Model
Comfort Aire RXTS-121A
Rank #231 means 230 of the 404 room air conditioner models we track cost less to run each year; the 43rd efficiency percentile means it uses less energy for its size than 43% of those models.
What does the Comfort Aire RXTS-121A cost to run per year?
Do the math and the Comfort Aire RXTS-121A's $111/yr puts it at rank #231 of 404, right around the class average. It uses 38% less energy than the U.S. federal standard model in its class, which would cost about $180/yr to run, a saving of roughly $69 a year. Adjusted for size, it is more efficient than 43% of room air conditioner models we track, a middling result. The CEER figure of 15 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 Century RXTS-121A at $111/yr runs a little cheaper and the Danby DAC120ECBIWDB at $111/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 Comfort Aire RXTS-121A's $111/yr adds up to roughly $1110 in electricity alone, before purchase price or repairs.
Also sold as: Black+Decker BD12NWES.
By the numbers
The Comfort Aire RXTS-121A 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 $111/yr, here is what the Comfort Aire RXTS-121A adds up to before purchase price, water, or repairs enter the math.
Left running for a decade at today's US average rate, the Comfort Aire RXTS-121A costs about $1110. That is roughly $690 less than a standard model in its class, which would run closer to $1800 over the same ten years.
How the Comfort Aire RXTS-121A compares
The room air conditioner class we track runs from $51 to $389 a year. At $111/yr, it runs about $12 a year above the class median of $99, and it is about $60 a year more than the cheapest room air conditioner to run at $51. Against the US federal standard model for its class at about $180/yr, the Comfort Aire RXTS-121A uses 38% less energy.
What drives its running cost
At 12000 BTU/hr, the Comfort Aire RXTS-121A is a mid-size room air conditioner for its class, which spans 5000 to 34100 BTU/hr with a median of 10100 BTU/hr, right in the middle of the capacity range, so capacity is roughly a wash compared with the rest of the class. Beyond size, its CEER of 15, above 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). CEER captures cooling output per watt, including standby power; a higher CEER means less electricity for the same BTU of cooling.
- BTU cooling capacity. A higher-BTU unit is sized for a bigger room and generally uses more electricity per hour of operation than a smaller unit, regardless of efficiency.
- Thermostat and mode usage. Running on a fixed low temperature around the clock uses far more energy than using a thermostat setting, eco mode, or a timer to match cooling to when the room is actually occupied.
Common questions
Is the Comfort Aire RXTS-121A cheap to run?
It is about average. At $111 a year it ranks #231 of 404 room air conditioner models we track, close to the middle of its class on running cost.
How much does the Comfort Aire RXTS-121A cost per month?
Roughly $9.28/mo, spreading the $111/yr estimate evenly across twelve months at $0.1856/kWh. Actual monthly bills swing with your rate and usage pattern.
How is this running-cost figure calculated?
We take the model's published annual energy use of 600 kWh from ENERGY STAR and multiply it by the US average residential electricity rate of $0.1856/kWh, giving about $111 a year. It is an electricity-only estimate and does not include purchase price, water, or installation.
How efficient is the Comfort Aire RXTS-121A for its size?
43rd percentile once size is factored in, a fairly typical result for the class.
Cheaper to run in the same class
Source
ES_0017771_RXTS-121A_07272023175325_80167537View certified room air conditioner listingsENERGY STAR data as of July 2026Comfort Aire and RXTS-121A 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.