Have a window AC unit that's from 2001, here are the specs:
- Manufacturer: Kenmore
- VOLTS: 115
- Cooling BTU/HR: 12500
- Cooling AMPS: 11.6
- Cooling WATTS: 1275
- Cooling EER: 9.8
The average electricity rate is 11.04¢/kWh.
As for the hours of use per day, currently varies anywhere from 12 to 24 hours of use per day, so I'm not sure how to deal with that; maybe the easiest way is to just do two estimates, one for 12 hours of use, and another for 24 hours of use.
User Manual is here.
Very possible that I've left out some information, but even with the above information, I still haven't been able to figure out how to even do a rough comparison.
Best Answer
The EER (energy efficiency ratio) is a lovely mashup of units (BTU/h)/Watts (ie, 12500/1275 in the questioned case) that will tell you (part of) what you need to know. The rest is up to how much you run it.
It uses 1.275 KWh/h (1275 watts) and that costs you 14.07 cents/hr at 11.04 cents/KWh
Compare to whatever you think you might replace it with - you'd want a higher EER than 9.8, or you could just look at 12500 BTU models and compare watts directly. Less watts costs you less per hour to run - if they are all cooling by the same amount (12500 BTU/hr) then the lowest watts is the most efficient and should have the highest EER as well.
A low-effort search (ie you might find better) shows a current EER of 11.3 on one similar new unit. If exactly equivalent in BTU/h that would be 1106 watts, or 1.106 KWh/h, or 12.21 cents per hour, or a savings of slightly less than 2 cents per operating hour.
If willing to step away from the window-unit format you may be able to get much better EER in a mini-split type system, but it will likely cost more up front.