One window unit, three bedrooms.
We installed an LG 5,000 BTU window air conditioner in the living room of a three-bedroom apartment. Here's the math on whether a unit that small can do anything for the rest of the place — and what the data actually says.
A small unit in a big-enough apartment
The unit going in is one of LG's standard 5,000 BTU window models (the LW5000-series — LW5023, LW5024, LW5016, and similar variants are all rated identically). It's a compact, mechanically-controlled unit designed and marketed for one purpose: cooling a single small room. LG's own spec sheet is explicit about this — the company rates the unit for rooms up to 150 square feet, positioning it for bedrooms, home offices, and dorm rooms rather than open living areas.
It's now sitting in the living room window of a three-bedroom apartment — a space that, by definition, includes a living room, a kitchen, a hallway, and three separate bedrooms behind closed doors. That's the setup worth examining: can 5,000 BTU of cooling capacity, installed in one room, do anything meaningful for the square footage around it?
Running the numbers
BTU sizing for room air conditioners follows a well-established rule of thumb, backed by ASHRAE's standard sizing guideline of roughly 20 BTU per square foot for a room with standard 8–9 foot ceilings. Energy Star's guidance adds adjustments on top of that baseline for kitchens, sun exposure, and occupancy — but the core number is what matters here.
Even using the most conservative national averages, the rated coverage area of a 5,000 BTU unit accounts for roughly a tenth of a typical three-bedroom apartment's total floor space. Three-bedroom apartments in the U.S. typically range from 1,000 to 1,500 square feet, and that's before factoring in that the living room itself — the one room the unit is actually rated to cool — is very often larger than 150 square feet on its own in a three-bedroom layout.
What the coverage radius actually looks like
Numbers on their own undersell the gap. Laid out against an actual three-bedroom floor plan, the unit's rated 150 sq ft reach barely extends past the living room — and even there, it's pushing the edge of what it's designed for.
It's not just square footage
Square footage undersells the problem, if anything. A window AC has no ductwork — it cools by recirculating the air directly in front of it. Three structural realities work against it ever reaching the bedrooms:
No air path to closed-door rooms
Cool air doesn't travel down hallways and under doors in any meaningful volume. The unit cools the air it can pull in and push out directly — once that air has to turn a corner, cross a kitchen, and slip under a bedroom door, almost none of the actual cooling effect survives the trip.
Oversizing a room doesn't help neighboring rooms
It might be tempting to think "if it can't cool the apartment, just let it run longer or set it colder." It won't help. An undersized window AC just runs continuously trying to reach its setpoint, which increases electricity bills by 30–50% and wears out the compressor — without actually closing the distance to rooms it isn't rated for.
Living rooms in 3BR apartments often exceed 150 sq ft on their own
Consumer Reports' independent lab testing puts this in concrete terms: a living room or family room in the 350–550 sq ft range needs a unit in the 9,800–12,500 BTU class, especially with an open floor plan connecting to a kitchen or dining area — which is common in three-bedroom units. A 5,000 BTU unit may be working hard just to hold its own room steady, before the rest of the apartment even enters the picture.
Not nothing — just not "whole apartment"
None of this means the unit is useless. It just means its job description is narrow. Realistically, here's what a 5,000 BTU unit in the living room window delivers:
| Effect | Likely outcome |
|---|---|
| Living room temperature | Noticeably cooler, especially within ~10–15 ft of the unit |
| Living room humidity | Reduced — window ACs dehumidify as a side effect of cooling |
| Kitchen / dining (if open-plan) | Marginal relief at best, fading fast with distance |
| Hallway | Essentially no measurable change |
| Bedrooms with doors closed | No meaningful change — doors block the airflow path entirely |
| Overall apartment temperature | No material change to the average |
If the doors are left open and a fan is used to actively push air down the hallway, there may be a marginal softening of bedroom temperatures — but that's circulation, not cooling capacity, and it won't get close to what a properly sized unit per room would do.
What reviewers say about this exact unit
A couple of hands-on reviews of the LG 5,000 BTU window line — useful for seeing the unit's actual airflow, noise level, and control layout before judging what it can and can't do.
How this unit actually goes into the window
For anyone doing this install themselves, LG's official walkthrough covers the window kit, the L-brackets, and the slight backward tilt the unit needs for proper drainage — the same install process used for the 5K, 6K, 8K, and 10K BTU window line.
If the goal is the whole apartment, not just the living room
None of these require ripping anything out — they're just sized for the actual job.
One unit per bedroom
A second and third small window or portable AC (5,000–8,000 BTU depending on room size) in each bedroom solves the "doors closed" problem directly, since each room gets its own source instead of relying on hallway drift.
Right-size the living room unit
If the living room itself is 300+ sq ft or open to the kitchen, swap the 5,000 BTU unit for one in the 8,000–12,000 BTU range — sized to actually finish the job in that one room before worrying about the rest of the apartment.
Ductless mini-split, multi-zone
A multi-zone mini-split system can condition several rooms from one outdoor compressor, each with its own indoor head — the closest a non-central-air apartment can get to whole-unit cooling.
Circulation fans as a stopgap
Not a real fix, but a box fan in the hallway doorway, pulling cooled air from the living room toward the bedrooms, can take the edge off on milder days — at no cost beyond the fan itself.
Further reading
The doubt was right
A 5,000 BTU unit covers roughly 150 square feet by design — about a tenth of a typical three-bedroom apartment's footprint, and quite possibly less than the living room it's actually sitting in. It will make a real, noticeable difference in that one room. It will not, and structurally cannot, bring down the temperature of bedrooms behind closed doors down the hall. Anyone going in expecting whole-apartment relief from this unit should adjust expectations to "living room relief" — and budget for additional units if the rest of the apartment needs to come down in temperature too.
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