The installment payment is initially secondary, as the final settlement is done at the end, and then you either pay extra or receive a refund. The construction electricity needed for the regular work (stone cutting, crane, drilling machines, etc.) is not that much. For us, it was a total of €360, and we paid 28 cents per kWh.
Construction drying and heating the house are really energy-intensive, and it depends on what you use for heating. We already had electricity in the house and then ran the construction dryers on house electricity (4 cents less per kWh). There were four construction dryers and four fans running for three weeks. That consumed 1,500 kWh, so about €375. We heated the construction with our gas condensing boiler. The price difference here is enormous: for the kWh of gas, we paid 4.5 cents, whereas for electricity we would have paid 25 cents, almost six times as much.
Our neighbors had to heat the house with a high-power electric instantaneous water heater, and that in the middle of winter. They ended up spending over €3,000 on electricity.