Air-to-water heat pump - Nest Thermostat

Even here I can only agree once again... your thermostat throttles your room while you cook and 1-2 hours later, when you have long been gone, your kitchen cools down...

You didn’t save anything during that time... because the heat came from the stove and the floor was throttled... now the floor has cooled down and needs to be reheated to the set point by using additional energy... so your heating turns on again and heats for 1-2 hours until the room is warm again...

The same with the fireplace and solar radiation...

That's not true at all. If I've been cooking for an hour, that corresponds to the heating energy of many hours for this room, and with the fireplace and sunlight, it's even more extreme. Nothing cools down here at all, because after a few hours the EER opens again, and the supply temperatures are very low (the floor takes many days to cool down, there's an incredible amount of energy stored in it! Such nonsense in your argument!). The floor hasn't cooled down significantly because the energy the room needed was provided from elsewhere. Precisely because of the inertia of underfloor heating, the EER can save energy! You shouldn't imagine underfloor heating like a radiator that radiates energy into the room through actual heat, but rather provides a few watts of heating power very dosed! Even at -20 degrees outside temperature, my kitchen/dining area needs less than 700 watts of heating power, so at 0 degrees there shouldn't still be an additional 500 watts of solar radiation causing extra energy from the underfloor heating that I then have to air out.

With the fireplace and the sun, you haven't brought any argument at all. Most heating systems operate based on outside temperature + return temperature control and don't notice the countless kWh from the sun and fireplace or only do so much too late. Because of this control, the heating doesn't kick in 1-2 [hours] later as you (Mycraft) say and then have to heat something back up. An underfloor heating system doesn't work like that (especially not that quickly).

Does that mean a fireplace does not relieve an air-to-water heat pump at all in winter?

Because you overestimate them or they are noticed through the return flow if they were that strong – which I still can’t quite imagine in winter.

And a fireplace is a special treat that normally has no place in a modern house. I also ordered one because I don’t care and I can still open a window without fear.

But you haven’t understood how the individual heat carriers and above all the hydraulics of underfloor heating work and what a thermostat messes up with it.

By the way: I planned an exhaust hood – crazy, right?

I know of 4 houses with heat pumps from my private circle that each have thrown out the ERR – and strangely not only save noticeable electricity but also no one dies from heat. That’s theory and practice...

The topic has been beaten to death so many times and everywhere... anyone who understands the technology knows that ERR brings nothing in a modern house...

and I can speak from experience... 3 years without... not heating the heat carrier at all, that’s where the savings are, not in shutting down individual heating circuits...

@Bautraum 2015
Yes, a fireplace brings nothing except romantic atmosphere and sauna feeling, well and afterward, of course, dirt...

Sauna feeling? Cool, I want that! A stove is needed!