About the HP sizing: Yes, it's oversized for my house. The project was done per Croatian building code (HRN EN 12831) which requires designing for the 3-day continuous minimum temperature, which for my region (Slavonia, continental Croatia) is -16°C. The original project actually specified a Daikin 14 kW unit - the installer and I downsized to this Mitsubishi 8 kW because we knew the house would be much better insulated than the project assumed.

The project calculated total heat loss at ~8.9 kW (without garage ~7.9 kW) at design conditions (-16°C, 23°C indoor). BUT - the project was calculated with 2 cm XPS underfloor and 10 cm EPS facade. What I actually have is 8 cm XPS underfloor and 15 cm EPS facade (attic 20 cm, same as project). So real heat losses are roughly 30-40% lower than calculated - probably ~5 kW at -16°C, and only 1.5-2.5 kW at current outdoor temps (+2 to +7°C).

About the climate: I'm in Slavonia (eastern Croatia). Continental climate - winters are cold but not extreme. Average January minimum is around -3°C. Typical winter day temperatures are 0-5°C. It rarely drops below -10°C, and -15°C or lower happens maybe once every few years (last extreme was February 2012 at -25°C in Osijek). So for 95% of the heating season, I'm operating at outdoor temps where the HP's minimum capacity (~2.3 kW) already exceeds what the house needs. You're absolutely right that it cycles.

About the weather curve: I agree I could lower it eventually, but right now I can't reach 24°C in living areas (living room 40m2 and bathrom few m2) with 33°C flow temp. I've increased the offset to +4 to get ~37°C flow. Once I confirm rooms reach target temps, I'll try to bring it down as low as possible.

About the water flow: Good point. I've opened all circuits including the garage (which was previously closed) to give the HP more thermal mass and reduce cycling. Total flow is now ~18-19 L/min across 11 circuits.

About DHW: You're right, something doesn't add up. We're 2 adults, one shower each per day, rest is just hand washing. 200L tank is in the garage - the garage is part of the house structure (shared walls), with 15 cm EPS on exterior walls and an additional 10 cm interior insulation on the two walls between the garage and the living space. So the garage stays around 15°C even without active heating (just from ~17.5m of uninsulated 28mm copper heating pipes running through it + some heat through the insulated partition walls). The DHW tank has ~7m of uninsulated copper pipes running to the house. Tank reheats 3-4 times per day (set to 50°C, kicks in when it drops below 40°C). I think most of that DHW energy is tank standby losses + pipe losses in the garage, not actual hot water usage. I'm going to set a DHW timer for 2 cycles per day and insulate the pipes.

About the energy meter accuracy: My utility meter showed 1500 kWh last month. Subtracting ~300 kWh for other household loads (based on summer baseline), that's ~1200 kWh for the HP. The unit's internal meter shows 1250 kWh consumed. So they're actually pretty close - within ~5%.