Is 17,400 BTUs Enough? Sizing Tips for Vertical PTAC Units

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If you’re considering a GE Zoneline 17,400 BTU Vertical Packaged Terminal Air Conditioner (PTAC) with electric resistance heat, you’re probably asking yourself one big question:

👉 “Is 17,400 BTUs enough for my space?”

Sizing is the most critical factor when it comes to air conditioning (and heating) performance. Get it wrong, and you’ll either:

Undersize the unit and end up with poor cooling/heating, constant strain, and high energy bills.
Oversize the unit and face short cycling, humidity issues, and wasted money.

In this Savvy guide, I’ll break down:

What BTUs really mean for cooling and heating
How to calculate your room size vs. BTU needs
Special factors (climate, insulation, ceiling height, occupancy)
Why vertical PTACs are different from wall-mounted PTACs
Whether 17,400 BTUs is a sweet spot for your project

By the end, you’ll know if this system is a perfect match for your apartment, multi-family unit, or small commercial space.

📏 What Does 17,400 BTUs Mean in HVAC Terms?

BTU stands for British Thermal Unit — a measure of how much heat energy an AC can remove (cooling) or add (heating) in one hour.

Cooling BTUs = the unit’s ability to absorb heat from indoor air and reject it outside.
Heating BTUs (in electric resistance systems) = how much heat the system can generate using electric coils.

💡 1 ton of AC capacity = 12,000 BTUs/hour.
So, a 17,400 BTU system = roughly 1.5 tons of cooling power.

That means it’s larger than your typical 9,000–12,000 BTU PTAC (common in hotels and small apartments), but smaller than a 24,000 BTU (2-ton) system designed for bigger floorplans.

🏠 How Many Square Feet Can 17,400 BTUs Cover?

As a rule of thumb:

20 BTUs per square foot is the general baseline for cooling capacity in residential spaces .

Using that:

17,400 ÷ 20 = ~870 sq. ft.

👉 In ideal conditions, this unit could cover 800–900 sq. ft. comfortably.

But reality isn’t that simple. Several factors push that number up or down. Let’s break them down.

🌎 Factor 1: Climate Zone

Where you live dramatically impacts cooling needs:

Hot & Humid (Texas, Florida, Southeast): You may need 25–30 BTUs per sq. ft. because the unit works harder to remove moisture.
Mild (Pacific Northwest, Northern California): You may need closer to 18 BTUs per sq. ft.
Cold Winters (Midwest, Northeast): Heating demand often outweighs cooling. With electric resistance heat, expect higher electricity costs.

📌 Example:
An 850 sq. ft. apartment in Houston, TX might require closer to 21,000–22,000 BTUs, while the same size in Portland, OR could be fine with 17,400 BTUs.

👉 Savvy takeaway: Always check your ASHRAE climate zone before locking in capacity .

🧱 Factor 2: Insulation & Building Materials

How your building is constructed is just as important as size.

Well-insulated buildings (newer apartments, energy-efficient retrofits): Hold cool air longer → need fewer BTUs.
Poor insulation / older brick / drafty windows: Leak cool air → need more BTUs.

💡 Energy Star reports that poor insulation can increase cooling loads by 20–30% .

👉 If your space is poorly insulated, 17,400 BTUs might feel like 14,000 in practice.

📐 Factor 3: Ceiling Height

Standard calculations assume 8 ft. ceilings. If yours are higher, you’ve got more cubic footage to condition.

Formula:

📌 Example:

850 sq. ft. apartment, 10 ft. ceilings:
20 BTU × 850 × (10 ÷ 8) = 21,250 BTUs

👉 In this case, 17,400 BTUs may not cut it unless your insulation is excellent.

👥 Factor 4: Occupancy & Heat-Producing Appliances

People generate heat — and so do your appliances.

Add 600 BTUs per additional person beyond 2
Kitchens add ~4,000 BTUs (oven + stove + refrigerator)
Home offices with multiple computers/equipment can add ~1,500 BTUs

👉 If you’re cooling a studio with one person, 17,400 BTUs is plenty.
👉 If it’s a 2-bedroom with 3–4 people and a kitchen, you may need more.

🪟 Factor 5: Sunlight & Exposure

South- and west-facing rooms absorb more solar heat.

Add 10% BTUs for sunny rooms
Subtract 10% for shaded/north-facing spaces

So, that 870 sq. ft. estimate might need to be bumped up to ~950 sq. ft. equivalent load in a sunny apartment.

🧾 Putting It Together: A Real-World BTU Calculation

Let’s run through an example:

1-Bedroom Apartment

Size: 800 sq. ft.
Location: Atlanta, GA (humid climate)
Ceiling height: 9 ft.
Occupants: 2 adults + 1 child
Appliances: Kitchen included
Sunlight: Mostly south-facing windows

Calculation:

Base load: 20 BTUs × 800 = 16,000
Climate factor (+15%): +2,400
Ceiling factor (9/8 = +12%): +1,920
Occupancy (extra 1 person): +600
Kitchen: +4,000
Sunlight (10%): +2,400

Total: ~27,300 BTUs needed.

👉 Verdict: 17,400 BTUs would be undersized for this specific setup.

But in a similar 800 sq. ft. unit in Seattle with no extra people or kitchen load, the same 17,400 BTU unit would be perfectly sized.

🧩 Why Vertical PTACs Are Different from Standard PTACs

Now, let’s address the vertical PTAC (VPAC) difference.

Unlike standard PTACs that mount through an exterior wall, vertical PTACs are installed in a closet with duct connections, distributing conditioned air to multiple rooms.

Benefits of vertical PTACs:

Serve larger areas than single-room PTACs
Quieter, since the unit is tucked away in a closet
Better for apartments, hotels, or multi-room layouts

👉 This means a 17,400 BTU vertical PTAC can stretch further than a wall PTAC, because it distributes air more efficiently across spaces.

🔌 Heating Considerations: Electric Resistance vs. Heat Pump

This GE Zoneline model uses electric resistance heat, not a heat pump.

Pros: Simple, reliable, consistent heat output
Cons: Less efficient than heat pumps → higher electricity bills in winter

📌 According to the U.S. Department of Energy, electric resistance heating can cost 2–3 times more to operate than heat pumps .

👉 If you’re in a cold northern climate, 17,400 BTUs of electric resistance may not be enough for heating needs. But in mild winters, it’s sufficient.

💡 When Is 17,400 BTUs the Right Choice?

This system is a great fit if:

Your space is 700–900 sq. ft. with average ceilings
You live in a mild to warm climate (not extreme humidity/heat)
You want multi-room comfort from a vertical PTAC setup
You value quiet operation (closet-mounted)

It may not be enough if:

You’re cooling over 900 sq. ft. in a hot climate
Ceilings are higher than 9 ft.
You have high occupant load or lots of appliances
Winters are cold and you rely heavily on electric resistance heating

📊 Quick Reference Sizing Table (Savvy’s Cheat Sheet)

Space Size	Avg. Climate	Hot/Humid Climate	Notes
600–700 sq. ft.	✅ Perfect fit	✅ Still works	Ideal efficiency zone
800–900 sq. ft.	✅ Works well	⚠️ May struggle	Climate + insulation critical
900–1,000 sq. ft.	⚠️ Borderline	❌ Undersized	Consider 24,000 BTU
1,000+ sq. ft.	❌ Too small	❌ Too small	Upgrade needed