Reduce gas consumption with SOL•THOR
Single-family home saves gas with autonomous heat generation from PV energy
No gas boiler needed: Single-family home in Baden-Württemberg supplied autonomously with photovoltaic heat until mid-November
Facts about the project
- Owner
- Planner
- Photovoltaic capacity, orientation
- Number and type of modules:
- Thermal storage size
- Building type
- Year of construction and floor area
- Installed my-PV product
- Heating element
- System control
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Renovated single-family home without a solar thermal system?
A renovated single-family home built in 2004, but with very good thermal insulation, is located in Nellingen in the German state of Baden-Württemberg. The owner, Edwin Jersak, was faced with the problem that his existing Elco gas condensing boiler began to cause issues in 2024 — spare parts were no longer reliably available, and a new heating system was recommended.
“After extensive research, I decided on a system from Paradigma: an 800-liter buffer storage tank, heating circuit, fresh water station, and a gas condensing boiler from Viessmann. According to the quotation, the thermal charging was supposed to be done via solar thermal energy. I didn’t want that — it’s too maintenance-intensive,” Mr. Jersak explains when describing the heating system upgrade. His goal was to replace solar thermal with a much simpler solution — essentially a summer hot water guarantee.
His approach: heating the Tuxhorn tubra-eTherm C9+ electrothermal station using photovoltaic electricity. He planned to implement the necessary control systems and setup himself. For this, he additionally required 12 solar modules rated at 455 Wp each. The PV system, installed without an inverter, operates autonomously — meaning without grid connection approval or fees — and is used exclusively for heat generation. It is therefore truly the equivalent of a solar thermal system, but with significantly reduced complexity and material requirements.
The solar power was to be used for heat generation. To achieve this, the owner independently procured two units of the so-called SOL•THOR from my-PV, the Austrian specialist for heat generation from photovoltaic electricity. The proposed solution was then accepted by the heating installer, who followed the homeowner’s suggestion.
Personal customer opinion and resumee
“For us, this is the perfect heating system. With the two SOL•THOR units from my-PV, power generation is uncomplicated since no grid registration is required. The gas boiler only needs to be switched on for heating in winter. Even during the heating season, solar heat will provide very good support — at least that’s what I hope.
We have very good insulation, almost suitable for a passive house. Of course, we’ll only be able to present final data in a year-end review — but the results so far have definitely convinced me,” says Mr. Jersak, owner of the 160 m² single-family home.
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Why was the homeowner convinced by my-PV?
“I had looked around beforehand and came across my-PV through a Google search. My idea was to use a PV system to heat a buffer storage tank with heating elements. Friends had a similar system, but with vacuum tubes or solar thermal from Paradigma. I wanted the same setup, but powered by photovoltaic electricity. That’s how I found the SOL•THOR via Google,” summarizes Edwin Jersak.
But what exactly is the SOL•THOR? The SOL•THOR is a DC power manager. The MC4 connectors of the PV modules (between 1 and 10 modules, depending on input voltage limits) are connected directly to it. From the SOL•THOR, a conventional heating element, electric boiler, or essentially any resistive load up to 3.6 kW can be controlled. The direct current from the PV modules is used directly and delivered to standard AC heating elements. Up to two heating elements can be continuously modulated.
“The concept immediately excited me. Controlling heating elements in the buffer storage tank with generated electricity — without any grid registration,” enthuses the resourceful Baden-Württemberg homeowner. He also found an excellent YouTube video demonstrating the implementation. Through a webinar on the my-PV YouTube channel explaining the advantages of joint commissioning with Tuxhorn, he reached the following conclusion: “It’s extremely important to optimize the stratification in the buffer storage tank so that the maximum amount of solar power can actually be stored as heat. That’s why I decided against heating elements directly in the buffer tank and instead opted for a combination with the tubra-eTherm C9+ electrothermal station from Tuxhorn,” the homeowner explains.
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Were there any obstacles during implementation?
“I use two SOL•THOR units. With these, I control only two heating elements in the Tuxhorn electrothermal station; the third one remains unused. This gives me 3 kW of thermal output per SOL•THOR — so 6 kW of heating power in full sun,” explains the homeowner.
“One issue with the tubra-eTherm C9+ was that only a single shared neutral conductor was routed to the cable outlet.” Edwin Jersak solved this himself by separating the shared neutral conductor so that each heating element has its own neutral line. “The SOL•THOR supplies DC — pulsed direct current — so the neutral conductors of the two SOL•THOR units must not be combined,” he explains. He received confirmation of this solution directly from Tuxhorn at the ISH trade fair in Frankfurt.
In addition to the system controller (SystaComfort II), the homeowner operates a Raspberry Pi 4 running Home Assistant, which he set up himself. “This gives me a complete overview of the system. Everything is visualized and logged. Integration of the two SOL•THOR units, the SystaComfort II, and other devices is simple and straightforward. Access is possible from anywhere via VPN,” he summarizes.
For those who find this too complex, the my-PV Cloud offers an out-of-the-box solution for detailed monitoring of yield data, heat generation, and grid consumption. The my-PV Cloud is also available as a smartphone app.
How high is the hot water demand?
Two people live in the 160 m² single-family home, with a typical hot water consumption of around 50 liters per person per day. For the total daily hot water demand of 100 liters and space heating during the heating season, approximately 6,500 kWh of gas were previously required before installing the two SOL•THOR units.
Gas consumption reduced to one third!
The savings can currently only be extrapolated. “From the heating start on November 17, 2025 until the gas meter reading on January 9, 2026, I consumed 113 m³ of gas. Converted, that’s 1,130 kWh for 54 days of operation — around 21 kWh per day. If I calculate the heating period from November 17, 2025 to March 15, 2026, that’s 119 days. At 21 kWh per day, this results in a total gas consumption of 2,499 kWh. Previously, the annual gas consumption (excluding heating, only hot water) was about 2,829 kWh, and space heating required around 3,671 kWh. In total, this represents a gas saving of nearly two thirds — meaning only 38.5% of the original gas consumption is now required!” the homeowner calculates enthusiastically.
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What happens when there is no sunshine?
If desired, the SOL•THOR can optionally use grid electricity for backup heating when solar energy is unavailable or insufficient. This can also be done via my-PV DTO (Dynamic Tariff Optimizer) using a dynamic electricity tariff, which the customer must have independently. Via a feature in the my-PV Cloud, heat generation would then automatically be carried out during the cheapest hours.
However, Edwin Jersak does not use this feature: “No, we don’t use automated backup heating via grid electricity (also known as domestic hot water backup). With the two SOL•THOR units, we have autonomous power generation.” The system with the two devices from the Austrian PV-to-heat manufacturer my-PV has been in operation since July 2025, and the gas boiler has been switched off accordingly. “Until mid-November 2025, there was sufficient hot water. We were able to cover our domestic hot water production with solar energy well into late autumn! During the transitional season, we heat with a wood-burning stove. We’re curious to see when the sun won’t be sufficient and we’ll need to switch on the gas boiler. Two to three days of rain can easily be bridged thanks to the large 800-liter buffer storage tank,” the homeowner reports enthusiastically.
From mid-November onward, the gas boiler was activated. However, as soon as the sun is shining, the gas boiler remains off. On fully sunny days, the output of the two SOL•THOR units is completely sufficient for both hot water and space heating. “We have very good insulation, almost passive-house level — unfortunately, we’ll only be able to assess precise results in spring,” the homeowner concludes.
What are the advantages from your perspective?
“Our hot water can be produced almost exclusively with photovoltaic energy from early spring to late autumn. The gas boiler remains switched off. I also expect good support from photovoltaics during the heating season,” says Edwin Jersak.
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SOL•THOR
in use
The DC Power Manager converts solar power directly into heat – efficiently and with minimal loss by using direct current from PV modules to power a heating element.
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