AC•THOR in a multi-family house
Heat generation using PV surplus in the Lavant Valley
Nestled in the picturesque Lavant Valley, a renovated multi-family home demonstrates the full potential of solar power.
Facts about the project
- Planner/Installer/Owner
- Location
- Photovoltaic output and orientation
- Inverter, battery storage
- Heat storage size
- Building type
- Year of construction
- my-PV product
- System control
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Optimal Conditions for PV Heat: Successful System Upgrade in the Lavant Valley
Nestled in the picturesque Lavant Valley in southern Austria, a renovated multi-family home demonstrates the full potential of solar power. The 11.25 kWp PV system on the roof generates more electricity than the household consumes – even with a battery – creating ideal conditions for solar-based heat generation.
Originally built in the 1960s and extended in 2011, the 250 m² home now accommodates a family of three plus two additional residents. In 2023, homeowner Michael R. decided to replace the outdated oil heating system with a modern pellet heating system. Previously, oil consumption had ranged from 2,600 to 3,000 liters annually—before installing the PV system. He chose a 15 kW Fröling pellet boiler with a 500-liter buffer tank and a separate 300-liter domestic hot water tank.
The PV system includes 30 modules: 12 installed on a flat roof with east-west orientation, and 18 on a south-facing pitched roof. This thoughtful setup ensures a balanced yield throughout the day.
Personal customer opinion and resumee
“The entire system has been running smoothly so far, and we’re thrilled to be making a real contribution to climate protection. We produce around 12,000 kWh per year and save approximately 5.3 tonnes of CO₂—an excellent setup!” the homeowner concludes.
How was the way to my-PV?
Michael R.’s goal was to avoid feeding surplus PV power into the grid at low compensation rates. Even after charging his 10.8 kWh neoom battery, plenty of solar energy remained. The solution? Use the surplus to generate heat.
Following a recommendation from PV provider Enerix Solar, the homeowner opted for the AC•THOR, the photovoltaic power manager for continuously regulated heat output. In its special M2 operating mode, the AC•THOR can control two heating elements one after the other—either in stratified charging mode or in two separate storage tanks, with priority given to the buffer tank. In this case, one element was installed in the 500-liter buffer tank, the other in the 300-liter domestic hot water tank.
Thanks to the open system architecture of my-PV solutions, integration into the existing system was straightforward. Both the battery storage and the BEAAM IoE Gateway used for system control are from neoom, one of my-PV’s 80+ compatibility partners. This allows the AC•THOR to receive real-time surplus data and start generating heat as soon as the battery is fully charged.
Installation of the device
In summer 2023, the system was expanded to include two heating elements and the AC•THOR. The technically skilled owner handled installation and commissioning himself—with support from my-PV, which he described as offering “excellent advice.”
Household and hot water demand
The AC•THOR now precisely controls the heating element in the 300-liter hot water tank, ensuring that domestic hot water for all five residents is almost entirely generated from PV surplus. The optional hot water backup function remains disabled—if needed, the pellet system steps in.
In addition, the AC•THOR provides heating support: in transitional seasons it supplies comfortable room temperatures with PV surplus, and in winter, the heating elements assist the pellet boiler.
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Conclusion: PV surplus put to good use
In its first year of operation, around 2,100 kWh of surplus PV electricity was efficiently converted into heat. Michael R. is highly satisfied – with both the savings and the environmentally friendly use of his self-generated power.
“The entire system has been running smoothly so far, and we’re thrilled to be making a real contribution to climate protection. We produce around 12,000 kWh per year and save approximately 5.3 tonnes of CO₂—an excellent setup!” the homeowner concludes.
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AC•THOR
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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