Searching for ET in a Green Way (best practice wanted)

As a cloud computing contributor for over 12 years since joining the SETI@home (search for extraterrestrial intelligence at home) in Y2K, the carbon footprint has not been seriously considered. The picture below showed the relationship of the thermal sensor readings and the % of CPU time consumed by SETI client on my home server, which is a 12-year old Pentium III 500 MHz laptop, in six CPU usage threshold profiles ranging from 100%, 80%, 60%, 40%, 20% and finally to 0%.  In summer the temperature can go as high as 75°C (167°F) running SETI in full throttle, while as low as 44°C (111°F) when idling.  Given the global warming issue, the soaring electricity fee,  and being a not-so-serious contributor, I think 40% might be a good choice for my home server.  If you have a better equation (in scientific way) for best practice please let me know. ;)