[operagost]

I can get a 1 ton window unit for around $249 at 9.8 EER or $299 at 10.8 EER. How can I determine when I will get my ROI for the difference in EER of the more expensive unit?

 

[beenthere]

EER BTUs per watt. So the higher efficiency unit will get you 1 more BTU per watt used.

So per hour of cooling run time, it will use 113.37 watts less electric. Which comes out to saving 1 KW for every 8.82 hours of cooling run time.

So if you know how many hours it will run for the season, divide by 8.82 and that will be KWs saved, just multiply by your electric rate then to find money saved.