Spotted a few upright fridge/feeezer size units outside houses in Japan but plumbed in, often next to the outdoor heatpump fan unit. They’re for hot water as I suspected, using CO2 as the refrigerant for high temps - the Eco Cute CO2 heatpumps (from multiple manufacturers) has sold over 10 million units in its first 24 years on sale!
https://www.coolingpost.com/world-news/japanese-ecocute-shipments-pass-10-million/ #Heatpump #ASHP #HotWater