For the sake of optimising my MBA was checking with Activity Monitor the most active processes. Safari have the lion's share but the nimble f.lux is close to the top. Surprise. On average above Notes and below Text Expander. Those two are interactive and frequently used apps. F.lux sits on the background adjusting color once in a while. Maybe is consuming a little bit too much for the (useful) service provided?
May be possible in the future to add a preference to change refresh frequency? Thanks.
I have seen some new issues in 10.11 that are making us think the system profile has changed frequently (which is 100x more expensive than our normal work in the background). We will do a fix soon.