ᐅ Is a multi-split air conditioning system suitable for heating?

Yes, the pellet price is definitely correct
(putting aside the free photovoltaic power, especially since it can only be considered in the calculation during the day and in summer).

So pellets would still be the preferred option; I just need to figure out how to set up a pellet storage bunker somewhere to avoid dealing with the hassle of bagged pellets.

guckuck2 schrieb:

The biggest disadvantage and perhaps the main reason why air-to-air heat pumps are not particularly appreciated even in new builds is the heat transfer through air. It’s simply quite uncomfortable.

Radiators do this as well with their supply temperature. Most of the heating there is by convection. Advantage: somewhat quieter.

guckuck2 schrieb:

The mentioned air is also quite dry.

Since the system does not dehumidify during heating, the (absolute) humidity of the air does not change.

I wouldn’t dismiss the plan right away and would initially install a single-split unit on each floor. 2.5 to a maximum of 3.5 kW is more than sufficient. Single-split units are cheaper and more efficient. Place the indoor unit as centrally as possible, or where it should be warmest. Heating about 60 m² (650 ft²) per floor with one unit works well if doors are left open and, as mentioned, it runs 24/7. This can also operate efficiently at least down to an outdoor temperature of -5°C (23°F).

It is important to avoid starting the pellet heating system as long as possible. This is similar to a car: starting the boiler accounts for most of the energy loss. The worst for the pellet stove is the daily start in summer for about 20 minutes of hot water production. This can also be addressed with solar thermal (ST) or a heat pump water heater (HPWH).

Addition: To try it out, you can start by installing an air conditioning unit only on the occupied floor. This costs around €3500 (about $3700). Leave out the radiators on that floor and see how it works. In the worst case, you end up with a comfortable summer.

kati1337 schrieb:

Sure, you could have easily kept it warm that way, but you could also just as well sit in front of the electric meter with a bowl of popcorn.
It was simply really expensive. So, we only turned the units on as long as it was absolutely necessary.

If you can't afford heating in winter, then you can't afford cooling in summer either. It uses just as much energy. So why did you install those three units in the first place?

Deliverer schrieb:

Additional note: To try it out, you could initially just equip the inhabited floor with an air conditioner. That costs around €3500 (about $3700). Leave out the radiators on that floor and see how it goes. In the worst case, you’ll have a comfortable summer.

There are very good air conditioners available for €500-700 (about $530-$750), and good ones already from €300 (about $320). You can install it yourself or know someone who knows someone…

I know someone who orders cheaply from Italy and can’t get these prices. Doing it yourself is prohibited in Germany and not exactly straightforward. If you have it done by someone else, you pay €1000 per kW. Currently probably more.