https://blog.gongquiz.com/2022/09/18/%ec%84%b1%eb%8a%a5%ea%b3%84%ec%88%98coefficient-of-performance%ea%b0%80-2-5%ec%9d%b8-%eb%83%89%eb%8f%99%ea%b8%b0%ea%b0%80-%ec%9e%88%eb%8b%a4-1-%ec%97%90%eb%84%88%ec%a7%80%ea%b4%80%eb%a6%ac/