FWIW- I have been using some iPhone apps, and especially Strava just riding around town commuting. I don't honestly notice being any more drain on my phone than not using it (although I am sure that it is). However, at the same time since it stays in sync with my Apple Watch, which I love, Strava will kill my watch in a few hours. Really don't know why, if I don't use Strava my watch will go all day with little drain from other use.

Doesn't answer your computer question but I find it odd that Strava drains my watch that much.