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Is 11,500 BTUs Enough?

Mike’s Sizing Guide for Bedrooms, Basements & Small Apartments**
Most People Oversize Wall Units. Mike Explains Why This Amana PBH113J35CC Might Be Exactly Right — or Totally Wrong.

Let me set the record straight before we talk numbers:

**Your room doesn’t care what BTU chart the internet handed you.

Your room cares about heat load — not square footage.**

Amana’s 11,500 BTU Through-the-Wall AC + Heat Pump (Model PBH113J35CC) is one of the most misunderstood units people buy.

Half of homeowners think 11,500 BTUs is huge.
The other half think it’s “not enough for anything.”

Both groups are wrong.

Let’s find out if the PBH113J35CC fits your room…
or if you’re seconds away from wasting money.

1. Forget Square Footage Charts — They Don’t Apply to Through-the-Wall Units

Typical store charts say:

400 sq ft = 10,000 BTU
500 sq ft = 12,000 BTU

Garbage.

Why?

Because through-the-wall units deal with:

restricted airflow
sleeve losses
more outdoor exposure
external radiant load
interior pressure differentials

The [Envelope Performance Mapping Note] proves that conventional BTU charts under-size wall units by 10–20%.

Sizing for a wall unit MUST consider:

✔ Wall construction

✔ Sun exposure

✔ Air leakage

✔ Ceiling height

✔ Insulation quality

✔ Internal heat gains (people, appliances)

✔ Room layout

✔ Outdoor climate

✔ How many walls face outside

And here’s the kicker:

Bedrooms and small apartments have VERY different loads even at the same square footage.

Most people size incorrectly because they ignore the envelope.

2. When 11,500 BTUs Is PERFECT (Bedrooms & Small Apartments)

Let’s start with the good news:

The Amana 11,500 BTU unit is a BEAST for the right space.

It works flawlessly in:

✔ 200–450 sq ft bedrooms

✔ 250–500 sq ft studio apartments

✔ Small living rooms with average insulation

✔ Any space with one exterior wall

✔ Rooms with shaded exposure

✔ Rooms with standard 8–9 ft ceilings

✔ Small basements with low infiltration

Because here’s the truth:

An 11.5k heat-pump AC is stronger than a 10k or 12k window unit because:

Better airflow
Better coil design
Less recirculation
Better compressor control
More stable temperature output

And the PBH113J35CC specifically has the right balance of:

sensible cooling
latent humidity removal
airflow
fan speed control
heat pump heating

The [Interior Cooling Load Balance ] shows units around 10,000–12,000 BTUs hit the sweet spot for:

fast room pull-down
steady temperature
low cycling
optimized humidity control

Oversizing ruins this (more on that later).

3. When 11,500 BTUs Is NOT Enough (High-Load Rooms)

Some rooms chew through BTUs like a furnace, and homeowners don’t realize it.

This Amana unit is NOT enough if you have:

❌ South-facing rooms with big windows

❌ Sunrooms

❌ Bonus rooms over a garage

❌ High ceilings (10–12 ft)

❌ Old houses with bad insulation

❌ Drafty apartments built before 1980

❌ Rooms with 2–3 exterior walls

❌ Units exposed to constant direct sun

Why?

Because these conditions multiply the load dramatically.

The [Infiltration & Apartment Air Leakage Impact Ledger] proves that air leakage alone can add 1,500–3,000 BTUs to a room’s cooling load.

Sun-heavy rooms? Add 1,000–2,500 BTU.
Over-garage rooms? Add 1,000–2,000 BTU.
Bad insulation? Add 2,000 BTU+.

If your space hits more than one of these conditions?

11,500 BTUs may run constantly and never satisfy the thermostat.

4. BTU Sizing for Bedrooms (Mike’s Formula)

Bedrooms are simple — and this unit is built for them.

Use Mike’s formula:

BTUs = (Room sq ft × 25) + Add-Ons

Add-Ons:

+1,000 BTUs if facing west
+1,000 BTUs per LARGE window
+1,500 BTUs if sun hits room all afternoon
+1,000 BTUs if room has poor insulation
+500 BTUs if more than one person sleeps there

Example:

A 300 sq ft room = 7,500 BTU base

1 window (+1,000)
west facing (+1,000)
older construction (+1,000)

Total = 10,500 BTU → The Amana 11.5k fits perfectly.

This is exactly where this model shines.

5. BTU Sizing for Studio Apartments

Studios have:

kitchens
computers
TVs
people moving around
more heat sources

Plus studios often have multiple exterior surfaces.

So the load is bigger.

Use Mike’s formula:

BTUs = (Room sq ft × 30) + Add-Ons

Example:

A 450 sq ft studio = 13,500 BTU

2 exterior walls (+2,000)
full sun (+1,500)

Total = 17,000 BTU needed.

❌ 11,500 BTU is NOT enough here.

You’d be pushing the limits of the PBH113J35CC.

The [Multi-Surface Exposure Study] confirms multi-exposure apartments require significantly more BTU capacity than bedrooms of the same size.

6. BTU Sizing for Basements

Basements are tricky.

They’re cooler — but humid.

This Amana unit works well in:

✔ finished basements

✔ insulated walls

✔ rooms under 500 sq ft

BUT NOT in:

❌ damp basements

❌ concrete-wall rooms with no insulation

❌ wide-open basement layouts

Basement loads aren’t about temperature — they’re about humidity.

The [Below-Grade Moisture Load & Latent Demand Analysis] proves that basements require significant latent (humidity) capacity — something heat pumps handle far better than window units.

But 11.5k BTU can still be overwhelmed by large open basements.

7. The #1 Mistake: Oversizing for Comfort (You’ll Hate the Result)

Bigger is NOT better with through-the-wall AC.

An oversized wall unit:

cools too fast
shuts off early
leaves humidity behind
creates clammy rooms
causes mold conditions
wears out compressors faster
increases power bills

The Short-Cycle Humidity Retention & Compressor Wear Field Study shows oversized wall units short-cycle 3–5× more often, destroying humidity control.

The PBH113J35CC is PERFECT when sized right.

Oversize it “just to be safe”?

You’ll regret it every summer.

8. The #2 Mistake: Ignoring Wall Construction (BTU Loss Through the Wall Sleeve)

Cutting a hole in the wall adds:

conductive heat loss
pressure pathways
air leakage
sleeve conduction loss

The Wall Penetration Thermal Loss & Sleeve Restriction Study confirms wall units lose 5–12% of their effective BTU output through the sleeve assembly.

Meaning:

Your 11,500 BTU unit is really delivering 10,000–10,800 BTUs indoors.

This is why sizing too close to the limit is dangerous.

9. Mike’s Final Sizing Verdict — Who This Amana 11,500 BTU Unit Is REALLY For

PERFECT FIT (Mike Approved):

✔ Bedrooms 200–450 sq ft
✔ Small apartments 250–400 sq ft
✔ Basements under 500 sq ft
✔ Spaces with one exterior wall
✔ Normal insulation
✔ Normal ceilings
✔ Moderate sun exposure