Photovoltaic-thermal hybrid modules (PVT) supply electricity and heat at the same time. They enable particularly efficient use of the roof surface, as they convert not only solar energy but also energy from the ambient air. An innovative system of this kind can raise many questions – which is why we have compiled the most frequently asked questions and answers about how Sunmaxx PVT modules work, areas of application and special features here. This section is updated and supplemented on an ongoing basis. We reserve the right to make changes accordingly. All information is without guarantee.
A PVT module is a photovoltaic-thermal hybrid module. It consists of solar cells on the front side of the module (PV) and a solar thermal heat exchanger (T) on the back. PVT modules therefore supply electricity and heat at the same time. The front side of a PVT module is no different from conventional photovoltaics. The special technological features take place on the back. The heat exchanger located here is designed in such a way that it harnesses ambient heat and heat from solar radiation.
PVT modules combine energy generation from the sun and ambient temperature in just one module. The PV cells on the front generate electricity from solar radiation, which heats up the surface of the module. This heat is absorbed by the heat exchanger on the back and transferred to a heat transfer fluid (brine). In addition to solar heat, the heat exchanger generates energy from the ambient air. This is so-called low-temperature heat, which serves as a direct heat source for the brine heat pump. PVT systems therefore not only work highly efficiently during the day in summer, but also at night and in winter. This means that detached houses can be heated all year round without a supporting heat generator. For larger projects, e.g. municipal heating networks or industrial plants with process heat, a combination of PVT and geothermal systems is often worthwhile.
PVT modules achieve an efficiency of more than 80 percent. They are four times more efficient than conventional PV modules, as they not only generate electricity from solar energy, but also heat. PVT modules also draw additional energy from the ambient air. This means that they work very efficiently, even at night – and of course on days when there is no sunshine. Further advantages of (Sunmaxx) PVT modules are:
• Electricity and heat from just 1 module
• Energy supply around the clock, at any time of year
• Maximum efficiency of the (roof) area used
• 5 to 10 % higher electricity yield due to cooling of the PV cells
• No moving parts, low maintenance
• Suitable for any roof, even in densely built-up areas
• Silent operation of the PVT modules
• Combined use with brine heat pump: no outdoor unit required, no noise emissions
• Use of excess heat for the regeneration of geothermal systems
• High price attractiveness of Sunmaxx modules due to mass production
• Significant reduction in electricity and heating costs to less than 10 cents per kWh
• Long service life of module and solar cells: 10-year product guarantee, 25-year guarantee on eletrical output
Besides the common certifications for the electrical side, we have the solar keymark. It is the most important certification for thermal collectors, especially for the granting of subsidies. Our PVT module PX-1 is of course certified according to all standards for PV and solar thermal energy. You can access the Solar Keymark certificate in our download area.
PVT is suitable for any type of building, even in older buildings with wall radiators. These do not have to be replaced by underfloor heating: Modern heat pumps can easily achieve the heating output and flow temperatures required for old buildings. For buildings from the 50s and 60s, however, we recommend considering one or two modernization measures as part of the PVT installation. For example, the heat pump can be made smaller by optimizing the thermal insulation. This automatically means that fewer PVT modules are required – so modernization would also have an economic benefit. Of course, this applies not only to single-family homes, but to all types of buildings – from apartment buildings and industrial plants with process heat to municipal heat supplies. This would require correspondingly smaller geothermal probe fields or fewer meters of depth for probe drilling. Since geothermal energy is one of the biggest cost factors in energy-efficient renovations, PVT offers a great deal of potential for money savings.
For PVT, similar guidelines apply as for conventional PV. These include sun exposure, orientation and the angle of inclination. This means that local conditions have an influence on the electricity yield. However, this is different for PVT heat yield. In contrast to solar thermal collectors, the location of PVT modules has only a marginal effect on the heat yield. Hybrid modules can be installed in all sky orientations and with inclination angles from 0° to 90°. Depending on the specific application and local conditions, the orientation of the PVT modules as well as their inclination angle may differ from a design with the highest possible electricity yield.
Various studies and research projects have been carried out over the past decades. Most of them came to the conclusion that PVT modules offer a wide range of technically suitable applications. Until now, however, system complexity and manufacturing costs have prevented the widespread use of PVT systems. Thanks to the Sunmaxx solution, costs are now finally in a range that makes PVT attractive for private and large-scale projects. As a result, more field data is available, which we naturally use for the further development and optimization of our modules. We currently have a technological lead of several years compared to our competitors, which we want to maintain and expand.
Since 2022, numerous projects have been and are being implemented with Sunmaxx, including many single-family homes and some large-scale PVT systems. The latter include the Vienna Sports Arena with over 1,130 Sunmaxx PVT modules – making it the largest PVT system in Europe. In the first half of 2025, Sunmaxx will also implement the largest PVT project in Germany with the decarbonization of the MAHLE plant in Vaihingen-Enz. More than 1,000 hybrid modules are being used here. Many systems are being monitored by our network and us. We are constantly exchanging plant data with our specialist planners and cooperation partners in order to ensure and optimize their functionality.
Sunmaxx modules do not have an insulating layer or thermal insulation on the back. On the front, they are fitted with a standard safety glass, similar to any normal PV module. An aluminum heat exchanger is attached to the back.
Yes, that is possible. However, you will need the approval of the grid operator and a specialist company to connect the system to the grid – completely identical to all conventional PV systems.
PVT can be used almost always and anywhere. The precondition is that there has to be a heat demand that meets the number of modules. For this reason, hybrid modules are usually operated in combination with brine heat pumps. They serve as an indirect heat source on the primary side of the heat pump. In special applications, such as swimming pool heating, PVT can also be used very efficiently and economically as a direct heat source. As a basic rule, PVT is always a great choice where there is heat required.
You can check out a selection of our PVT projects on the References page. Unfortunately, it is not possible to visit the PVT systems of our private and commercial customers. However, we are also implementing municipal projects: A larger PVT system with 156 Sunmaxx hybrid modules was installed on the Zehntscheuer in Leinfelden-Echterdingen in 2024. As part of the public space, this system can be viewed on site. We will keep you up to date on further municipal PVT projects with our modules.
PVT is a silent heat source on the roof. Sunmaxx hybrid modules run silently; there are no problems with noise emissions as it is the case with air-to-water heat pumps. On the contrary: PVT supplies energy for brine heat pumps, which do not require an outdoor unit and are currently installed inside the building, usually in the basement or the utility room. The noise caused by a brine heat pump is insignificant and can be ignored when planning the system.
Sunmaxx PVT modules are extremely durable. The heat exchanger on the back of the module removes the excess heat from the PV surface and dissipates it. This allows the solar cells to operate in their optimum power range, to generate a 5 to 10 percent higher electricity yield than with conventional PV modules and to prevent premature wear. All in all, we assume that our PVT modules can easily be operated for 30 years and longer – just like any common PV module.
The innovative heat exchanger technology from Sunmaxx is designed for a long service life and maximum sustainability. We offer a 10-year product warranty on our modules and a 25-year warranty on the performance of the solar cells.
Sunmaxx is a German company based in Ottendorf-Okrilla near Dresden. This is where our factory is located and where we produce our PVT modules. As a pioneer in sustainability, we attach great importance to good working conditions and European quality standards. We try to reproduce, maintain and promote the production steps that can be carried out in Europe. This is why our main suppliers come from EU countries. One exception applies to solar cells: Currently, these cannot be sourced from Europe, which is why we are dependent on imports from China. However, together with our partner Oxford PV, we are already working on a new generation of PVT modules with perovskite cells. These cells will be manufactured in Germany.
For the back of our PVT modules, we use a technology that originates from the automotive industry’s battery management system, which we have adapted to the requirements of the PV sector. Our PVT modules consist of a full-surface aluminum heat exchanger with a channel system running through it that is filled with a water-glycol mixture (brine). This technology is unique world-wide and has several advantages: It comes from mass production, is quickly available, is inexpensive to procure and can be further processed in highly automated processes. This is why Sunmaxx PVT modules are the most powerful and cost-effective PVT modules on the market.
The manufacturing process and the materials we use for our PVT modules are mostly the same as in the PV industry. The PV laminate is transferred to the usual recycling system for PV. The heat exchanger on the back of the module, on the other hand, is made of 100 percent aluminum. It can be separated from the PV side using suitable processes and be fed into the recycling flow. We are already working with established partners to recycle our modules.
As we have many project requests, it is recommended to contact us with orders about 3 to 6 months in advance.
The latest version of our data sheets is always available on our website. Please visit our download section.
There are already numerous fields of application for PVT and more will be added in the near future. In general, any load-bearing roof is suitable for the installation of our PVT modules – from single family homes to industrial buildings, from pitched roofs to flat roofs with a 0° angle of inclination. Ground-mounted PVT systems are also possible. In addition, some of our installation partners have already implemented PVT façade systems. If there is already an existing PV system that has reached the end of its service life, it can easily be replaced with PVT. The mounting system is compatible with our modules and can easily be reused; only the pipes for the heat transfer fluid need to be added. Common fields of application for Sunmaxx PVT modules are:
• Monovalent operation: PVT as sole heat source for brine heat pumps (mainly for single-family homes)
• Bivalent operation: PVT as a combined heat source together with geothermal energy or an ice storage (especially for cold local heating networks and industrial projects with process heat)
• Heat source in densely built-up (urban) areas where air-to-water heat pumps are not permitted (keyword: noise emissions)
• Alternative heat source to geothermal energy (e.g. in water protection areas where drilling and ground collectors are not permitted)
• Regeneration of geothermal systems with surplus heat from the summer months
• Decrease of geothermal costs: massive reduction of ground collector areas and depth meters for ground probes of up to 75 %
Ambient temperature is one of the most important factors in determining the possible heating power generated. To simplify one can say that, in climate conditions like in central Europe, our PVT modules can be used for the desired application. Night-time operation for radiant cooling is also possible – because the night sky offers the possibility of cooling the brine down to far below the ambient temperature.
There are and have been various technological approaches to PVT for around 50 years. Until now, however, systems had been remaining a niche; PVT projects were only possible on a small scale due to the complex and cost-intensive manufacturing processes. The novelty about Sunmaxx is that, for the first time, a PVT manufacturer has partnered with an established player in the industry, in our case an automotive supplier, and developed a holistic collector system. The components we use at Sunmaxx come from mass production, are available in large quantities and are correspondingly cost-effective for us to purchase. In combination with the automation of our PVT production, we can offer our modules significantly more cost-effectively than any other PVT manufacturer on the market. The overall performance, the wide range of possible applications and the unbeatable price-performance ratio make Sunmaxx the benchmark when it comes to hybrid modules.
Our users have been very satisfied with the Sunmaxx system so far, especially in winter operation. This applies to both monovalent and bivalent systems. We have not received any negative feedback in surveys so far. On the contrary: installation companies praise our PVT technology for its easy installation and the leak tightness of the systems. Of course, we are not resting on our laurels: We are constantly developing and optimizing the front side, i.e. the PV side, as well as the rear heat exchanger side and the peripherals. We definitely want to maintain and further extend our technological lead over our competitors.
If you already have a brine heat pump and a roof suitable for PV, you can simply install our hybrid modules instead of common PV modules. The advantage is that the system not only supplies electricity, but also provides additional source heat: this increases the efficiency of the brine heat pump. The necessary installation steps can be carried out without any concerns by a Sunmaxx partner. Depending on the project, it is important to check the local conditions and the existing brine heat pump in order to ensure an optimum design. Our partners will be happy to advise you.