Keystone 18,000 BTU Inverter Window Air Condit… | compare.ac
Keystone 18,000 BTU Inverter Window Air Conditioner vs LG 18,000 BTU Smart Wi-Fi Enabled Window AC (LW1821ERSM)
The Keystone 18,000 BTU Inverter Window Air Conditioner and the LG 18,000 BTU Smart Wi-Fi Enabled Window AC (LW1821ERSM) side by side on one honest scale: cooling, room coverage, noise, energy rating and live price, with which one actually fits your room. Every number is the manufacturer's own or a live retailer price. We never invent a spec.
The verdict
For your 500 sq ft room, neither is an ideal fit: the Keystone 18,000 BTU Inverter Window Air Conditioner is more cooling than the room needs and the LG 18,000 BTU Smart Wi-Fi Enabled Window AC (LW1821ERSM) is more cooling than the room needs. On the numbers, the LG 18,000 BTU Smart Wi-Fi Enabled Window AC (LW1821ERSM) is cheaper at $478. Compare their specs side by side below, or try a different room size.
Both units are scored on the exact same scale, from the manufacturer's own published specs and the live retailer price where we have one. Room fit uses the official ENERGY STAR sizing chart, or an estimate from cooling power when a maker publishes no coverage. Where the two efficiency scales are not comparable, we never crown a winner. Nobody can pay for placement.
Should I buy the Keystone 18,000 BTU Inverter Window Air Conditioner or the LG 18,000 BTU Smart Wi-Fi Enabled Window AC (LW1821ERSM)?
The Keystone 18,000 BTU Inverter Window Air Conditioner and the LG 18,000 BTU Smart Wi-Fi Enabled Window AC (LW1821ERSM) are close alternatives: the LG 18,000 BTU Smart Wi-Fi Enabled Window AC (LW1821ERSM) is cheaper at $478. Set your room size to see which one fits it better.
Which is cheaper, the Keystone 18,000 BTU Inverter Window Air Conditioner or the LG 18,000 BTU Smart Wi-Fi Enabled Window AC (LW1821ERSM)?
The LG 18,000 BTU Smart Wi-Fi Enabled Window AC (LW1821ERSM) is cheaper at $478, versus $679.99 for the Keystone 18,000 BTU Inverter Window Air Conditioner. That is the current live retailer price where we have one, otherwise the listed price.
Is now a good time to buy the Keystone 18,000 BTU Inverter Window Air Conditioner or the LG 18,000 BTU Smart Wi-Fi Enabled Window AC (LW1821ERSM)?
The LG 18,000 BTU Smart Wi-Fi Enabled Window AC (LW1821ERSM) is currently at the lowest price we have tracked at Abt Electronics since Jul 25, 2026 ($478). The Keystone 18,000 BTU Inverter Window Air Conditioner does not have a verified current low in our available history. A dated observation from our own daily price history, not a manufacturer sale.
Do I need a professional to install the Keystone 18,000 BTU Inverter Window Air Conditioner or the LG 18,000 BTU Smart Wi-Fi Enabled Window AC (LW1821ERSM)?
Neither needs a professional: both are window units you set up yourself (usually no permit).
How much cooling power do I need for my room?
A common US rule of thumb for a standard, reasonably insulated room with an 8-foot ceiling is about 20 BTU per hour per square foot, so a 300 sq ft room is often quoted around 6,000 BTU and a 500 sq ft room around 10,000 BTU. compare.ac instead sizes against the official ENERGY STAR room air conditioner chart, which is not a flat rate: it recommends about 7,000 BTU for that same 300 sq ft room and about 12,000 BTU for a 500 sq ft room, then adjusts up for a hot or humid climate and down for a mild one once you pick your region. Add capacity for a sunny west-facing or top-floor room, a kitchen, or extra people who are regularly in it. Undersizing means the unit runs flat out and never cools; oversizing short-cycles and leaves the room cool but clammy.
What will it cost to run, and what do the efficiency ratings mean?
Running cost is driven by efficiency: CEER on window and portable units, and SEER2 on mini-splits. Higher is better on both, but they are separate scales and a SEER2 number cannot be read as a ratio against a CEER number. Directionally, an efficient inverter mini-split is the cheapest type to run, while a single-hose portable can cost roughly two to three times as much for the same comfort, because much of its capacity is lost back through the exhaust hose. For window and portable units that ENERGY STAR certifies, we go a step further and show an estimated dollars-per-year figure, taken from the model's published annual energy use (a DOE test that assumes about 750 hours of cooling a year) priced at the average US residential electricity rate. It is a standardized figure for comparing units, not a personal bill: your real cost depends on how much you run it, your local electricity rate, and your climate. Mini-splits are usually the most efficient of all but are rated on SEER2, so we do not convert those to a dollar figure, and a missing running cost is a data gap, never a sign a unit is worse.
