pump: https://www.nilanuk.com/domestic-solutions/compact-p/ https://www.nilanuk.com/domestic-solutions/compact-p/