Comparison of geothermal heat pump with LWW pump

We decided on an air-to-water heat pump combined unit with controlled residential ventilation. Tecalor THZ 504. We can only share experiences in a few months. In terms of price, it was about the same as the gas boiler at our general contractor due to the BAFA subsidy. Either way, we would have installed controlled residential ventilation. The gas boiler was basically included in the house price, Tecalor came with an extra charge of about €17,000. For that, we receive €10,000 from BAFA, €2,000 savings from no gas connection, and about €5,000 savings from no separate controlled residential ventilation --> for us, basically a zero-sum game. Furthermore, we hope for synergies between the unit and our photovoltaic system to increase self-consumption. How it will ultimately behave in terms of operating and maintenance costs remains to be seen. For the gas boiler in the old house, we had annual maintenance costs of about €90 and that was it.

We decided on an air-to-water heat pump combined unit with controlled living space ventilation. Tecalor THZ 504. We can only share our experiences in a few months. In terms of price, it was about the same as a gas boiler with our general contractor, due to BAFA. Either way, we would have installed controlled living space ventilation. The gas boiler was practically included in the house price, Tecalor came with an additional cost of around €17,000. For that, we get €10,000 from BAFA, €2,000 savings from eliminating the gas connection, and about €5,000 savings from omitting the separate controlled living space ventilation --> for us, basically a break-even game. Furthermore, we hope for synergies between the unit and our photovoltaic system to increase self-consumption.

How it ultimately behaves regarding operating and maintenance costs remains to be seen. For the gas boiler in the old house, we had about €90 annual maintenance costs and that was it.

I consider that unwise. If one of the two components fails, it will probably become very expensive.

I think that's unwise. If one of the two components breaks down, it will probably get very expensive.

I am also not a fan of combination units. What if the air-to-water heat pump breaks down after 20 years, but the controlled residential ventilation system is still working? Then you either replace both or have a large cabinet just for controlled residential ventilation standing around (if that's feasible).

There are a few air-to-water heat pumps that achieve a seasonal performance factor of 4.5. For example, we will install the CHA-07 from Wolf. With that, we achieve a seasonal performance factor of 4.6.

At first, I wanted to say that I can't quite believe that, but then I just saw the "will" when quoting. So it is not an experience value. According to the datasheet, the mentioned pump has the following COP: A2/W35 4.54 A7/W35 5.47 A10/W35 5.88 A-7/W35 2.73 I have illustrated this graphically here: Now consider: when does your heating need to deliver the most power? At 10° outside temperature or at <0° outside temperature? In the overall consideration of the seasonal performance factor, the operating power consumption (circulation pump, fan, electronics, etc.) is also included. Therefore, the performance factor deviates more from the efficiency (COP) in warm transitional months and could theoretically even drop below 1.

And?
With all heat pumps, the efficiency decreases the colder it gets.

Decisive for the subsidy is what the [Jahresarbeitszahl Rechner] outputs.

COP and calculated annual performance factor are theoretical values. The fact is, however, they are always getting better, at least in the lab. Practice remains to be seen, the models are too new. Maybe it is also time for BAFA to adjust its criteria.

This is the case with all heat pumps that the efficiency decreases the colder it gets.

Yep. But you can use heat sources that do not (as much) undergo seasonal fluctuations. And are especially inefficient exactly when they are particularly needed. But that depends on the region and the winter.

In the last heating period, January 2020 was the month in which we consumed the most heat energy in the house. 1641 kWh heat including hot water. With a performance factor (including pumps and controls) of 4.69 or 350 kWh electricity. If I consider that a common air-water heat pump might have achieved about 3.5, that would have meant over 30€ more electricity costs that month to heat the house. And we had five such months this season...

In the last calendar year, I kept a four-person household including hot water warm on 200 sqm with 2200 kWh electricity. That corresponds here to about 572€ per year, or 48€ per month using household electricity (no heat pump tariff). Although that is not entirely accurate since part of the consumption comes from our own photovoltaic system, so actual consumption costs are a bit lower. Maintenance costs 0€.

I am therefore still very satisfied with a brine-water heat pump using drilling.