Renovated single-family house in Austria

Heating with the sun

A renovated single-family house with approx. 190 m² has a 35 kWp photovoltaic system integrated on the roof and in the facade. With the abundant excess from the yields of the photovoltaic system, two large heat storage tanks (buffer storage) are heated during the day with the own photovoltaic power via two 9 kW screw-in heaters.



Client/Owner/Planner: Stöger family, 5 persons 
Type of building: Single-family home
Year of construction: Core-rehabilitated single-family house from the 1970s
Quadratmeter: Extension 2021, today 190 m² living space
Photovoltaic power, orientation: 32 kWp south oriented, 15° inclination
1,25 kWp south oriented, vertical in the facade
2,25 kWp west oriented, vertical in the facade

Heat storage size: 2 x 1,000 liter buffer storage tank
Used my-PV product: AC•THOR 9s, operating mode M3, 18 kW
System control by/with: my-PV Power Meter


Customer statement

The family lived in this bungalow until its enlargement and renovation in 2021. A 5.5 kWp photovoltaic system had already been installed on it before, and the AC•THOR 9s from my-PV used surplus energy to load the two 1,000 liter buffer tanks.

Even before the photovoltaic system was enlarged, the client Markus Stöger, himself a specialist in high-quality electronics, created the right conditions in his hydraulic heating system for the planned system expansion. For example, by installing two 9 kW screw-in heaters, the subsequent increase in photovoltaic heat generation capacity was already considered from the outset.

With over 35 kWp of installed photovoltaic power, it is now a true solar power plant that naturally provides immense excess power. These surpluses from the photovoltaic system can be used sensibly on site for heat generation thanks to my-PV's solutions, instead of being unprofitably fed into the grid.

In the new 18 kW operating mode, two electric heating elements are supplied with surplus power from the photovoltaic system. One of them can be controlled continuously, the second one is switched on as soon as sufficient surplus is available.

Since both 9 kW heating rods were already available, the effort to upgrade the photovoltaic heating was limited to the installation of a three-pole relay and a minimal adjustment in the wiring. The necessary firmware update for the AC•THOR 9s was simply imported by my-PV via the Internet. All AC•THOR 9s already installed by our customers can also be made suitable for this operating mode by updating the software.

In addition to the surplus detection at the house connection point by means of my-PV Power Meter, Markus Stöger uses (as an optional extra) a second my-PV Power Meter for power measurement at the switched heating rod. Thus, this consumption is also shown in the power display on the display and on the web interface and can also be taken into account in the energy recording of the data logger.



In this operating mode, it is expressly recommended that both the AC•THOR 9s control and the power measurement at the switched load are each carried out with a my-PV Power Meter!

Enormous advantages for the customer

The AC•THOR 9s has been in use in the new operating mode since summer 2021. By mid-November, it had not been necessary to heat up the biomass heating system even once, and this despite the fact that the existing high-temperature heating system with radiators was retained on the first floor during the refurbishment.

The immediate economic benefits are already obvious. The costs for the chimney sweep have been significantly reduced and the storage space required for logs has also been massively reduced. Both in front of the building and inside it. In the future, the family will have an entire basement room at its disposal, once the existing firewood stocks have been used up. Whether this will happen in the coming winter is highly questionable, however, because the heating season for the Stöger family has now been reduced to the months of December and January thanks to photovoltaic heating from my-PV.



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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