Here’s the deal, engineer types - I have to choose between precisely two models of wall-through air conditioner (more on why below). One model is 13,000 BTU with a 9.5 EER, and the other is 15,500 BTU with an 8.9 EER. The former is Energy Star qualified and the latter isn’t.
I’m honestly not sure if the 13,000 BTU model is enough - my current a/c is 12,400 BTU and it struggles, constantly (it wasn’t installed properly and probably suffered permanent damage as a result, but I’m not sure). So assuming that 13,000 is about what I need, am I better off getting a 13,000 BTU model that’s higher efficiency, but runs constantly, or a 15,500 model that’s lower efficiency, but won’t run as much?
As for why I have only two models to choose from - I live in a co-op building whose house rules prohibit window air conditioners. My apartment is located directly above the building’s entrance, so putting a big honking window a/c unit up would be just a weensy bit noticeable. And pissing off one’s co-op board is not a good idea. Ever. So I’m stuck with using the wall-through sleeve I own, which fits only Friedrich and Fedders models. From all reports, Friedrich are superior to Fedders, so that’s all I’m looking at. (Everyone has told me that I should only use models that fit the sleeve precisely - apparently, units that are smaller in size are a Bad Idea, although if that’s not the case I’d be interested to know.)
Further fun facts: it’s a studio apartment, about 450s.f. with kitchen (which I use). The floors above and below me are occupied. Standard 8’ ceilings. Virtually no ventilation - there are three windows in the front of the apartment, and that’s it. They face northeast. Air does not move.
Is your current A/C Energy Star? If not your electric utility might have a program that will pay part of the cost of an Energy Star replacement for it.
EER is cooling capacity/power used. A 13000 with EER 9.5 takes 1.368 kilowatts. If it runs 15 hrs/day that’s 20.5 kilowatt hours. The less efficient unit would use the same amount of power in 11.8 hours. So that is one gauge. In 15 hours the more efficient unit would remove 195000 Btu of heat while in 11.8 hrs the other would only remove 183000 Btu. It looks like the smaller more efficient unit removes more heat for the same eletrical cost than the bigger, less efficient one.
This estimate leaves out such things as power factor. The definition of EER is cooling capacity/watts used. I really don’t know whether that means actual watts or the more common loose use of “watts” to actually refer to volt-amperes.
Yes. In this case it looks like the more efficient and smaller unit will remove more heat from the room than will the bigger one for a given amount of electricity used.
I was afraid of that. In that case, just ignore all that stuff. It seems to me now on thinking it over that the only way the EER would be useful is that it be based on actual watts used and not on volt-amperes.
So just pretend I didn’t write that last paragraph.