PVT vs. Solar Thermal

PVT and solar thermal systems are two very different technologies. Conventional solar thermal collectors do not generate electricity. They use the sun’s energy solely for heating support and domestic hot water production.
In contrast, PVT modules generate both electricity and heat at the same time. The heat provided by PVT modules is at what is known as a low-temperature level. This heat serves as a direct energy source for a brine-to-water heat pump.
While traditional solar thermal systems are typically used as a supplement to a gas heating system, a PVT system combined with a brine-to-water heat pump operates as a fully independent and comprehensive heating solution.

Sunmaxx modules are uncovered PVT modules, meaning they do not heat up nearly as much as solar thermal collectors. The latter can reach stagnation temperatures of up to 180 °C.
In contrast, Sunmaxx PVT modules typically operate at around 30 °C when heat is being extracted. During brine stagnation (for example, in midsummer when there is little or no demand for heating or hot water), the module temperature reaches a maximum of about 81 °C – similar to standard PV modules. However, even this is relatively rare.
Plus, our modules and associated piping are not affected by vapor formation or overpressure. The circulating brine is therefore not at risk of decomposing: something that can occur more frequently in traditional solar thermal systems.

No, Sunmaxx PVT modules do not experience any problems with overpressure. Even during stagnation (when the brine circuit is idle), the module temperature does not exceed 81 °C. As a result, there is no risk of overpressure or decomposition of the heat transfer fluid. Leaks are also virtually eliminated when the system is installed correctly.

PVT technology cannot be directly compared with conventional solar thermal systems. Traditional vacuum tube collectors (or flat plate collectors) are covered or insulated to prevent the heat generated at the surface from radiating back into the environment or being lost to the surrounding air.

PVT modules, on the other hand, are uncovered and uninsulated collectors that deliver what is known as low-temperature heat. As the name suggests, the temperature differences between the module, heat transfer medium, and ambient air are minimal, which means heat losses are negligible and insulation is unnecessary. This low-temperature heat serves as an energy source for a brine-to-water heat pump. During the compression process, the heat pump raises this temperature to the level required for space heating and domestic hot water production. In many cases, PVT acts as the sole heat source for the heat pump, forming a complete heating system for buildings.

In contrast, conventional solar thermal systems are typically used to support gas or oil heating. Because they operate with high supply temperatures of 50 to 60 °C, solar thermal systems are generally unsuitable for use with heat pumps.

PVT is not classified as a solar thermal system, even though it also generates heat from solar radiation. Instead, the technology provides low-temperature heat, which serves as a direct – and often sole – heat source for brine-to-water heat pumps.
From a funding and subsidy perspective, PVT is therefore considered a complementary measure to the heat pump rather than a standalone solar thermal system.

Currently, solar thermal is only worthwhile in niche applications. These include, for example, large-scale systems with a constant (high) heat demand or hybrid networks. The reason: solar thermal uses the sun’s energy exclusively to generate heat in the high-temperature range. This only works effectively when a stable heat demand exists. PVT is the better solution both technically and economically because:

1. PVT combines photovoltaics (electricity) and solar thermal (heat) in a single module. The modules therefore generate both electrical energy and low-temperature heat simultaneously – ideal for brine-to-water heat pumps. A PVT system together with a brine-to-water heat pump forms a self-sufficient, fully functional heating system, whereas solar thermal is usually only used as a supplementary system, for example in combination with oil or gas boilers or pellet stoves.
2. Solar thermal involves relatively high investment costs per kilowatt-hour of usable heat. Moreover, it mainly produces heat when it is least needed – in the summer. PVT, on the other hand, combines two energy revenue streams (PV and thermal) in one system. The heat serves as the source for the brine-to-water heat pump, while the electricity can be used directly in the building or fed into the grid. This increases the efficiency of the heat pump and reduces electricity costs. As a result, the investment cost per kilowatt-hour of usable energy is significantly lower with PVT.
3. PVT makes double use of roof space. This is highly beneficial from both an ecological and economic perspective. A great side effect: the heat extraction cools the PV side of the module, resulting in an annual electricity yield that is 5 to 10% higher than with conventional PV systems. PVT therefore not only operates more efficiently than a PV system of the same size but also provides heat and achieves a total efficiency of over 80 percent.
4. PVT integrates more effectively into electrical and digital energy systems than solar thermal systems.

Conclusion: While technically sound, solar thermal is economically and systemically outdated in many applications. The direction of the energy transition is clear: electricity is becoming the central energy carrier, and heat pumps are becoming the standard solution for heating and hot water. This requires systems that intelligently combine electricity and heat – exactly what PVT does. PVT is the next logical step because it makes the most efficient use of available roof space.

Hybrid modules deliver both source heat and electricity for brine-to-water heat pumps, reduce CO₂ emissions, and are more cost-effective in the long run. Where solar thermal was once considered a “green heat supplier,” PVT is now the heart of modern energy systems. And the best part: PVT is not a compromise but an evolution – a technology that proves efficiency and economic viability are not mutually exclusive.