PVT Hybrid Panel FAQ

Yes. A PVT (photovoltaic-thermal) hybrid panel bonds a solar thermal absorber to the back of a normal PV laminate, so one panel sends electricity to the inverter and heat to a tank or heat pump. They are an established, certified product class rather than a prototype: the thermal side is tested to EN ISO 9806 and the electrical side to IEC 61215 and IEC 61730. Solimpeks has designed and manufactured its own PV-T hybrid panels since 2008.

Sunlight strikes the PV cells, roughly a fifth becomes electricity and most of the rest becomes heat. A fluid circuit — water and glycol in copper or aluminium channels bonded to the rear of the laminate — carries that heat away to a store or a heat pump, and the cells run cooler as a result. Because crystalline silicon loses output as it heats up, the same panel gains a little on both counts. The mechanism is set out under [PVT hybrid collector](knowledge/glossary/pvt-hybrid-collector).

Per square metre of roof, clearly yes; per euro spent on electricity alone, no. A PVT panel produces electricity in the same range as an equivalent PV module and adds usable heat on top, but it costs more, needs a hydraulic circuit, and only pays back if there is a real heat demand to absorb the output. PVT wins where roof area is the scarce resource and heat is needed all year.

In central European conditions a PVT panel typically adds 200–350 kWh of usable heat per m² per year to the 160–220 kWh of electricity per m² that a PV module of the same area would produce — roughly double to triple the total usable energy from the same roof. Treat headline claims of five or six times more energy with caution: they count low-temperature heat against electricity kilowatt-hour for kilowatt-hour, which is not an equal comparison.

As an instantaneous combined figure, yes — with a cool circuit an uncovered PVT panel can convert 70–80% of the irradiance falling on it into electricity plus low-grade heat at that moment. It is not comparable with a PV module's roughly 20% efficiency, because most of that 80% is heat at 20–40 °C rather than electricity. Annual system yields are always well below the peak instantaneous figure.

Three hold up in practice: more total energy per square metre of roof, cooler cells and therefore a modest electrical gain, and — when used as a heat pump source — a heat supply that needs no borehole, no outdoor fan unit and no separate collector field. One mounting system and one set of roof penetrations serve both outputs, which simplifies the installation.

Three points to plan for: a higher price per panel than PV, offset by getting heat and power from the same roof area; a hydraulic circuit with the maintenance any solar loop implies — glycol checks, expansion vessel, pump, controller; and the need for a genuine heat demand, because unused heat is never harvested — which is why PVT is specified for buildings with year-round hot water or as a heat pump source. Asking the panel for high-temperature hot water makes the cells run hotter, so PVT systems are designed around low circuit temperatures.

Yes, where roof space is limited and heat demand runs all year — and especially when a heat pump uses the panels as its source, replacing the outdoor fan unit or a borehole. On a large roof with modest hot water demand, separate PV and solar thermal collectors can deliver the same energy for less money, so roof area and load decide. The trade-off is worked through in [PVT vs separate PV and solar thermal](knowledge/questions/pvt-vs-separate-pv-and-solar-thermal).

It depends on the panel type, not on the sun alone. An uncovered (WISC) panel is a low-temperature device that works best when the fluid entering it is at or below ambient temperature, and in practice delivers useful heat in a roughly 0–40 °C band — precisely what a heat pump evaporator, a pool or a pre-heat tank wants. A glazed PVT panel behaves like a flat-plate collector and can lift a store to 60 °C and above, at the cost of hotter cells and lower electrical yield.

Much lower than a conventional collector's if the panel is uncovered: with no glazing and no front insulation, its maximum no-flow temperature stays below roughly 100 °C, which is why aluminium and polymer components are acceptable in these panels. A glazed PVT panel is a different case — front and rear insulation can push it past 150 °C, so materials, fluid and [expansion vessel](knowledge/glossary/expansion-vessel) must all be specified for that. Compare with the 170–200 °C a glazed flat-plate collector reaches at [stagnation](knowledge/glossary/stagnation-temperature).

It is set by the antifreeze rather than the panel. Uncovered PVT panels used as a heat pump source routinely run below 0 °C by design, and a propylene glycol mixture of around 40% by volume protects to roughly −20 °C. Check the manufacturer's declared minimum operating temperature and match the [propylene glycol](knowledge/glossary/propylene-glycol) concentration to the coldest design night at your site.

The PV side works whenever there is daylight, and the thermal side keeps working in a way an ordinary collector cannot. Because an uncovered PVT panel exchanges heat with the surrounding air as well as with the sun, it can still lift a heat pump's source loop on a dull winter day and even after sunset, whenever the air is warmer than the loop. Direct hot water production does collapse in winter, which is why cold-climate PVT systems are designed around a heat pump rather than around direct hot water.

Yes — an uncovered PVT array can replace the borehole of a ground-source system or the outdoor fan unit of an air-source one, feeding a brine-to-water heat pump. The array must then be sized against the heat pump's evaporator demand rather than against hot water demand, and most designs add source-side volume so the loop rides through cloudy spells. The architecture is described in [how a PVT panel feeds a heat pump](knowledge/questions/how-does-a-pvt-panel-feed-a-heat-pump).

As a planning figure, roughly 2–3 m² of uncovered PVT per kW of heat pump heating capacity — then confirm it with a system simulation. The real number depends on the local climate, the panel's certified performance coefficients and whether the array must cover the whole evaporator load or works alongside a second source. A solar heat pump source should never be sized from a rule of thumb alone.

Yes, and it is normal. When the circuit runs below the dew point the panel collects condensation, and below 0 °C that becomes frost — which adds latent heat to the source loop as it forms. It usually clears passively with sunshine or rising air temperature, and some controllers run a short active [defrost](knowledge/glossary/defrost-cycle) using warm fluid from the store; unlike an air-source unit there is no fan and no noise involved.

Match the panel to the temperature its circuit will run at. A non-insulated or finned uncovered panel exchanges heat freely with the air, which is exactly what you want for a heat pump source loop running near or below ambient, because it can then harvest ambient heat when the sun is weak. An insulated or glazed panel keeps heat in and is the right choice only when the circuit must run well above ambient, such as direct hot water.

Front glass, encapsulant and crystalline cells as in any PV module; behind them a heat exchanger of copper or aluminium channels — often a full-surface roll-bond sheet — bonded to the laminate; rear insulation in glazed types; a frame; and hydraulic connections at each end. The electrical side terminates in a junction box with standard PV connectors, so the panel wires into an ordinary string like any module.

They need antifreeze — typically a water and propylene glycol mixture of 33–45% by volume — because a roof circuit left as plain water will freeze and split the absorber. Panels used as a heat pump source are deliberately operated below 0 °C, so glycol is a design requirement rather than winter insurance. Have the concentration and the fluid's pH checked every 2–3 years.

The risk is low, and it is a tested property rather than a matter of opinion. [ISO 9806](knowledge/glossary/iso-9806) subjects collectors to an external thermal shock test — cold water sprayed onto a hot collector — and an internal thermal shock test in which cold fluid is injected into a stagnating collector, and a certified panel must survive both without damage. Uncovered PVT panels are the least exposed of all, because they never reach the temperatures a glazed collector does.

The loop loses pressure, the gauge and the expansion vessel show it, and a correctly configured controller stops the pump before the panel runs dry. The fluid is a propylene glycol mixture of low toxicity, but it should still be kept out of drains and watercourses. In practice the great majority of leaks occur at compression fittings and flexible connectors rather than in the absorber itself.

Only if the manufacturer declares it. A [drainback system](knowledge/glossary/drain-back-system) requires every part of the absorber and pipework to empty by gravity, which demands suitable internal channel geometry and a continuous fall from panel to drainback vessel. Many PVT absorbers cannot fully self-drain, so confirm it in writing rather than assuming.

Electrically, yes — the PV laminate generates whether or not fluid moves behind it. But an unused thermal circuit still has to be left in a defined state, filled and pressurised or fully drained, according to the manufacturer's instructions. PVT earns its value when both outputs are used, so it is specified for buildings with a heat demand or a heat pump to feed.

Gross area is the overall outside dimension of the panel, while [aperture area](knowledge/glossary/aperture-area) is the smaller area through which radiation actually reaches the absorber. Certified performance data is always published against a stated reference area, so two quotes can look very different simply because one lists gross square metres and the other aperture. Compare annual output in kWh rather than area, and check which reference the figures use.

WISC stands for wind and infrared sensitive collector — the test-standard term for a collector with no front cover, whose output depends on wind speed and long-wave radiation as well as on sunshine. EN ISO 9806 tests such collectors under defined wind conditions and publishes extra coefficients for them, which is why an unglazed datasheet carries more parameters than a glazed one. Most PVT panels sold for heat pump duty are WISC, and the [Solar Keymark](knowledge/glossary/solar-keymark) certificate states it explicitly.

Plan for 25 years, the same design life as the PV module it is built from. Both certification regimes include ageing: IEC 61215 applies damp-heat, humidity-freeze and thermal-cycling tests to the laminate, and EN ISO 9806 adds exposure, stagnation and thermal-shock tests to the thermal side. Maintenance is the ordinary solar loop calendar — glycol every 2–3 years plus a visual check after severe hail — as covered under [how long solar collectors last](knowledge/questions/how-long-do-solar-collectors-last).

Judge them by certificates rather than by price. Ask for the EN ISO 9806 thermal parameters behind a Solar Keymark certificate together with the IEC 61215 and IEC 61730 electrical data; a supplier who cannot produce both is selling a panel that cannot be compared and, in several countries, cannot be subsidised. Two visually identical panels can differ by double-digit percentages in annual yield.

Any indirect tank whose coil is sized for a low-temperature heat source, or a buffer serving the heat pump. Because uncovered PVT delivers heat at modest temperature, the heat exchanger surface area matters more than the volume — the same reason heat pump cylinders use far larger coils than boiler cylinders. In PVT-plus-heat-pump systems the panels usually feed the heat pump's source side, and the tank is then specified for the heat pump, as set out in the [thermal storage tanks guide](knowledge/guides/thermal-storage-tanks-complete-guide).

Yes. In the EU, PV modules and inverters fall under the WEEE Directive (2012/19/EU), so producers must finance take-back and recycling, and the glass, aluminium frame and copper or aluminium absorber of a PVT panel all go into conventional recycling streams. Ask a supplier which national WEEE compliance scheme they are registered with — it is a fair question at tender stage.

Solar circuits use propylene glycol rather than the toxic ethylene glycol, because it is readily biodegradable and of low toxicity — the same reason it is accepted in food and pharmaceutical use. A domestic circuit holds only a few tens of litres, and drained fluid belongs at a chemical or waste-oil collection point, never in a drain. Inhibitor packages differ between products, so dispose of the fluid as the manufacturer's safety data sheet directs.