ᐅ Air-to-Water Heat Pump: Current Consumption and Data

Including drilling, only a 1000 euro difference?
And yes, the COP for geothermal energy is rather low.

tomtom79 schrieb:

Including drilling, only a 1000 euro difference?
And yes, the COP is rather poor for geothermal.

Let me roughly calculate again in my head... The all-in drilling cost was about €7800 (including paperwork, improved grout material, sludge disposal, etc.). From that, €4500 was subsidized by BAFA and €500 was a grant from the state for the drilling.
The heat pump itself was about €1500 cheaper than a comparable air-to-water heat pump, which also requires an outdoor unit including installation.
So yes, somewhere in the range of a €1000-1500 surcharge – thanks to the subsidies.
The nice thing is that if the heat pump ever breaks down, you don’t have to spend more money on the heat source again. Hopefully, the drilling will outlast me, which I wouldn’t really expect from the outdoor unit of an air-to-water heat pump (mechanical part, exposed to weather).

Yes, the COP is not great. Maybe the integrated heat meter is also unreliable. But it can’t be entirely wrong since I have an energy meter and can roughly estimate the heat pump’s power consumption. If it runs at about 1.3 kW with 6 kW heating output, that corresponds to a factor of 4.6. But that would only be for heating mode; the hot water mode is less efficient and lowers the overall average.
The COP bothers me a bit. On the other hand, the heating costs are so low (2400 kWh per year, about €480 annually with a heat pump tariff) that any optimization attempts are basically pointless. A COP of, say, 4.8 would mean an electricity consumption of 2100 kWh per year and a saving of around €60. That would be nice, in the magic triangle of consumption costs, acquisition cost/wear and tear, and comfort, but probably negligible.

guckuck2 schrieb:

I’m doing a rough mental calculation again... The total drilling cost was about €7800 (including paperwork, improved grouting material, sludge disposal, etc.). From that, €4500 was covered by the BAFA subsidy and €500 by a regional grant for the drilling.
The heat pump itself was about €1500 cheaper than a comparable air-to-water heat pump, which also needs the outdoor unit including installation.
So yes, somewhere in the range of €1000–1500 extra cost after subsidies.
The nice thing is, if the heat pump breaks down, you don’t have to spend money again on the heat source. Hopefully, the drilling will outlast me, which I wouldn’t really expect from an outdoor unit of an air-to-water heat pump (mechanical part, exposed to weather).

Yes, the COP isn’t great. Maybe the integrated heat meter is also faulty. But it can’t be totally wrong, since I have an energy meter and can roughly estimate the power consumption of the heat pump. If it runs at roughly 1.3 kW electric power for 6 kW heating output, that corresponds to a factor of 4.6. But that figure refers to the heating cycle; domestic hot water is less efficient and lowers the average.
I’m a bit bothered by the COP. On the other hand, the heating costs are so low (2400 kWh per year, with heat pump tariff about €480 p.a.) that any optimization attempts are basically pointless. A COP of, say, 4.8 would correspond to an electricity consumption of 2100 kWh per year, which means around €60 in savings. That would be nice, in the balancing act between operating costs, purchase costs/wear, and comfort, but probably negligible.

😱
With only €1000 extra cost, it’s a no-brainer. Especially here in the south, where winters are milder and air-to-water heat pumps are less favorable.
I would have expected an extra zero there.

tomtom79 schrieb:

Heat pumps are maintenance-free. Or do you maintain your refrigerator? 🙂

Well, if the heat pump fails 10 years earlier, I consider those costs as maintenance.

The drilling costs, like all construction costs, depend on the region and the local price structure.
Additionally, it depends on the type of ground and the required depth (we have 1x120m (394 feet)).
So there is a significant location factor.

However, we also received offers such as "ground source heat pump with a €15,000 (about $16,000) surcharge." The reason for this was easy to explain: the mentioned offer was not even based on a heating load calculation, let alone a valid calculation of the required drilling. It was offered by a plumbing contractor "all from one source," but the drilling would have been done by a subcontractor from somewhere else who was not involved in preparing the offer. So it was all just rough estimation and included a large risk premium.

Since we built with an architect, it was no problem at all to get the heating system properly designed, so we could approach drilling companies with the correct heat pump model and its performance, and request drilling based on a known extraction capacity. And, surprise, that results in completely different prices.

guckuck2 schrieb:

Drilling costs, like all construction costs, depend on the region and the local price structure.
Additionally, it depends on the type of ground and the required depth (we have one at 120m (390 feet)).
So there is a significant location factor.

We also received offers such as "Ground source heat pump with a €15,000 (approx. $17,000) surcharge." How that came about was easy to explain, as that offer was not even based on a heating load calculation, let alone a valid estimate of the required drilling. It was offered by a plumbing contractor providing a “one-stop” solution, but the drilling would have been done by a subcontractor from somewhere else, who was not involved in creating the offer. So it was all just rough estimates with a large risk premium.
Since we built with an architect, it was no problem to have the heating system properly designed, so we could then approach drillers with the right heat pump model and its performance details to request a drill hole with a known extraction capacity. And, lo and behold, very different prices came out of that.

What is the diameter of the borehole?
Will steel pipes be used?