I'm Chetan Ghia, and I work alongside my family at eNarayan Elex India Pvt Ltd, a Hyderabad-based B2B electrical distributor. We're Channel Partners for Lloyd air conditioners among the 230-plus brands we distribute, and over 25 years we've supplied electrical and infrastructure products to a wide range of commercial and institutional projects across Telangana, including office campuses in Madhapur and large-format sites like Cricket Stadium in Uppal. One question that comes up constantly from facility teams and contractors is deceptively simple: how big an AC do we actually need for this space? The honest answer is that the square-footage rule of thumb most people reach for first is a starting point, not a calculation, and for a commercial space it can leave you meaningfully wrong in either direction.
A lot of the guidance floating around for air conditioner sizing is written for bedrooms and living rooms. Commercial spaces break that logic in a few specific ways. Occupancy density is usually far higher than a home, since a meeting room or open office packs more people per square foot than a living room ever will, and people are a real heat source. Equipment load is also different, a floor full of computers, servers, or commercial kitchen equipment generates heat that a residential calculation never accounts for. And operating hours are longer and more continuous in most commercial settings, which changes how much efficiency and duty-cycle tolerance actually matter over a year, not just on the hottest afternoon.
In a climate like Hyderabad's, where our own business operates and where cooling has to hold up through long, hot stretches of the year, getting this calculation wrong doesn't just mean a slightly warm room. It means either an undersized system running flat out and never quite catching up, or an oversized one that short-cycles, struggles with humidity, and burns more on the electricity bill than it should for the comfort it delivers.
I use a four-point framework with facility teams and contractors trying to size cooling properly rather than guess. I call it the LOAD Check, because that's exactly what you're trying to calculate.
L — Layout and square footage. This is where most rule-of-thumb estimates start and stop, and it's genuinely the first input you need: floor area, ceiling height, and how the space is divided. But it's the floor of the calculation, not the whole thing. A tall warehouse ceiling and a standard office ceiling at the same square footage carry very different volumes of air to cool.
O — Occupancy and equipment heat gain. How many people will typically be in the space, and what's running in it. A conference room that seats twenty generates real, sustained heat from those twenty bodies alone. A server room, a commercial kitchen, or a floor of desktop workstations adds heat load that has nothing to do with square footage and everything to do with what's plugged in and how many hours a day it runs.
A — Aspect and exposure. Which direction the space faces, how much glazing it has, and how much direct sun it gets through the day. A west-facing glass-fronted office in Hyderabad is fighting a very different afternoon heat load than an interior room with no external walls at all, even at identical floor area.
D — Duty cycle and efficiency rating. How many hours a day the system will actually run, and for how much of the year. A unit that runs eight to ten hours a day, five or six days a week, behaves very differently over its lifetime than one that runs for a few hours in the evening. This is where star rating and inverter versus non-inverter technology stop being a minor spec and start affecting the real running cost, since the same nominal capacity can carry very different electricity costs depending on how many hours it's actually working.
Myth 1: A bigger unit will always cool a space faster and better.
Oversizing causes its own problems. A unit that's too large for the space cycles on and off quickly, cools the air but doesn't run long enough to properly dehumidify it, and wears out its compressor faster from the constant starting and stopping. Right-sized and running steadily beats oversized and cycling.
Myth 2: One square-foot-per-ton ratio works across every type of commercial space.
The same floor area with different occupancy, equipment, and sun exposure needs different capacity. A quiet back office and a customer-facing floor with the same footprint are not the same cooling problem.
Myth 3: Star rating only matters if the space is occupied around the clock.
Most commercial spaces run cooling for the bulk of a working day, which for many businesses adds up to more annual hours than a typical home. Over that many running hours, the efficiency difference between rating tiers compounds into a meaningful cost difference, not a marginal one.
Myth 4: Sizing is a one-time calculation you do at fit-out and never revisit.
If a space changes use, whether that's more desks, a server rack added, or a room repurposed from storage to a meeting room, the heat load calculation changes with it. A system sized correctly for the original layout can be undersized the moment the occupancy or equipment profile shifts.
Here's a hypothetical scenario to show the LOAD Check in practice, not an account of an actual project. Imagine a facility manager fitting out a mid-sized office floor in a Hyderabad business district, similar in scale to the commercial campuses in areas like Madhapur. A rule-of-thumb calculation based purely on square footage might land on one tonnage figure. Running the LOAD Check, though, the manager would also factor in that the floor seats sixty people at peak occupancy, houses a small server room that runs continuously, and has a glass frontage facing west that catches direct afternoon sun for several hours. Each of those factors pushes the required capacity, and the placement of units, beyond what the square-footage number alone would suggest. The final sizing decision ends up meaningfully different from the first estimate, and the duty-cycle consideration also shapes which star rating makes sense given the floor will run cooling for most of a nine-to-six working day.
| What's Considered | Square-Footage Rule of Thumb | Proper Heat Load Calculation |
|---|---|---|
| Floor area and ceiling height | Yes, primary input | Yes, starting input |
| Occupancy density | Not accounted for | Factored in directly |
| Equipment and machinery heat | Not accounted for | Factored in directly |
| Sun exposure and glazing | Not accounted for | Factored in directly |
| Operating hours and duty cycle | Not accounted for | Used to inform efficiency and star-rating choice |
| Risk of under- or oversizing | Higher, especially for dense or equipment-heavy spaces | Lower, tailored to the actual space |
I'm writing this from the distributor side, so weigh it accordingly. But the reason I push facility teams toward a proper load calculation rather than a quick square-footage number is that we've supplied into enough commercial and institutional projects across Hyderabad over the years to see how differently two similarly sized spaces can actually behave once people, equipment, and sun exposure are in the picture. The square-footage rule isn't wrong, it's just incomplete, and for a commercial space running cooling most of a working day, incomplete sizing shows up on the electricity bill and in comfort complaints long after the fit-out is finished.
1. What's the biggest mistake people make when sizing AC for a commercial space?
Relying only on square footage and skipping occupancy, equipment heat, and sun exposure, all of which can shift the required capacity meaningfully even at the same floor area.
2. Does a higher star rating matter more for commercial spaces than homes?
It can, since commercial spaces frequently run cooling for more hours per day across more days of the year than a typical home, which compounds the efficiency difference over time.
3. How does equipment like servers or commercial kitchen appliances affect AC sizing?
Equipment generates heat that has nothing to do with the room's square footage. A space with a server room or commercial kitchen needs its equipment heat load added on top of the standard occupancy and floor-area calculation.
4. Should AC sizing be recalculated if a space changes use later?
Yes. A change in occupancy, added equipment, or a change in how the room is used shifts the heat load, and a system sized for the original layout can become undersized or inefficient for the new one.
5. Where should I start if I want a proper load calculation rather than a rough estimate for a commercial fit-out?
Start by documenting the space's floor area, expected peak occupancy, any heat-generating equipment, and its sun exposure, then work through those factors with a supplier or HVAC professional rather than applying a single square-foot-per-ton ratio.