It is explained like this in the thread. > if you have a large compressor, you pay more for it with every revolution the trick is to figure the maximum BTUs o

It is explained like this in the thread. > if you have a large compressor, you pay more for it with every revolution the trick is to figure the maximum BTUs or watts you will need, and design a little bit smaller. Plan to use a supplimental energy source to fill in during extreme conditions. Worth noting the AC_Hacker paid $25 for the AC he used for this.