Heating screed with device vs. with heat pump: costs?

Hello,

during the construction of our single-family house (approx. 130 sqm area), the screed was poured 2 weeks ago.

Our general contractor now presents us with the following choice:

1) Heating the screed (= cement screed) with a 19 kW heating device, starting in 10 days.

2) Heating the screed using underfloor heating operated by a heat pump from the installation of the heat pump in mid-October.

Our contract states that I pay for the heating costs, and that the general contractor pays for the construction electricity.
Completion of the house is according to the contract February 2023.

Option 1: According to the general contractor, I have to pay for the construction electricity for the heating device, as it counts as heating costs.
So far, I assumed that heating costs are costs so that the workers can work, but not costs for heating the screed.
If I favor option 1, I will have to bear these costs anyway, since the general contractor will also be finished in February with the cheaper option 2.

How expensive would solution 1 be for me? How expensive is construction electricity and how much do I need to operate the heating device until the screed is dry?

According to the general contractor, I can move in this year with option 1, so I probably save 1 month’s rent for the current rental apartment, i.e., about 650 euros, and avoid the risk that option 2 entails, namely that the heat pump might still not be installed by mid-October.

Option 2): If after installation of the heat pump in mid-October the heating takes place via underfloor heating, does the general contractor have to pay for the electricity required for this? Would this still run via the construction electricity meter (construction electricity is paid by the general contractor according to the contract) or already via my new private electricity meter?

How much electricity would be needed here for heating and how high would the estimated savings be compared to option 1, if I have to pay for this electricity?

Which option would you choose?

difficult to quantify. For us, it wasn’t much over the heat pump. And it was August. I would prefer option 1. Do you know when the heat pump will be delivered and installed? Can he guarantee that to you 100%? A dry screed is important to be able to carry out the further work. Therefore, my favorite would be: No. 1

Attention, just an amateur opinion: I heard from our plumber that heating the screed using a heat pump (if it is a brine-water heat pump) can under certain circumstances (due to the prolonged high energy demand) cause the borehole of the probe(s) to freeze and thus be "destroyed". However, I am not aware of these warnings with an air-water heat pump or air-air heat pump.

If there are no concerns in this regard, I would also choose option 2, it should make up about 1/3 to 1/4 of the electricity costs, right? Unless time is extremely important (floor readiness, tiles, and other subsequent trades).

Whichever option: The costs for the electricity will probably fall on you. It is always directly or indirectly for heating.

Directly via the heating device with 2 weeks of heating duration = 19 kW x 24 h x 14 days approx. 6380 kWh? = approx. 2K. But your general contractor / builder should be able to provide you with these data, at least approximately.

P.S. We gave our screed time to dry calmly (without heat pump, without electricity) ;)

Costs will probably be passed on to you anyway, I assume. But that is also relatively common. Option 2 carries the risk that the subsequent work steps will be significantly delayed, especially if it is not yet clear when the heat pump will actually be installed. On the other hand, the screed will probably dry without heating as well, although more slowly. Whether that is good, I cannot judge. Option 1 sounds expensive. On the other hand, with an air-to-water heat pump, the heating element is usually switched on during the screed program -> that is also relatively expensive. We ran the heat pump's screed program during building 1 at the time, and I think we consumed about 1100 kWh. But that was in the middle of summer. In winter, it can become significantly more expensive. Best regards

Electricity for the Hotboy is actually never included. At least with us, it was communicated from the start that it is provided on-site and that only the Hotboy is used for heating (geothermal heating, see Post #3). Since the screed is also coming up soon for us, I asked the general contractor what scale to expect. A demand of 1000 - 2500 kWh was given to me, also heavily dependent on the weather. And the construction electricity price has apparently been raised to about ~40c by EnBW. So my expectation is roughly around a good thousand. Although it also strongly depends on which heating program is run. There are some that still use high temperatures even with modern heating systems, which are not actually reached in practice. A more reasonable use of resources would of course be heating via heat pump. On the other hand, you get through your heating program a few days faster, which would also be worth a few euros to me in the current situation.

At Building 1, we ran the screed program of the heat pump at that time, and I think we consumed around 1100 kWh.
But that was in the middle of summer. In winter, it can become significantly more expensive.

Were you able to operate the air-water heat pump with a cheap private electricity contract in your solution (in my case it would still be an old contract, where I could arrange a move, for 23 cents per kWh,) or did you have to settle it via construction electricity (which is probably much more expensive? How much should one calculate?)?

A cost comparison would be interesting.

For option 1, 2000 euros were mentioned above – roughly how much would option 2 probably cost?