A solar-electric apartment building project in Graz

Hot water and heating with solar energy

In the south of the Styrian capital, 8 apartments are heated and supplied with hot water with surplus from the photovoltaic system.



Project management: Manuela Reiner, Enoiko GmbH (Project coordination)
Martin Reiner, EAM Asset Management GmbH (Contracting)
Building type: New construction, apartment building, hot water demand at location: 36 kWh/m²a
Year of construction: 2021, 495 m² net floor area

Square meters: 8 condominiums, each between 50 and 70 m²
PV capacity and orientation: 64 kWp in total
On average 2 x 3,5 kWp per apartment placed on the roof (east/west oriented, 10° inclination), as well as on the carports (south oriented, 15° inclination)

Size of heat accumulator: Common electric suspended storage tank from Austria Email, 150 litres, heating capacity 2,3 kW
my-PV product used: AC•THOR 9s, Operating mode M5: Hot water and space heating
System control: my-PV.LIVE Cloud Connect as central control of the entire heat generation


Customer declaration

How did you find out about my-PV?

The customer first came into contact with my-PV several years ago, at the trade fair “Intersolar” in Munich. At first, Martin Reiner only informed himself about the possibilities of the my-PV solutions at that time. When the my-PV product portfolio subsequently included additional areas of application, such as solar-electric space heating, he contacted us again via the website.


Challenges/particularities regarding the implementation?

During the first stages of the joint planning process, on the part of partner companies, there was initial scepticism regarding the new “photovoltaic heat” technology. In the beginning, for the planners and construction supervisors, the solar electric concept represented something entirely new. In a joint meeting of all those involved, however, the concerns were quickly dispelled. my-PV provided support in advance, with a detailed technical simulation and a forecast of the expected operating costs. The ecological, technical and economic advantages of the concept "cables instead of pipes" are quickly convincing for experienced construction companies.

The tenants were unreservedly accepting towards the concept and even the authorities had no difficulties concerning permits, not even regarding electric heating!


Brief explanation of the system – what should be mentioned?

In the eight-party house, one AC•THOR 9s per apartment uses excess energy yields from a large, grid-connected photovoltaic system for decentralized water heating in the apartments as well as for electric space heating. Only the my-PV technology ultimately makes the electric heat generator suitable for photovoltaics. Our fast and precise power modulation makes them "PV-ready". Missing energy, for example during winter, is drawn from batteries and the public power grid.


Persons in the household – demand for hot water, etc.?

On average, one apartment is occupied by two people. This results in a hot water requirement of around 100 litres per day. There are always reserves in the 150 litre hanging tanks, and there is also an additional day storage volume for PV excess.

Moreover, there are no additional costs for tenants. "Housing costs are either in the usual market segment or below," according to the customer.


Is thermal backup used with grid power?

Yes, because there is no other heat source. The building technology is extremely simplified by "cables instead of pipes". In times when there is not enough solar radiation, the automatic thermal backup comes into effect for both hot water and room heating. Primarily electricity from the batteries is used (storage capacity 5 kWh per apartment) and only at a later stage, electricity is drawn from the public grid to ensure comfort. Most of the year, however, this is barely or not at all necessary.


Customer opinion and feedback

For this new project near Graz, my-PV technology for the first time by the developer. So far, conventional hydraulic systems such as ground or air heat pumps, gas, oil or district heating have always been used in building services. In addition to the drastic simplification of the system technology, the areas of electricity, hot water and space heating can now be combined for the first time through sector coupling.

The technology is very economical in operation. A first positive balance can be drawn up regarding the months of March to June 2021. During this time, in one apartment just 100 kWh per month were drawn from the public grid to provide electricity, hot water and space heating. The by far greater part of the energy came clean and free of charge from the internal photovoltaic system; and this despite the fact that the heating season was still ongoing during this observation period. The builder Martin Reiner describes this as “top values”.

Due to the battery storage used, the initial investments were slightly above the level of conventional building technology. However, since solar-electric heat can be realized problem-free without battery storage with my-PV, the property developer is free to decide whether he wants to save additional installation costs. Thus, the construction costs would also be below those of hydraulic building installations. Higher operating costs very unlikely if the batteries are left out.


Concluding statement from Martin and Manuela Reiner: The my-PV technology is easy to implement and is already planned for the next projects. After initial discussions, once the concept has been understood by everybody, the question arises: “Why doesn’t everyone do it this way?”

Would you like an insight into the project?

We also accompanied the project with a video - you can find it here.

EAM Asset Management GmbH
Lagergasse 380 8055 Graz

Enoiko GmbH
Lagergasse 380
8055 Graz


my-PV GmbH
Betriebsstraße 12
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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