What Size 6–10 Ton Packaged Unit Does Your Building Actually Need? Tony’s Commercial Load Rules Explained
Sizing a commercial 6–10 ton packaged AC/gas furnace unit isn’t like picking a home air conditioner.
There’s no “one ton per X square feet” rule.
There’s no chart that magically tells you what to buy.
And there’s no salesperson alive who can size your building correctly without asking a LOT of questions.
Tony has spent decades installing, repairing, and replacing 6–10 ton rooftop and pad-mounted packaged units for restaurants, strip malls, medical offices, retail stores, warehouses, salons, gyms, and small manufacturing buildings. After seeing hundreds of bad installs oversizing and undersizing units, he knows the truth:
Commercial sizing is about heat load, not square footage.
Loads change based on:
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occupancy
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sunlight
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lighting intensity
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ceiling height
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insulation
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outside air requirements
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open doors
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equipment loads (computers, ovens, refrigerators, machinery)
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building purpose
This is Tony’s full commercial load-sizing playbook, written in the same way he trains new techs in the field.
If you’re choosing a 6–10 ton packaged system, read this before spending a dollar.
1. First Rule: Square Footage Means NOTHING Without Heat Load
Most business owners say:
“My building is 4,000 square feet. That means I need an 8-ton unit, right?”
Wrong.
Commercial square footage tells you almost nothing.
Tony installed:
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a 6-ton unit in a 6,000 sq ft storage warehouse
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a 10-ton unit in a 2,400 sq ft restaurant
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an 8.5-ton unit in a 3,500 sq ft retail store
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two 7.5-ton units in a 5,000 sq ft gym
Why?
Because heat load changes everything.
(Reference: Residential HVAC Load Calculation Standards)
2. Real Commercial Heat Load Factors Tony Uses
Commercial buildings don’t heat up the way homes do.
They have:
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more people
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more glass
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more lighting
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more equipment
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more infiltration
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more heat sources
Tony looks at all of the following:
✔ Occupancy Load
Every person generates 250–450 BTU/hr depending on activity.
Gyms and restaurants have the highest loads.
Offices and retail stores have moderate loads.
Warehouses have the lowest.
✔ Lighting Load
LED lighting = low heat
Fluorescent = moderate
Halogen & track lighting = massive heat gain
✔ Equipment Load
Computers, servers, ovens, refrigeration cases, cash-wrap electronics — these add thousands of BTUs.
✔ Solar Load
South- and west-facing glass can add the equivalent of another 2–4 tons of cooling capacity.
✔ Ventilation / Outside Air
Fresh air dampers and economizers drastically increase load requirements.
✔ Ceiling Height
Tall ceilings = more cubic feet = more cooling.
✔ Occupied Hours
A building open from 6am to midnight needs more capacity than a 9–5 office.
✔ Insulation / Envelope
Older buildings leak heat.
Newer buildings hold it.
This is why square footage alone is worthless.
(Reference: Home Insulation and Envelope Performance Manual)
3. Tony’s Real Sizing Ranges for 6–10 Ton Units
Tony doesn’t do generic “rules of thumb.”
He does ranges based on building type.
Use these to get in the right ballpark.
A. Retail Stores (2,000–6,000 sq ft)
Typical Need: 6–8 tons
Factors:
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high lighting
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moderate occupancy
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frequent door openings
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large display windows
B. Restaurants (1,500–4,000 sq ft)
Typical Need: 8–10 tons
Why?
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kitchens generate enormous heat
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long operating hours
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high humidity from cooking
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constant door traffic
Tony never sizes restaurants small. Ever.
C. Office Buildings (2,000–8,000 sq ft)
Typical Need: 6–10 tons
Depends on:
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number of people
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computer/server load
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glass exposure
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conference room usage
D. Gyms (2,000–5,000 sq ft)
Typical Need: 8–10 tons
Why?
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high activity level
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high humidity
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constant airflow demand
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huge occupancy spikes
E. Small Warehouses (5,000–10,000 sq ft)
Typical Need: 3–7 tons, but often supplemented by:
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ceiling fans
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destratification fans
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spot cooling
Warehouses rarely need a full 6–10 ton system unless office space is attached.
F. Medical Clinics / Dental Suites
Typical Need: 7–10 tons
Why?
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strict temperature control
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heavy lighting
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long occupied hours
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equipment heat load
G. Salons & Barbershops
Typical Need: 8–10 tons
Why?
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hairdryers
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styling tools
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lighting
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high humidity
H. Churches / Community Rooms
Typical Need: 6–10 tons
Occupancy swings are huge.
When the room fills, load skyrockets.
4. Gas Furnace Capacity Matters Too — Not Just Cooling
Packaged units combine AC + gas furnace in one cabinet.
Tony matches heating based on:
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winter outdoor temps
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occupancy
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building insulation
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duct size
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fresh air requirements
Typical heating outputs:
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100,000–200,000 BTU furnaces for 6–10 ton packaged units
Undersized heating = cold winter mornings
Oversized heating = temperature swings
(Reference: Regional Climate and Temperature Zone Guidelines)
5. Fresh Air Requirements Can Add 1–3 Tons to Your Load
Commercial code often requires:
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outside air intakes
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ventilation
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economizers
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makeup air
Bringing in fresh outdoor air means:
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more air to cool
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more humidity to remove
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more heating needed in winter
Tony commonly adds 10–25% more cooling capacity for buildings with heavy fresh-air requirements.
6. Internal Heat Loads — The Hidden BTU Monster
Tony always asks:
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Do you have server racks?
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Do you have refrigeration?
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Do you have ovens?
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Do you have heat-producing machinery?
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Do your lights run hot?
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Do employees work vigorously (gyms, kitchens)?
Equipment heat is often misunderstood.
Servers alone can add ½ to 2 tons of cooling load.
A refrigeration line-up in a small store can add 3–4 tons of cooling load.
This is why restaurants and retail stores often need 8–10 ton units even though they’re smaller than offices.
7. Ceiling Height Changes the Actual Load Calculation
Commercial ceilings range from 8ft to 20ft.
Tony adjusts cooling for ceiling height:
Add 10% cooling load for every 2 feet above 8 feet of height.
High ceilings trap heat above the occupied zone — and that heat eventually drops.
8. Airflow and Ductwork Determine Whether the Tonnage Even Works
A perfect 10-ton unit with bad ductwork cools like a 6-ton.
Tony always checks:
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return air size
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static pressure
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duct leaks
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plenum transitions
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airflow balancing
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velocity noise
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diffuser placement
Commercial ductwork must deliver 350–450 CFM per ton.
If airflow is wrong, tonnage doesn’t matter.
(Reference: Air Distribution and Duct Sizing Reference)
9. When You Need MULTIPLE Units Instead of One 10-Ton
Tony often splits cooling into multiple units for:
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zoning
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redundancy
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easier service
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balanced airflow
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load distribution
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future building expansions
Examples:
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Retail store → 2 x 5-ton
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Office → 1 x 7.5-ton + 1 x 5-ton
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Restaurant → 1 x 10-ton + hood makeup air
Multiple units = better comfort and reliability.
10. Oversizing Is Just as Bad as Undersizing
Oversizing causes:
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short cycling
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poor humidity control
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noisy operation
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reduced indoor comfort
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furnace cycling issues
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high utility bills
Undersizing causes:
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long run times
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failure to reach setpoint
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frozen coils
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overheated compressors
Tony sizes for peak load, but never goes crazy with tonnage.
11. Tony’s Quick Sizing Cheat Sheet
Here’s Tony’s rough ballpark cheat sheet — NOT the final answer, but a starting point:
| Business Type | Typical 6–10 Ton Range |
|---|---|
| Retail | 6–8 tons |
| Restaurants | 8–10 tons |
| Offices | 6–10 tons |
| Gyms | 8–10 tons |
| Warehouses | 3–7 tons |
| Medical | 7–10 tons |
| Salons | 8–10 tons |
| Churches / Halls | 6–10 tons |
If you’re within these ranges, you’re in the ballpark.
If not, something is way off.
12. Tony’s Final Sizing Verdict
Here’s Tony’s no-nonsense summary:
✔ Square footage is only step one — NOT the final answer
✔ Heat load determines size
✔ Occupancy and equipment matter more than room size
✔ Ceiling height, windows, and lighting change everything
✔ Fresh air requirements add tons of cooling
✔ Ductwork can make or break tonnage
✔ Multiple smaller units often beat one big one
✔ Oversizing is just as dangerous as undersizing
If you size your commercial unit the way Tony does — based on real load, not guesswork — your building will cool evenly, run efficiently, and stay comfortable for years.
In the next blog, Tony will tell you which setup will work best for your building.
