Model
Keystone KSTAW12INV-HC
Rank #313 means 312 of the 404 room air conditioner models we track cost less to run each year; the 8th efficiency percentile means it uses less energy for its size than 8% of those models.
What does the Keystone KSTAW12INV-HC cost to run per year?
The Keystone KSTAW12INV-HC costs about $126 a year to run, more than most of the 404 room air conditioner models we track; it ranks #313. It uses 36% less energy than the U.S. federal standard model in its class, which would cost about $196/yr to run, a saving of roughly $70 a year. Efficiency-wise, once size is accounted for, it lags most of the class, ahead of only 8% of the models we track. At a CEER of 13.3, its combined energy efficiency ratio is the single figure that best explains how it earns its running-cost number.
Immediately around it on the leaderboard, the Tcl W14WC72-B at $122/yr runs a little cheaper and the Lubeck 57H-ID0-B12HRFN8BCL0 at $126/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 KSTAW12INV-HC's $126/yr adds up to roughly $1260 in electricity alone, before purchase price or repairs.
Also sold as: Lubeck 57H-ID0-B12HRFN8BCL0, Midea MAW12HV1CWT, Midea MAW12HV1CWT-A, Midea MWAUQB-12HRFN8-BCL0.
By the numbers
The Keystone KSTAW12INV-HC 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 $126/yr, here is what the Keystone KSTAW12INV-HC 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 KSTAW12INV-HC costs about $1260. That is roughly $700 less than a standard model in its class, which would run closer to $1960 over the same ten years.
How the Keystone KSTAW12INV-HC compares
The room air conditioner class we track runs from $51 to $389 a year. At $126/yr, it runs about $27 a year above the class median of $99, and it is about $75 a year more than the cheapest room air conditioner to run at $51. Against the US federal standard model for its class at about $196/yr, the Keystone KSTAW12INV-HC uses 36% less energy.
What drives its running cost
At 12000 BTU/hr, the Keystone KSTAW12INV-HC is a mid-size room air conditioner for its class, which spans 5000 to 34100 BTU/hr with a median of 10100 BTU/hr, putting it squarely in the middle of the class on the size lever that drives most of the cost. 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 KSTAW12INV-HC cheap to run?
Its $126/yr running cost, rank #313 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 KSTAW12INV-HC cost per month?
About $10.47 a month, which is the $126 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: 677 kWh from ENERGY STAR times the US average of $0.1856/kWh comes to about $126 a year. It covers electricity only, not the purchase price, water, or installation.
How efficient is the Keystone KSTAW12INV-HC for its size?
8th 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
| Rank | Model | Cost/yr |
|---|---|---|
| 312 | Tcl W14WC72-B14000 BTU/hr | $122 |
| 311 | Tcl W14WC7214000 BTU/hr | $122 |
| 310 | Tcl T14WV9SB14000 BTU/hr | $122 |
| 309 | Tcl T14WV9S14000 BTU/hr | $122 |
| 308 | Midea MWEUWA-14CRFN8-BCP014000 BTU/hr | $122 |
Source
ES_1055302_KSTAW12INV-HC_040720230733943_5670808View certified room air conditioner listingsENERGY STAR data as of July 2026Keystone and KSTAW12INV-HC 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.