Battery storageElectric heatingMonitored consumption

Detached House, Vejvanov

A 19th-century stone house in Vejvanov is heated – with significant savings – by a radiant heating system combined with a photovoltaic system and a battery.

Heating matsheating filmsradiant panelsconvectorsHES battery storage systems

The house, comprising two flats and an extension dating from 1980, has a high heat loss of 32.5 kW and an annual energy consumption of between 21 and 29 MWh. Instead of extensive insulation or installing a heat pump, the owner decided to reduce costs in a different way – the aim was to lower the unit cost of energy whilst retaining the existing electric radiant heating system.

Summary data on electricity consumption and costs from previous years are available:

Period	NT consumption (kWh)	Summer 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
2024	SPOT – NT/VT not monitored		26,984	78,646	2.91
2025	SPOT – NT/VT not monitored		30,273	84,794	2.80

^*) Amount of energy consumed affected by the commissioning of the PV system

From January 2024, the property switched to a system of buying and selling electricity at spot prices (optimised by an algorithm within the HES storage system); more detailed monthly statements have been available since then:

Period	Total consumption (kWh)	Off-take from the grid (kWh)	PV system generation (kWh)	Feed-in to the grid (kWh)	Consumption from the grid (CZK)	Feed-in to the grid (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	3,234	2,731	656	153	16,365	623	15,742	4.87
12/2024	4,751	4,210	591	50	24,328	225	24,103	5.07
Total	26,984	17,208	17,502	7,726	92,198	13,552	78,646	2.91

^*) External inverter with 10 kWp PV system switched off
Prices include VAT.

The results for 2024 show that a PV system with HES battery storage, effectively managed in line with spot price trends, is capable of achieving average prices corresponding to those seen in 2016/2017.

Period	Total consumption (kWh)	Off-take from the grid (kWh)	PV system generation (kWh)	Feed-in to the grid (kWh)	Consumption from the grid (CZK)	Feed-in to the grid (CZK)	Electricity costs (CZK)	Achieved price (CZK/kWh)
01/2025	4,385	3,821	622	58	20,731	228	20,503	4.68
02/2025	4,378	3,201	1,374	197	18,407	419	17,988	4.10
03/2025	3,509	1,708	2,388	587	8,983	579	8,404	2.39
04/2025	2,058	659	2,243	844	3,492	840	2,652	1.28
05/2025	1,439	144	2,504	1,209	1,542	1,444	98	0.07
06/2025	1,027	70	2,444	1,487	1,346	2,772	-1,426	-1.38
07/2025	1,026	83	2,413	1,470	1,404	2,889	- 1,485	-1.44
08/2025	1,064	105	2,876	1,917	1,354	2,603	-1,249	-1.17
09/2025	1,043	254	1,912	1,123	2,012	2,612	-600	-0.58
10/2025	2,366	1,493	1,266	393	6,875	988	5,887	2.49
11/2025	3,528	2,885	741	98	14,910	166	14,744	4.18
12/2025	4,450	3,955	537	42	19,358	79	19,279	4.33
Total	30,273	18,378	21,319	9,424	100,412	15,618	84,794	2.80

In 2025, too, very good operational results were achieved thanks to the PV system and optimised management of the HES storage facility, despite the house’s increasing energy consumption.

Period	Total consumption (kWh)	Off-take from the grid (kWh)	PV system generation (kWh)	Feed-in to the grid (kWh)	Consumption from the grid (CZK)	Feed-in to the grid (CZK)	Electricity costs (CZK)	Achieved price (CZK/kWh)
01/2026	5,072	4,654	472	54	21,797	152	21,645	4.27
02/2026	3,987	3,379	724	116	14,184	172	14,012	3.51
03/2026	2,969	1,374	2,393	798	6,216	1,184	5,032	1.69
04/2026	2,231	875	2,018	662	3,077	713	2,364	1.06
05/2026	1,355	350	2,035	1,030	1,483	2,484	-1,001	-0.74
06/2026	981	189	2 343	1 551	1 656	4 472	-2 816	-2,87
07/2026	1 022	241	2 425	1 644	1 834	4 077	-2 243	-2,19
08/2026	1 070	159	2 687	1 776	1 715	5 307	-3 592	-3,36
09/2026	-	-	-	-	-	-	-	-
10/2026	-	-	-	-	-	-	-	-
11/2026	-	-	-	-	-	-	-	-
12/2026	-	-	-	-	-	-	-	-
Total	18 687	11 121	15 097	7 631	51 962	18 561	33 401	1,79

The owner has retained the tried-and-tested electric radiant heating system and supplemented it with a photovoltaic power plant and HES battery storage. The house is fitted with a combination of ECOSUN radiant panels, ECOFILM floor and ceiling foils, ECOFLOOR heating cables and mats, and ECOFLEX convectors. The total installed power of the electric heating system is 29.2 kW.

Reference video

Homeowner's Testimonial

As a homeowner, I can say that the energy solution we chose has definitely paid off for us. The 19.8 kWp photovoltaic system is divided into two parts – one part is connected directly to the HES Battery storage system with a capacity of 41.1 kWh, whilst the other operates via a grid-connected inverter. Since 2024, we have been taking advantage of spot electricity prices, and the entire operation of our home energy system is controlled by the HES storage system’s smart algorithms, which effectively limit the purchase of expensive electricity from the grid. The house’s annual consumption is around 27 MWh, so it was important to us that the price of electricity was as low as possible. Thanks to the solution offered to us by FENIX, we have managed to bring the average price of electricity down to 2.9 Kč/kWh. Compared with the period of the energy crisis, we now save around 80,000 Kč a year, which clearly confirms that we have chosen the right path.