ᐅ Geothermal Energy: Pros and Cons?

A 100 m (328 ft) borehole is quite deep, especially when you do it three times. In our case, the heat pump was designed for 9.0 kW, and due to mostly clay soil with relatively low extraction capacity, this recommendation was made. The "most affordable" offer was, if I remember correctly, around 18,000 something.

In the meantime, we have a gas condensing boiler plus solar thermal system and are (at least for now) very satisfied with our decision.

@Bauherren2014
This was not a criticism of your post. At that price, we would have declined as well.

Since the cost of geothermal energy is often a main argument against it, I wanted to share our figures here so users can see that it can vary. At first, we were interested in geothermal energy, but we had already ruled it out before planning and were considering a gas condensing boiler plus solar system, mainly citing the cost argument.
After our general contractor quoted that geothermal, all-in (with Vaillant pump), would cost between 13,000 and 15,000 euros, it became clear to us that we would go with geothermal after all.

By the way, my sister has also been satisfied for 14 years with her gas heating plus solar system.

I did not take it as criticism either. I just wanted to express that good planning is important.

The problem is that many general contractors/developers... (certainly not all) follow a standardized approach. For example, the heat pump is simply sized at 8 kW, and a borehole of 50 m (165 feet) depth is installed (just as an example). They don’t consider who and how many people live in the house, whether the living area is 100 or 200 m² (1,076 or 2,153 square feet), or if one person prefers 18°C (64°F) with a sweater in the living room, while another likes 24°C (75°F) in a T-shirt. The same applies to the borehole. Whether the ground is clay, sand, or rock does not interest most people, even though these conditions affect the extraction capacity and require different planning. Therefore, it is advisable for everyone to consult an independent expert to clarify exactly these kinds of issues and to determine the most suitable heating option for their individual situation.

We ourselves also know two negative examples. In these cases, the heat pump and borehole were incorrectly sized, which is now reflected in the electricity consumption.

I know what you mean.
In our case, the general contractor’s (GC's) estimate for the drilling depth and the associated price was increased, making the drilling approximately €1,500 (about $1,600) more expensive – the kilowatt capacity was adjusted accordingly – and the next larger model of the pump was ordered.

The calculation here showed that more power was needed for the square meters of living space.
Still, it’s very frustrating since we had only accounted for the (lower) costs in our financing. But we accepted this as an unavoidable cost increase and covered it from our contingency fund (as well as the additional expenses for plumbing, electrical work, and doors).

Separately, the drilling was carried out by an external company specializing in this area (they seem to be primarily contracted for geothermal drilling in our region – they also drilled for a colleague of mine with another GC).

And by the way, the sun does not cool down, but will explode in about 5 billion years. Before that, it will expand so much that it will engulf all the inner planets, including Earth.

I think this should not go unmentioned in this thread.

Hello.... We are looking for ground drilling companies for our Vaillant heat pump vwf 88/4. What offers have you received?