Why India's AHUs Need an Upgrade: The Business Case for EC Fans

Key points. AHU fans are among the longest-running loads in an Indian commercial building, and most still run belt-driven at fixed speed. For a portfolio of 40 AHUs running 24x7, fans alone cost about ₹2.1 crore a year at ₹10 per unit. Replacing just the fan section with EC fans and adding speed control typically saves 30–50% of that, without replacing the AHU, and pays back quickly. Energy savings are only part of the case: upgrades also improve uptime, maintenance, air quality and ESG reporting.

India's commercial building stock grew fast on a simple rule: buy the AHU with the lowest first cost. That usually meant a forward-curved blower driven by belts from an induction motor, set to one speed at commissioning. Many of those AHUs are still running, with motors and belts replaced as they fail. They keep the building cool, and they waste a large share of the electricity they use. Here is why that is now worth fixing.

Five reasons to upgrade now

1. Electricity is expensive and AHU fans never stop. At around ₹10 per unit, a single 6 kW AHU fan running 24x7 costs about ₹5.3 lakh a year. IT parks, hospitals, pharma plants and data centers run dozens of them around the clock.

2. Cooling demand is rising fast. The IEA estimates that cooling already accounts for slightly more than 10% of India's electricity demand and will more than double by 2035. The India Cooling Action Plan sets a national goal of cutting cooling energy needs by 25–40% by 2037-38. Buildings that cut their own HVAC energy now get ahead of tighter codes and tariffs later.

3. The building code is getting stricter. ECBC 2017 sets minimum fan efficiencies of 60–70% and motor classes of IE2 to IE4, depending on tier. Its successor, the 2024 Energy Conservation and Sustainable Building Code, raises the bar for new buildings as states adopt it. Older belt-driven forward-curved fans can struggle to meet the higher tiers. We explain the rules in IE2 to IE5 and ECBC.

4. ESG disclosure needs real numbers. SEBI requires India's top 1,000 listed companies to report energy use and emissions through the Business Responsibility and Sustainability Report (BRSR). Their landlords and suppliers are increasingly asked for the same data. A retrofit that cuts HVAC energy and measures it gives you numbers you can report.

5. Old fans are a reliability risk. A belt-driven AHU has one fan. When its belt snaps or its bearing fails, the whole unit stops. Belts also need regular tensioning and replacement, and they lose efficiency as they wear.

What it is worth across a portfolio

Take an IT park with 40 AHUs, each with a 6 kW belt-driven fan running 24x7:

Assumptions: 8,760 hours a year, ₹10 per unit, and the CEA grid emission factor of 0.71 tCO₂/MWh. Published EC retrofit results mostly range from 25% to 50%. In India, Capgemini replaced more than 1,000 fans across eight campuses and reported about 30% lower fan energy.

Upgrade the fan section, not the whole AHU

Replacing a whole AHU means new casings, coils, ductwork connections, cranes and long shutdowns. In most cases the casing and coils are fine; the fan section is what wastes energy. An EC fan retrofit replaces only the blower, motor, belts and pulleys with one or more direct-drive EC plug fans:

• Same casing, same coils. The new fans mount in the existing fan section.
• Short shutdowns. A typical swap fits within a planned maintenance window. Phased replacement keeps the building running.
• Built-in speed control. EC fans take a speed command directly, with no separate VFD.
• Redundancy. Larger AHUs can take two or more smaller fans in place of one blower, so a single failure no longer stops the unit.

Then let the fans respond to the building

An EC fan running at a fixed speed captures only part of the savings. The larger gain comes from matching airflow to the real load: occupancy, temperature, humidity and CO₂. Because fan power falls with the cube of speed, a fan running at 80% uses about half the power.

In many buildings the BMS holds AHU fans at a fixed speed, so the savings never materialise. GarvataAI AHU Control adds an edge controller to each AHU. It reads temperature, humidity, pressure and CO₂, tunes fan speed continuously within the limits you set, and keeps control local if the network drops. The cloud dashboard shows energy, air quality and fan health across every building.

Signs your AHUs are ready for an upgrade

• Belts are replaced or re-tensioned several times a year
• The fan runs at the same speed day and night, weekday and weekend
• A VFD is installed but sits at 50 Hz all the time
• Nobody can say how many kWh the AHU fans use each month
• AHUs are noisy, or vibration has crept up over the years
• Fan motors are more than ten years old, or are IE2 or below

If you tick three or more, an energy survey will almost certainly find a business case.

How to start

1. Survey. Measure fan input power and running hours on a sample of AHUs, and collect the AHU schedule.
2. Estimate. Multiply fan kW by running hours and your tariff to get today's cost, then apply 30–50% to size the savings across the portfolio.
3. Pilot. Retrofit a few AHUs with EC fans and control, and meter before and after.
4. Roll out in phases, worst performers first, during planned maintenance windows.

Garvata EC fans and GarvataAI AHU Control are available now. See the commercial solution or talk to us about your buildings.

Sources

1. IEA, "India's electricity demand grows at night: managing rising cooling demand" (June 2026). iea.org
2. IEA policy database, India Cooling Action Plan (2019). iea.org
3. Bureau of Energy Efficiency, Energy Conservation Building Code 2017 (mirrored by LBNL). lbl.gov
4. SEBI, "Business responsibility and sustainability reporting by listed entities" (May 2021). sebi.gov.in
5. ebm-papst, "Achieving climate targets with EC fans and an energy command center" (Capgemini India, 2025). ebmpapst.com
6. US DOE, Replace V-Belts with Notched or Synchronous Belt Drives, Motor Systems Tip Sheet #5. energy.gov
7. Central Electricity Authority, CO₂ Baseline Database v21.0 (December 2025). cea.nic.in