Hot water from photovoltaics for the employees

Reference project 3 Phases Czech Republic

A Czech manufacturer of measurement technology secures the hot water requirements of around 15 employees with the photovoltaic heating solutions from my-PV.





Client: Comac Cal s.r.o.
Location: Těrlicko, Czech Republic
Construction type:

Commercial building, new production hall of the company Comac Cal s.r.o

Year of construction and number of square meters:

2020, 330 m²


20 kWp

Heat storage size:

300 liter boiler

my-PV product in use:

3x AC•THORs, benefit lies in the use of self-generated PV energy for boiler heating for showers.

System control by/with:

my-PV Power Meter (predecessor to my-PV WiFi Meter)


Customer declaration

How did you come to my-PV?

The Czech company Comac Cal s.r.o., which operates in the field of measurement and sensor technology, is using the solutions of my-PV in its newly built company building.

The company came across the products of my-PV through the German company E3/DC GmbH, a producer of household energy storage systems. The PV market in Czech Republic is, similar to other European countries, characterized by low feed-in tariffs of photovoltaic energy. The most efficient and cost-saving way to deal with these circumstances is by increasing one’s self-consumption of the PV energy generated. my-PV products represent the ideal solution by using PV energy to generate power, hot water and heating instead of feeding it into the public power grid.  


Obstacles/specialities during the installation

The LAN network within the company posted a challenge as it blocked the internal access to the power meter’s parameter. Apart from that there were no difficulties regarding the installation of the AC•THORs and the my-PV Power Meter.


Brief explanation of the system – what should be mentioned?

The system is used to heat water in the boiler with a volume of 300 liters to supply the showers for the employees in the company building.

In Czech’s 3-Phase grid, each phase L1, L2, L3 demand & supply of electric power is separately billed, uses phase measurement method (not summative).

A requirement of this 3-phase connection is the simultaneous regulation of each phase in contrast to the typical approach with sum of consumption & PV-power export on all 3 phases as in a German power grid. The reason for this is that the grid operator charges per kWh unit consumed and exports separately on each phase.

For this reason, it is important to regulate each phase separately, which is possible with the three single-phase AC•THORs. As both, the generation of PV power varies during the day as well as consumption fluctuates on each phase, the 3x AC•THORs manage the surplus power simultaneously on each phase by diverting it to a 300-litre electric boiler.

With the linear power control of each single-phase AC•THOR from 0 to 3,000 W, each surplus watt is instantly and efficiently derived.  

In this project, each AC•THOR is connected to 2 kW immersion heater. In general, 3xAC•THORs can carry out power regulations of 0 to 9 kW. Here the question may arise why AC•THOR 9s isn’t used instead of 3 times the AC•THOR, a 0 – 9 kW linearly controlled photovoltaic power diverter that can control 3-phase heating elements up to 9 kW?

The simple answer to that question is the client’s wish to optimize each phase as Czech’s power grid requires each phase regulation, while each AC•THOR is connected to a heating element. Here AC•THOR 9s even though it is 3-Phase device but it will not be optimal in this project because AC•THOR 9s diverts only sum of excess power on all 3-phases. It is also worth noting that when a three-phase load is connected to 3x AC•THOR, galvanic isolation is necessary for the star connection. Each load is separately connected to each AC•THOR.


Persons in the household - hot water requirement?

Since it is a commercial building, the hot water demand of all 15 employees of Comac Cal s.r.o needs to be covered.


Is hot water backup with mains power used?

Yes. The provision of hot water is entirely centralized in the building and is used for showers by company employs. To ensure a minimum temperature of the hot water, a backup power is also activated on the web interface setting of all 3 AC•THORs.


Personal customer opinion and resume:

The customer is very satisfied with the system. Thanks to the AC•THORs in use, each watt that is used for water heating and produced with PV power pays off, as otherwise the PV power would have been exported to the power grid for an extremely low feed-in tariff.


my-PV GmbH
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A-4523 Neuzeug

+43 7259 39328

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About us


We at my-PV get more out of photovoltaics than just electricity, we move your building technology into the future. Use your solar power yourself instead of feeding it into the public grid: Electricity, hot water, heating and charging options for your e-car. With our products, you can use your self-generated photovoltaic electricity for your own needs without any detours. This way, you save costs in the long term and act environmentally friendly!



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