Model
Keystone KSTAW242WA
Rank #381 means 380 of the 404 room air conditioner models we track cost less to run each year; the 5th efficiency percentile means it uses less energy for its size than 5% of those models.
What does the Keystone KSTAW242WA cost to run per year?
Among the 404 room air conditioner models we track, the Keystone KSTAW242WA's $251/yr running cost ranks it #381, in the pricier fifth of the class. It uses 41% less energy than the U.S. federal standard model in its class, which would cost about $426/yr to run, a saving of roughly $175 a year. Capacity-normalized, it ranks ahead of just 5% of room air conditioner models we track, a clearly below-average result. The CEER figure of 13.3 on this model captures combined energy efficiency ratio, the main efficiency lever ENERGY STAR tracks for this class.
Immediately around it on the leaderboard, the Keplerx KBRC24RSVE2 at $251/yr runs a little cheaper and the Midea MAW24R2VWT at $251/yr runs a little more, a sense of how tightly models are packed at this point in the ranking. A room air conditioner typically stays in service for somewhere around 10 years; over that span, the Keystone KSTAW242WA's $251/yr adds up to roughly $2510 in electricity alone, before purchase price or repairs.
Also sold as: Comfort Aire RADS-253R03.
By the numbers
The Keystone KSTAW242WA normalized against its whole class, so each figure means something.
What it costs you over time
Running cost is an every-year number, so it compounds. At $251/yr, here is what the Keystone KSTAW242WA adds up to before purchase price, water, or repairs enter the math.
Left running for a decade at today's US average rate, the Keystone KSTAW242WA costs about $2510. That is roughly $1750 less than a standard model in its class, which would run closer to $4260 over the same ten years.
How the Keystone KSTAW242WA compares
The room air conditioner class we track runs from $51 to $389 a year. At $251/yr, it runs about $152 a year above the class median of $99, and it is about $200 a year more than the cheapest room air conditioner to run at $51. Against the US federal standard model for its class at about $426/yr, the Keystone KSTAW242WA uses 41% less energy.
What drives its running cost
At 24000 BTU/hr, the Keystone KSTAW242WA is a large room air conditioner for its class, which spans 5000 to 34100 BTU/hr with a median of 10100 BTU/hr, among room air conditioner models, bigger capacity is the most common reason a running-cost figure lands on the high side, all else being equal. Beyond size, its CEER of 13.3, below the class median of 15, is the class's own efficiency yardstick, combined energy efficiency ratio, and it is what separates two similarly sized models with different running costs.
- Combined Energy Efficiency Ratio (CEER). Two units with the same BTU rating can post very different running costs, and CEER is the figure that explains most of that gap.
- BTU cooling capacity. BTU rating scales with room size, and it is usually the first driver of an air conditioner's running cost, ahead of its CEER figure.
- Thermostat and mode usage. How the unit is actually operated, thermostat cycling versus a fixed setting, moves real electricity use more than the rated BTU or CEER figure alone.
Common questions
Is the Keystone KSTAW242WA cheap to run?
Its $251/yr running cost, rank #381 of 404, is above what most room air conditioner models we track cost to run, so this is not one of the cheaper picks on electricity alone.
How much does the Keystone KSTAW242WA cost per month?
About $20.93 a month, which is the $251 annual estimate spread across twelve months at the US average rate of $0.1856/kWh. Your own bill scales with your local electricity rate and how heavily you use it.
How is this running-cost figure calculated?
The formula is annual kWh times price per kWh: 1,353 kWh from ENERGY STAR times the US average of $0.1856/kWh comes to about $251 a year. It covers electricity only, not the purchase price, water, or installation.
How efficient is the Keystone KSTAW242WA for its size?
5th percentile once size is factored in. That means its size-adjusted efficiency is not the main reason for the running-cost figure above; its capacity plays a large role too.
Cheaper to run in the same class
Source
ES_1055302_KSTAW242WA_11142024120904_80206320View certified room air conditioner listingsENERGY STAR data as of July 2026Keystone and KSTAW242WA are used here for identification only and are not endorsements. Figures are computed by WattWise Labs from public ENERGY STAR data, not measured in our own lab.