Family House Vejvanov

Stone house from the 19th century with two residential units, an extension with aerated concrete block walls from 1980. Total usable area is 238 m². Window replacement with double-glazed insulation was carried out in 2018. The calculated thermal loss of the building is 32.5 kW.
Family House Vejvanov
Family House Vejvanov

The heating system is implemented through a combination of radiant panels ECOSUN, underfloor heating foils ECOFILM F and ceiling foils ECOFILM C, ECOFLOOR underfloor heating, and ECOFLEX convectors. The total installed electric heating power is 29.2 kW.

In October 2022, a PV system with a total capacity of 19.8 kWp was installed on the house, along with an HES battery storage system with a capacity of 41.1 kWh. The PV system is divided into two identical parts of 9.9 kWp each. One group of photovoltaic panels is connected to the HES storage as standard, while the other group is connected to a separate Fronius grid inverter directly to the building’s consumption. The excess from this part of the production is handled by the battery storage system in AC coupling mode. This part of the PV system is mainly used in the winter season to increase overall production during the heating season. In the summer of 2024, this part of the PV system was deactivated, and only the part connected directly to the HES storage was in use. The reason was to prevent unwanted feed-in during periods of frequent negative prices on the spot market.

Previous years' summary data on electricity consumption and costs are available:

Period Off-peak Consumption
(kWh)
Peak Consumption
(kWh)
Total Consumption
(kWh)
Total Payment
(CZK)
Unit Price
(CZK/kWh)
2016/2017 20 390 714 21 104 57 384 2,72
2017/2018 23 824 1 262 25 086 68 747 2,74
2018/2019 22 760 1 674 24 434 73 232 2,99
2019/2020 20 931 1 170 22 101 77 069 3,48
2020/2021 26 526 2 590 29 116 93 306 3,20
2021/2022 25 346 1 027 26 373 116 848 4,43
2022/2023 *) 21 120 3 963 25 083 156 340 6,23

*) The amount of consumed energy influenced by the activation of the PV system

From January 2024, the house transitioned to a mode of purchasing and selling electricity based on spot prices (optimized by an algorithm within the HES storage system). Since then, more detailed monthly billing has been available:

Period Total
consumption
(kWh)
Grid
consumption
(kWh)
PV
production
(kWh)
Grid
feed-in
(kWh)
Grid
consumption
(CZK)
Grid
feed-in
(CZK)
Electricity
costs
(CZK)
Achieved
price
(CZK/kWh)
01/2024 4 442 3 827 756 141 17 763 216 16 947 3,82
02/2024 3 283 2 678 722 117 11 354 122 11 232 3,42
03/2024 2 798 1 438 1 815 455 6 346 405 5 941 2,12
04/2024 2 069 556 2 248 735 3 116 364 2 752 1,33
05/2024 1 000 85 2 053 1 138 1 230 1 417 -187 -0,18
06/2024 649 226 1 030*) 607 1 719 1 654 65 0,1
07/2024 657 129 1 200*) 672 1 364 1 783 -419 -0,63
08/2024 1 100 98 2 954 1 952 1 382 3 681 -2 299 -2,09
09/2024 1 039 164 2 204 1 329 1 570 2 422 -852 -0,82
10/2024 1 962 1 066 1 273 377 5 661 640 5 021 2,56
11/2024                
12/2024                
Total 18 999 10 267 16 255 7 523 51 505 12 704 38 801 2,04

*) External inverter with 10kWp PV system turned off.
Prices are inclusive of VAT.

Preliminary results for 2024 show that the PV system with HES battery storage, efficiently managed according to spot price trends, is capable of achieving average prices comparable to those from 2016/2017.

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