WindowENERGY STAR
Keystone KSTAW12CE
Cooling
12,000 BTU
Covers
550 ft²
Efficiency
12 CEER
Noise
58 dB
$360 est.
via partner retailers Window ENERGY STAR
LG LW1521ERSM 15,000 BTU
by LG · Model LW1521ERSM
The go-to large-room smart unit: 15K BTU, Wi-Fi via ThinQ, and whole-floor coverage to 800 sq ft.
Cooling
15,000 BTU
Covers
800 ft²
Efficiency
11.8 CEER
Noise
53 dB
$549 est.
typical street price · via Amazon Is 15,000 BTU right for your room? Run the sizing calculator
Strengths & trade-offs
Pros
- Cools up to 800 sq ft
- ThinQ app and voice control
- 4-way air deflection
Cons
- Needs a large window
- Heavy 100+ lb install
What the LG LW1521ERSM 15,000 BTU costs to run
Estimated from this unit's 11.8 CEER rating at 8 hours/day of cooling, using average residential electricity rates for each US climate zone. Your usage and utility rate will shift these numbers — run the calculator for your exact room.
| Climate zone | Example regions | Est. cost / month |
|---|---|---|
| Cool North | Pacific NW, Upper Midwest, New England | $49 /mo |
| Mixed / Temperate | Mid-Atlantic, Midwest, Mountain | $52 /mo |
| Hot & Humid | Southeast, Gulf Coast, Texas | $43 /mo |
| Hot & Dry | Southwest, Desert | $46 /mo |
Full specifications
| Type | Window air conditioner |
| Cooling capacity | 15,000 BTU |
| Rated coverage | 800 ft² |
| Efficiency | 11.8 CEER |
| Noise (low) | 53 dB |
| Smart features | App, Voice, Scheduling |
| ENERGY STAR | Yes |
| Model number | LW1521ERSM |
| Typical street price | $549 |
Specs from manufacturer data; price and ratings are snapshots and may vary. See how we evaluate.
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Cooling
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Covers
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Efficiency
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Noise
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Cooling
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Efficiency
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Noise
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