AHU Cost for a Factory or Pharma Plant: Specification, Filtration and Cost Drivers

An air handling unit's cost follows airflow first, then the static pressure the fan must overcome, the filter train, the coil duty and the casing build. A factory-office AHU and one feeding a classified pharma room can differ widely at the same airflow because of filtration, controls, materials and validation papers. We quote no price here; this guide shows what to specify so that quotes can be compared fairly.

What sets the cost of an AHU?

What changes between a factory AHU and a pharma AHU?

Most of the difference is not the box. It is the rules for the room the air goes into. India's revised Schedule M (G.S.R. 922(E), 28 December 2023) requires the HVAC systems of a manufacturing plant to be designed, installed, qualified and maintained, and it sets four clean-area grades, A to D, for sterile products. In its sterile-products part it gives guidance values you should read before specifying: adjacent rooms of different grades should differ by approximately 10 to 15 Pascal in pressure, and a warning system should indicate failure of air supply, with pressure differentials recorded and failure alarmed. It leaves the number of air changes to be appropriate for the size of the room, equipment and personnel, and does not fix a figure. The text is in the gazette notification.

For the filter train, the same part requires HEPA filters to be leak-tested in place at a recommended interval of six months, not exceeding twelve. This matters to cost because the AHU and the terminal housings must allow an aerosol challenge and a scan: test ports, upstream mixing and access. A non-sterile pharma plant, a food unit or an electronics assembly line will have different needs set by its product and its customers' audits. Our note on GMP cleanroom HVAC basics and the cleanroom and process cooling page go further.

Why do filters and pressure drop decide running cost?

Fan power follows a simple relation: kW is roughly airflow in m³/s times pressure in Pa, divided by 1,000 and by the overall fan efficiency. An illustrative case: 10 m³/s at 1,000 Pa and 60% overall efficiency draws about 16.7 kW. Add a HEPA stage that costs a further 250 Pa and the draw rises by about 4.2 kW, which over 8,760 running hours is about 36,500 kWh a year, before the filter gets dirty. Those are arithmetic, not a quotation for any project, but they show why a cheaper unit with a high-resistance coil or a cramped filter section can cost more over its life.

The Energy Conservation Building Code 2017 sets minimum fan efficiency requirements for supply and return fans above 0.37 kW in buildings it covers, exempts fans in health care buildings with HEPA filters, and states that it does not apply to equipment and parts of buildings that use energy for manufacturing processes (see the code). Whether it binds a given factory depends on building use and your state's adoption. Use it as a benchmark even where it does not bind.

How do you build a budget without a price list?

1. Heat load first. Run a first-pass tonnage with the AC tonnage calculator, then have a designer confirm it room by room, with process heat, people, lights, fresh air and infiltration.
2. Airflow and pressure budget. Turn the load into supply air, then list the pressure drop of each element in the path. Add margin for filter loading.
3. Fix the room class and its pressure, temperature and humidity targets. This sets filtration, controls and documentation.
4. Issue one specification sheet to every bidder, with the table above as its backbone.
5. Compare on that sheet, not on a brochure. Ask for fan efficiency, filter pressure drops, panel construction and test documents.
6. Put numbers on running cost using the relation above and a spare filter set per year.

AHU supply is one line in an HVAC package. Ductwork, chilled-water piping and plant, electrical panels, controls, testing and balancing, and validation support are the others. Ask each bidder to mark each as included or excluded.

What makes AHU quotations misleading?

• Clean-filter pressure drop. A quote that states fan power at clean filters understates the running load once the filters load up. Ask for the dirty-filter figure and the changeout pressure.
• Missing terminal HEPA housings and test ports. They are often priced elsewhere or not at all, then arrive as a variation.
• No part-load control. A unit sized for peak load that cannot turn down wastes energy and can lose humidity control in mild weather.
• Drain trap height. A condensate drain on a negative-pressure section needs a trap deeper than the fan pressure, which means plinth height. Settle it before civil work.
• Access. Coil pull-out space and filter access are part of the unit's real footprint. See the AHU room size guide.

How Secured Engineers helps

We design HVAC in-house for factories and pharma and food plants, then supply and install it with the electrical and fire scope under one contract if you want that. Our AHU, FCU and air distribution page describes what we handle. Fire NOC, CEIG and DISCOM filings are done by our own team. We work from offices in Noida (Delhi NCR) and Ludhiana, with 535+ projects across 18+ states and 89.77% repeat clients.

If you hold a quotation or a BOQ for your AHUs, send it and we will compare it against the specification points above and mark the gaps. Message us on WhatsApp, call +91 70099 85817, or ask for a free proposal.