The discussion focuses on calculating the coefficient of performance (COP) for a heat pump using only outdoor and indoor temperatures. An ideal Carnot engine model is suggested for maximum efficiency, with equations available in textbooks for both heating and cooling scenarios. To find the COP, one must convert temperatures from Celsius to Kelvin and understand that COP is a unit-less ratio of heat output to work input. The conversation emphasizes that the COP can be derived from the relationship between heat transfer and temperature, specifically using the formula Qhot/Thot = Qcold/Tcold. Ultimately, the key takeaway is that the COP is calculated as a ratio, not in Joules, and requires proper temperature conversion.