Yeah, I seem to be mistaken and you are right, -25 is accurate for heat pumps for room heating. But the Nibe F110 is a heat pump water heater that works down to -10C, and Indol have a few models that says down to -12C. Still quite good!

You can also connect it through the wall so that it uses outside air for its energy. Modern heat pump technology is so good it can remain effective all the way down to -25C.

Maybe only in the US? Here in Sweden I’ve recieved no such offer.

What? How so?

How did you do joint calendars in Radicale?