ᐅ New heat pump to replace oil heating with existing radiators

strzata schrieb:

estimated heating demand 58,860 kWh

That matches the oil consumption but not the 49 W/m² (4.5 W/ft²).
What heating demand and heating load figures have the competitors used?
Why install additional indoor air units if the radiators already provided comfortable warmth?

Because the heat pump is too small

Please have the heating load properly calculated for each room. Are you now forced to replace the oil heater?

The estimated annual consumption of about 60,000 kWh would imply that the oil heating system operated at 100% efficiency. Since I assume an older unit, I expect more realistically around 60-70% efficiency. The rest of the energy would have been lost through the chimney and possibly into the basement. To me, this all sounds very unreliable, and I strongly recommend stepping back and starting the process over again.

strzata schrieb:

Actually, I was supposed to get 55% funding on the total amount (some people here in Thuringia say so, I live on the top floor, with slanted walls, and the whole lower floor is rented out commercially), three separate entrances, but DWW says I won’t get that.

An energy consultant can reliably tell you that. Unfortunately, I’m not very familiar with funding conditions for multi-family houses with commercial spaces. But this has nothing to do with Thuringia specifically—this is handled uniformly across Germany by the KfW.
You won’t get the 5% environmental bonus with R32 refrigerant anyway. So the maximum is 50%.

This is stated in the counteroffer. However, I cannot interpret the dummy.

The estimated annual consumption of about 60,000 kWh would imply that the oil heater had 100% efficiency. Since I am assuming an old unit, I expect more like 60-70%. The rest would be lost through the chimney and possibly the basement. To me, none of this sounds reliable at all, and I strongly recommend hitting the brakes and starting over.

Not 60,000 kWh, but 6,000 liters of oil consumption.

Why additional indoor air units if it was comfortably warm with the radiators?

Because with the heat pump, the supply temperature is only 45 to 50 degrees Celsius (113 to 122 °F), whereas with oil heating, it sometimes reached almost 60 degrees Celsius (140 °F).

strzata schrieb:

Because with the heat pump, the supply temperature is only 45 to 50 degrees Celsius (113 to 122°F), whereas with oil heating it was sometimes nearly 60 degrees Celsius (140°F).

That’s why only a fool would switch from oil to a heat pump without making other adjustments. A smart person replaces the radiators and operates at 40-45 degrees Celsius (104-113°F) supply temperature and isn’t surprised by high heating costs, which the fool will have. 😉

strzata schrieb:

Not 60,000 kWh, but 6,000 liters of oil consumption.

That’s roughly the same. If you seriously calculate with a COP of 3.5 in your old building, that’s about 17,000 kWh of electricity. At 30 cents per kWh, heating costs remain around €5,100. 6,000 liters of oil cost roughly €500 more. So you’re basically trading high oil costs for high electricity costs.