PVT panels cost more per square metre than a plain PV module (roughly 1.5–2.5 times the module price), add a small glycol circuit with pump, vessel and periodic checks, deliver their heat at 10–40 °C and weigh up to about 40 kg per panel. Each of these has a standard engineering answer — a heat pump, pool or pre-heat cylinder to use the low-grade heat, a correctly commissioned hydraulic circuit and an installer who knows both trades — and in return one roof delivers electricity and heat together, with the cells running cooler and producing more power.
What is the honest list of PVT drawbacks?
Six, each with a known engineering answer:
- Capital cost per square metre. A PVT panel costs roughly 1.5–2.5 times a comparable PV module. The fair comparison is cost per kWh of total delivered energy: when the heat is used, a PVT panel delivers 3–4 times the energy of a PV module from the same area, and as a certified solar thermal collector it can qualify for heating grants that plain PV cannot.
- Hydraulic complexity on the roof. Every panel becomes a plumbing joint. Pump station, expansion vessel, air separator, glycol and a controller all appear where a PV array needed only cable.
- Low-grade heat. Uncovered panels work in the 10–40 °C band, so the design must give that heat somewhere to go — a heat pump source circuit, a pool or the lower coil of a pre-heat cylinder. Those are exactly the loads where PVT performs best.
- Maintenance the PV trade does not do. Glycol condition, system pressure and vessel charge need periodic checks, exactly as on a solar thermal maintenance schedule.
- Weight and structure. Up to about 40 kg per panel (Solimpeks' 2.7 m² PV-T 590 weighs 40 kg) against 18–23 kg for a standard PV module, plus fluid. Old timber roofs sometimes need checking.
- A thin supply chain of competent specifiers. PVT sits between the PV and the heating trades, and the design errors come from that gap.
Are PVT panels worth the extra cost?
Yes, wherever the heat has somewhere to go or roof area is limited — homes with a heat pump or a hot water cylinder to pre-heat, and hotels, gyms and pools with year-round demand. The decision hinges on two site facts rather than on any property of the panel:
| Situation | Better choice | Reason |
|---|---|---|
| Large unshaded roof, modest hot water demand | PV plus a small thermal or PVT field sized to the hot water load | Each technology sized to its own load |
| Small roof, heat pump planned | PVT | Two outputs per m², raises source temperature |
| No garden, no drilling permit | PVT | Replaces a ground loop without excavation |
| Year-round hot water load (hotel, gym, pool) | PVT or thermal | Summer heat is actually consumed |
| Holiday home, low occupancy | PV, adding PVT only if a pool or heat pump uses the heat | Heat only pays when it is consumed |
The pattern is consistent: PVT pays best where roof area is limited or a steady heat load exists, and it pays most when both are true. The full comparison is set out in PVT vs separate PV and solar thermal.
What can go wrong technically?
The failure modes are the ones a heating engineer would predict, not electrical ones. Air trapped in the array is the most common commissioning fault and it stops circulation in the affected branch silently — output simply disappears. Loss of system pressure over months, usually through a tired vessel charge or a weeping joint, does the same thing more slowly. Both are avoidable with a proper air separator, a correctly charged vessel and a pressure gauge someone actually reads.
One risk is genuinely smaller than with conventional collectors. An uncovered PVT panel stagnates below about 75 °C, against 150–200 °C for a glazed flat plate collector. Propylene glycol degrades rapidly above roughly 130 °C, so a PVT loop's fluid ages far more slowly and the overheating problems that dominate solar thermal service calls largely do not arise.
Do PVT panels reduce electricity output?
Not in normal operation — the reverse. Cell power falls by 0.25–0.34% for every degree above 25 °C, so cooling the module raises electrical yield in warm weather, typically by a few per cent annually and more in hot climates.
The exception is the insulated or glazed variant. Building a panel to reach 50–70 °C means letting the cells run hot, which costs roughly 5–8% of annual electrical yield. Choosing that variant is a deliberate trade, not a defect, and it is only correct when the load genuinely needs the higher temperature.
Which disadvantage should actually change your decision?
The absence of a heat load. Everything else on the list is a cost or an engineering task with a known solution; a house with no heat pump, no cylinder and only a combi boiler gives PVT heat nowhere to go, so the first step there is a solar-ready cylinder or a heat pump, both of which Solimpeks supplies alongside the panels. Confirm the load first, then the roof area, then the budget.
As a manufacturer of both PVT and conventional collectors, Solimpeks designs to the site: where 55–60 °C hot water straight from the roof is the main goal, a Wunder thermal array is the natural choice. What PVT does uniquely well is deliver two energy streams from one roof and feed a heat pump without an outdoor unit — and wherever those matter, the limitations above are design tasks rather than reasons to say no.
Frequently asked questions
Do PVT panels leak?
They are pressure-tested assemblies with the same joint count as a solar thermal array, so leaks come from field connections rather than from the panel. A pressure gauge and an annual check catch a slow loss long before it reaches the roof covering.
Are PVT panels harder to install than PV?
Yes, because two trades are involved. The mounting and electrical work is identical to PV, but the array must then be filled, pressurised, purged of air and commissioned as a solar thermal circuit, which a PV-only installer is not equipped to do.
How long do PVT panels last?
The same 25–30 years as good PV modules, with the hydraulic components as the wear items. Pumps, vessels and glycol are consumables on a 10–15 year cycle, and the low stagnation temperature of uncovered panels is kind to all of them.
Is PVT worth it without a heat pump?
Yes, when there is a pool or a hot water cylinder to pre-heat — both are ideal 10–40 °C loads, and the cooled cells produce more electricity at the same time. Where the goal is 55–60 °C hot water straight from the roof with no heat pump, a glazed thermal collector such as the Wunder range is the better match.