Where can I find estimates for BTU , EER or COP of very old air conditioners? (from the 1990's)
The 10 SEER minimum was right around that time period so it would most likely be 8 or 10 SEER. Window air conditioners at that time were listed as appliances and were not subject to testing so manufacturers could make up any numbers they wanted to. The BTU ratings would be all over the place in those days. You could take two 12000 btu air conditioners and one would cool considerably better than the other. And since EER is basically BTU/Watts then a change in the BTU would be a change in the EER. Air conditioners also loose their efficiency over time since it is a function of how it can transfer heat and the heat exchanging coils will delaminate over time. Not usually fully but there will be oxidation forming between the copper tubes and the aluminum fins.