Maximum efficiency with AC•THOR

A single-family house with many compatibility partners

Maximizing photovoltaic power in combination: This renovated house exemplifies the effectiveness of my-PV's system openness.

Datos sobre el proyecto

Photovoltaic power and orientation
Battery storage
Heat storage size
Building type
Year of construction and number of square meters
my-PV product in use
System control

What was the journey to photovoltaic heat?

The single-family home, renovated and equipped with 151 square meters, is located just a short distance from our company headquarters, namely in our hometown of Sierning, Upper Austria. The homeowner, Christoph R., was seeking a better hot water supply from renewable energy sources. After finding that the installed solar thermal system required annual maintenance and that the vertical flat collectors on the balcony railing delivered relatively low yields in predominantly diffuse sunlight throughout the year, it was decided to utilize the surplus from the new photovoltaic system (after storage in the battery) for hot water preparation as well.

The factor of system openness and compatible partners

The photovoltaic system was commissioned in 2020 and complemented with a 5 kWh battery storage from BYD. Since the system, with its 10 kWp capacity, is larger than the battery, the battery storage gets full on sunny days even before noon – the surplus then, regarding the now significantly reduced (compared to 2022/2023) feed-in tariffs, becomes unprofitable when fed back into the public grid. Thus, the desire to make even more use of the own PV power was logical. The solution lies in photovoltaic heating, utilizing photovoltaic electricity for heating.

Opinión personal del cliente y resumen

"After installing the heating element in the boiler, the rest was a breeze. KOSTAL comes pre-configured as the control method for surplus detection with my-PV, so only the network address needed adjustment. To ensure devices communicate with each other after a network outage, my-PV recommends assigning a permanent IP address to the signal source. Once understood, the connection remains stable and reliable," states Christoph R., convinced of the benefits of photovoltaic heating with my-PV.

It is important to finely coordinate all existing components in the house to avoid unnecessary grid electricity consumption. Here, the system openness of my-PV is a significant advantage: a KOSTAL inverter, the associated smart meter, known as the KOSTAL Smart Energy Meter, in addition to a BYD battery storage and the AC•THOR from my-PV with its corresponding screw-in heating element.

To avoid the need for a separate meter for each manufacturer – which would entail additional costs – the AC•THOR from my-PV can access the surplus measurement of the KOSTAL Smart Energy Meter, thanks to system openness. This ensures that household appliances are primarily supplied with photovoltaic electricity, followed by charging the BYD battery, and only then – linearly and depending on the availability of PV power – the surplus is converted into heat. If more than 3 kW is available, the remaining small surplus is then fed back into the public grid with a minimal remuneration.

How did you come to choose my-PV?

The homeowner, Christoph R., became aware of the possibilities of photovoltaic heating due to the proximity to the my-PV company headquarters. "We also found a local electrical and heating company that installed the my-PV devices for us as end customers," explains homeowner Christoph R.

Were there any obstacles during the setup?

While the hot water boiler has its own screw-in socket for heating elements in the middle, since a significant surplus was expected from the 10 kWp PV system, the maintenance cover at the bottom of the storage tank was adapted. The heating engineer only needed to replace the existing flange plate with one with a suitable screw thread. According to my-PV, installing it at the very bottom provides more volume for heating.

Household members – hot water demand, etc.?

Two people are living in the single-family home during the week, with an additional person joining on weekends. With the 10 kWp photovoltaic system, there is sufficient surplus to meet the hot water needs for this number of occupants.

Is grid electricity used for hot water backup?

Only during the summer months, and even then, only in the afternoon, to allow the system to use PV surplus for hot water preparation during the day. Optional temperature backup is not used in winter. In winter, the pellet central heating system takes on this task alongside room heating. However, in summer, the pellet central heating system can be completely shut off, thus extending its lifespan.

What are the benefits, in your opinion, of the changes or expansion with photovoltaic heating?

"With the previously high feed-in tariffs now back to pre-crisis levels, we are only compensated with the market price for electricity fed back into the grid. This price is now roughly equivalent to the cost of pellets. For us, it's clear that retaining the self-generated energy in the house allows us to immediately save on pellets. Additionally, operating the pellet boiler at partial load in summer would be very inefficient, or the entire boiler would need to heat up just to warm a few liters of water. I prefer to use pellets when I truly need them, which is in winter," explains the homeowner, outlining his motivations.

Does the technology work?

Interested in real operational data? It's easily accessible through the my-PV Cloud. Real-time data demonstrates how well the various components work together.

To the demo access of the my-PV Cloud

Real system data of this reference project
AC-THOR Seitenansicht


in use

Simple & efficient: AC•THOR controls electrical heat sources depending on the availability of PV energy and heat demand. And that for both hot water, as well as for space heating.

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