Planning/Preparation of a deep drilling

Since you are building according to the 2016 Energy Saving Ordinance, the 10kW pump is certainly oversized for the living area.

And the drilling depth anyway – a reputable drilling company will tell you the correct depth based on the heat pump’s extraction capacity and soil quality.

Without a heating load calculation, all the calculations are pointless and lead to no helpful result.

What is the best way to proceed then?

Financing requires offers and some time for evaluation/processing.
The BAFA subsidy requires an application before signing the contract.
But the calculation is only available during project development (shortly before the start of construction) ...

Renounce the subsidy in the worst case, because an improperly sized heating system will haunt you for the next 20-30 years...

Besides, the subsidy would have been eaten up anyway with the previously targeted sizes

It's just (another) disadvantage when everything comes from a single source and that person is also so uncooperative...

Guessing is pointless. Without calculation, do not make any selection. That is a fact and everyone involved should know it, especially when it comes to BAFA. They do not even accept the correction of a mistake.

Good evening,

thank you for your contributions:

10kW seems too high to me, just off the top of my head.

Since you are building according to the 2016 Energy Saving Ordinance, the 10kW pump is certainly oversized for the living area.

Are there any reliable sources on this? Before the estimate by the heating engineer with 50W/m (presumably a pre-2016 Energy Saving Ordinance value?) I have very often asked about the heating demand estimate and I would prefer not to come empty-handed again.

You can have your heating load calculated based on the building geometry/building materials. I built with approximately Kfw70 according to the 2009 Energy Saving Ordinance, which is just "standard" according to current construction practices, and also basement, ground floor, and upper floor with a few more square meters per floor, in simple geometry. With my central controlled residential ventilation, I have a heating load of just over 5kW, taking hot water into account. I installed a heat pump that provides 5.8kW at B0/W35, with the heating curve set to the lowest adjustable value. Therefore, in my humble opinion, 10kW is too much for such a construction project.

Good luck,

ultimately, after estimating the heating load and the assessment of the company Viessmann, it will be a 6kW heat pump.
Now the deep borehole driller is submitting an application to the water authority, and I have to decide whether I want to use geothermal energy for 20-30 years (costs 250€) or permanently (costs 600€).

I basically want to heat with geothermal energy permanently. But what’s the point of the option for 20-30 years?
Do you have any experience with this?

Thank you very much.