Frequently asked questions

The IESS (Integrated Energy Saving System) Panel is a rooftop solar thermal panel that connects to your inverter AC system, such as a VRF/VRV or chiller. It uses the sun's heat to do part of the compressor's work, cutting AC electricity use by up to 40% while delivering the same or better cooling.

Yes. IESS (Integrated Energy Saving System) is Arkhe Energie's name for the Hybrid Thermal Solar (HTS) panel. The technology was developed by SunTrac, USA, and the panel is made in India by Perfect Infraengineers. A VRF system fitted with HTS panels is often called a Hybrid VRF or solar-assisted VRF.

No. The IESS Panel adds solar heat directly to the refrigerant in your AC's refrigeration cycle. Your AC then runs on a mix of electricity and solar energy, so it draws much less power from the grid.

PV panels turn sunlight into electricity, which is fairly inefficient per square foot. The IESS Panel puts concentrated solar heat straight to work inside the AC cycle. It is about 1200% more space-efficient than PV panels, which matters when roof space is limited.

No. Solar water heaters and other thermal collectors try to add as much heat as possible. That doesn't work in an AC, because uncontrolled heat would disrupt the refrigeration cycle. SunTrac spent ten years developing the control software, which decides when not to add heat. The panel adds only the energy your AC can use, and turns its reflectors away when that's enough.

The panel is manufactured in Navi Mumbai by Perfect Infraengineers Ltd. under a technology transfer agreement with SUNTRAC, USA, the international patent holder. SUNTRAC spent ten years (2008–2018) developing the technology.

Any system with an inverter (variable-speed) compressor: VRF/VRV systems, inverter ACs and chillers. It works with new installations and retrofits alike. Air-cooled chillers benefit far more than water-cooled ones.

Yes. A chiller uses the same refrigeration cycle as a VRF, and the panel works with the common refrigerants in both, including R410A (VRF) and R134a (chillers). Air-cooled chillers benefit the most. Water-cooled chillers see smaller savings.

The panel doesn't depend on the brand, only on the refrigeration cycle. It has been tested with 12 AC brands: LG, Daikin, Carrier, Toshiba, Hitachi, Mitsubishi Heavy, Mitsubishi Electric, Samsung, Voltas, Blue Star, Midea and Reynold.

Three simple things:

• An inverter AC (VRF/VRV or chiller)
• Mainly daytime AC usage
• The outdoor unit (ODU) close to the terrace or roof

Not sure? Book a free site assessment and we'll check for you.

No. The IESS Panel has its own controller and makes no changes to your AC manufacturer's control system. The AC's own logic keeps setting the compressor speed based on cooling demand. Because the sun supplies part of the energy, the compressor simply needs to work less.

Hot refrigerant gas leaving the compressor passes through the rooftop panel. Sun-tracking parabolic reflectors concentrate sunlight onto the copper manifold, adding heat and pressure to the gas before it goes to the condenser. The compressor's job is to raise the gas's pressure, and the sun now does part of that, so the compressor slows down and uses up to 40% less power.

See the working diagram →

In a closed refrigerant loop, pressure and temperature are linked. The compressor uses electricity to raise the refrigerant to high pressure and temperature, and the panel adds solar heat at exactly that stage. Cooling still happens indoors at the evaporator, unchanged. The panel only takes over part of the compressor's work.

The controller keeps the reflectors out of circuit and your AC runs exactly as it normally would. You get full cooling at all times, and savings whenever the sun is available.

The controller continuously monitors the temperature of the refrigerant leaving the panel. It adds heat gradually, and turns the reflectors away from the sun if the gas gets too hot, keeping the system within safe limits.

Positively. With the sun sharing the load, the compressor runs at partial load and lower speeds for longer, which reduces wear and extends the life of the HVAC system.

A 100% aluminium enclosure (8011-H14) with a 4 mm hardened clear glass cover. Inside are copper tube absorbers (⅝″ and 1⅛″) with a selective coating (absorptivity 0.92–0.96), sun-tracking parabolic reflectors driven by stepper motors, and 9 mm EPDM insulation.

Full technical specifications →

The IESS Panel comes with a 5-year product warranty and has a design life of 15 years.

Yes. It is certified GreenPro by CII-IGBC and recognised by GRIHA, two programmes that recognise products with a reduced environmental impact.

One panel measures 8 × 4 ft (100″ × 52″ × 7″), needs around 32–40 sq ft of roof, and weighs about 86 kg. Where space is tight, it can be mounted on an MS structure above the outdoor unit, since hot air from the ODU does not affect its working.

One IESS Panel serves 10 HP (7.5 TR / 90,000 BTU) of AC capacity. For example, a 60 HP VRF system typically needs six panels. We confirm the exact number during the site assessment.

With proper planning, a panel typically takes 1–2 days to install. It needs some copper piping, four copper joints and one electrical connection.

Everything: site assessment, technical proposal, supply, installation, commissioning and ongoing support.

Up to 40% on AC electricity bills. Across 32 tested sites the average was 39.8%, with individual sites ranging from 26% to 55%. Your actual savings depend on location, season and cooling load. See site-by-site results →

At each test site, the AC's energy use is metered for a period without the panel and then with it, under comparable conditions. The results are signed off by the site's own facility or engineering team. Across 32 sites the average saving was 39.8%, and the average was above 36% in every season. See all results →

A 740 HP building running 67 panels. In total, about 1,000 panels serve roughly 10,000 TR of air conditioning at around 100 sites in India.

The typical return on investment is around 3 years, on a panel that lasts 15 years. Try our savings estimator →

Yes. The IESS Panel attracts 12% GST (compared with 18% on conventional HVAC equipment) and qualifies for accelerated depreciation, which improves your ROI further. Please confirm the details with your tax advisor.

Yes. The panel is listed on GeM, and NTPC, REC, DMRC, the Municipal Corporation of Gurugram and PWD Chhattisgarh have ordered through it. It is also specified in PWD SOR / DSR items and tenders. See the tender description →

Yes. The panel is certified GreenPro by CII-IGBC and recognised by GRIHA, so it earns points in green building assessments.