LG LW2521ERSM 24,500 BTU Smart Window AC Review: Big-Space Power
A 24,500 BTU smart window air conditioner on 230/208V power with LG ThinQ app control, Alexa and Hey Google support, a remote and 24-hour timer. Built for very large rooms and open floors.
By Daniel Brooks
Updated October 8, 2026
The LG LW2521ERSM 24,500 BTU Smart Window Air Conditioner is one of the largest window units you can buy, with LG listing coverage of up to 1,560 square feet. It runs on 230/208V power and adds LG ThinQ app control with Amazon Alexa and Hey Google support. Among conventional window air conditioners, it is aimed at very large rooms, open-plan floors or several connected rooms.
This is not a plug-and-play unit. It needs a 230V circuit, a large window and a team to install it. The question is whether a single high-capacity window unit is the right way to cool your space. We evaluated it based on the manufacturer’s specifications.
Our Verdict
This LG is a serious cooling machine for big spaces. Its strongest points are 24,500 BTU of cooling, ThinQ app control with voice assistant support, a remote, 3 cooling and fan speeds, a 24-hour on/off timer, 4-way air deflection, a filter check reminder and Auto Restart. LG also lists dehumidification of up to 1.8 pints per hour.
The trade-offs are significant. It weighs 132 pounds, needs a 230/208V outlet, has no inverter, and the specification sheet lists 61 dB. It holds 3.8 stars from 58 ratings. If you have the power supply and the window for it, and need to cool a very large area from one point, it is worth considering.
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Key Specifications
| Feature | Specification |
|---|---|
| Brand | LG |
| Model | LW2521ERSM |
| Type | Smart window air conditioner |
| Cooling Capacity | 24,500 BTU |
| Room Size (listed) | Up to 1,560 sq. ft. (39′ x 40′) |
| Efficiency | 10.3 (listed as SEER) |
| Noise Level | 61 dB (specification); as low as 50 dB in low mode (manufacturer) |
| Voltage / Power | 230/208V, 2370W |
| Window Fit | 29″ to 41″ wide, 19″ minimum height |
| Dimensions | 28.11″D x 25.98″W x 17.68″H |
| Weight | 132 pounds |
| Fan Speeds | 3 cooling and fan speeds |
| Dehumidification | Up to 1.8 pints per hour |
| Smart Controls | LG ThinQ app, Amazon Alexa, Hey Google, remote |
| Timer | 24-hour on/off |
| Compressor | Rotary, no inverter |
| Refrigerant | R-32 |
| Warranty | 1 year limited |
Cooling Capacity and Room Size
LG rates the LW2521ERSM at 24,500 BTU for rooms up to 1,560 square feet, describing a space of about 39′ x 40′. LG also suggests it can keep multiple small rooms on the same floor cool, though in practice a single window unit cools the room it sits in best, and airflow into side rooms depends heavily on your layout.
At this capacity, the main risk is oversizing. A unit this powerful in a room that does not need it will cool quickly and shut off before it removes much moisture, which can leave the space clammy. It makes the most sense in a genuinely large open room, a big basement or a converted garage.
ENERGY STAR publishes this general guide for sizing a room air conditioner by floor area:
| Room Size (sq ft) | Cooling Capacity (BTU/hr) |
|---|---|
| 100 to 150 | 5,000 |
| 150 to 250 | 6,000 |
| 250 to 300 | 7,000 |
| 300 to 350 | 8,000 |
| 350 to 400 | 9,000 |
| 400 to 450 | 10,000 |
| 450 to 550 | 12,000 |
| 550 to 700 | 14,000 |
| 700 to 1,000 | 18,000 |
Adjust for your room: reduce capacity by 10 percent for a heavily shaded room, increase it by 10 percent for a very sunny room, add 600 BTU for each regular occupant beyond two, and add 4,000 BTU if the unit cools a kitchen. Source: ENERGY STAR.
At 24,500 BTU, this unit is above the largest size on the chart, which tops out at 18,000 BTU for 700 to 1,000 square feet. LG’s 1,560 square foot claim is therefore beyond what the chart covers, so treat it as a best-case figure for an open, well-insulated space.
Installation and Fit
The listed window opening is 29 to 41 inches wide with a minimum height of 19 inches. That rules out many standard bedroom windows, so measure carefully. The cabinet is 28.11 inches deep, 25.98 inches wide and 17.68 inches tall, and the unit weighs 132 pounds.
This is a job for at least two strong people, and a professional installer is worth considering. Use the included window installation kit and any support bracket the manual specifies, since a unit this heavy must be fully supported from below. The electrical supply must be a 230/208V receptacle that matches the plug. Never use an adapter or extension cord, and have an electrician confirm the circuit if you are unsure.
Noise, Energy Use and Efficiency
LG says the unit runs as low as 50 dB in low mode, while the specification sheet lists 61 dB, likely at higher settings. Expect noticeable sound at full output, which is normal for a unit of this size. In a large living space with normal background noise, that is usually acceptable.
The listing gives an efficiency figure of 10.3, labeled as SEER, and a power draw of 2370 watts. There is no inverter, so the compressor cycles fully on and off. The 24-hour timer and app scheduling are the main tools for limiting running time to when the space is in use.
Controls and Smart Features
LG ThinQ lets you start or stop cooling, change the mode and set the temperature from anywhere. It also works with Amazon Alexa and Hey Google for voice control. For a large space that takes time to cool, starting the unit before you arrive is a genuinely useful feature.
On the unit, a digital control panel handles all settings, and the included remote works from across the room. You get 3 cooling and fan speeds, a 24-hour on/off timer and 4-way air deflection to direct air across a wide area. Auto Restart turns the unit back on after a power failure.
Maintenance and Drainage
The slide-out filter is washable, and a filter check reminder light tells you when it needs cleaning. In a high-capacity unit that moves a lot of air, keeping the filter clean has a big effect on airflow and efficiency, so clean it promptly when the light comes on.
LG lists dehumidification of up to 1.8 pints per hour, which means a meaningful amount of condensate on humid days. The listing does not describe the drainage method, so check the manual for how water is handled. At the end of the season, removing a 132 pound unit is a two-person job, so some owners leave it in place with a cover; follow the manual’s guidance.
Pros and Cons
| Pros | Cons |
|---|---|
| 24,500 BTU for very large spaces | Requires a 230/208V outlet |
| LG ThinQ app with Alexa and Hey Google | Very heavy at 132 pounds |
| Remote, 24-hour timer and Auto Restart | Needs a window at least 29″ wide and 19″ high |
| 4-way air deflection | Specification lists 61 dB |
| Dehumidifies up to 1.8 pints per hour | No inverter compressor |
Who Should Buy It
| Who Should Buy It? | Who Should Look Elsewhere? |
|---|---|
| Very large open rooms or basements | Standard bedrooms or living rooms |
| Homes with a 230V circuit near the window | Homes with only standard outlets |
| Smart home users with Alexa or Google | Windows narrower than 29″ or shorter than 19″ |
| Buyers who want one unit for a big space | Anyone without help for a 132 pound install |
| Garages or workshops with suitable windows | Buyers set on an inverter compressor |
Final Verdict
The LG LW2521ERSM 24,500 BTU Smart Window Air Conditioner delivers enormous cooling capacity with ThinQ app control, voice assistant support, a remote, 24-hour timer and 4-way air deflection. It suits a very large open room, basement or workshop where one powerful unit makes sense. The compromises are a 230/208V power requirement, a 132 pound weight, a large window requirement and no inverter. If your space and wiring are ready, you can check the current price and details for the LG LW2521ERSM 24,500 BTU Smart Window Air Conditioner, or compare other extra large window air conditioners.
Frequently Asked Questions
Does the LG LW2521ERSM need a special outlet?
Yes. It runs on 230/208V power and needs a matching receptacle. It will not work on a standard household outlet, and you should not use an adapter.
What window size does it need?
The listed opening is 29 to 41 inches wide with a minimum height of 19 inches. Measure carefully, since many standard windows are too small.
Can I control it with Alexa?
Yes. LG ThinQ supports control from your phone, and the unit works with Amazon Alexa and Hey Google. A remote is also included.
How heavy is it?
It weighs 132 pounds and measures 28.11 inches deep. Plan on at least two strong people or a professional installer.
About the author
Daniel Brooks is a home cooling editor at WikiCooling, covering window, portable, through-the-wall and mini-split air conditioners, fans, and dehumidifiers. He researches cooling capacity, energy efficiency, noise levels, installation requirements, and buyer feedback to help homeowners choose the right unit for their room size, climate, and budget.