I have one of these: https://cta.ch/en/private/products/ah-i-eco-innen
I got it in October so most of the time I've had it has been <10C. It's produced 806.3 kWh of heating for hot water and 6587.2 kWh for the floor heating. It consumed 302.7 kWh and 1801.4 kWh respectively, for a COP of 2.66 and 3.66.
Personally, I prefer an air-source heat pump hot water tank. It significantly dehumidifies my basement.
That's why they're so great for warm climates though. The water heater also cools your house, especially as that heat is then lost down the drain. Everybody in the south should be jumping on these.