At the Search Marketing Summit in Sydney today, Gary Illyes from Google has been reported as saying that page speed ranking factors for mobile, will be mobile specific, in the upcoming months.
Currently, Google doesn't separate out many desktop signals for mobile rankings even when it makes sense. Such as how fast your page loads is based on your desktop site page load, not your mobile site page load. Same with accordions and hidden content and other factors.
But as we reported over a year ago, Google is looking to add mobile specific page speed to the mobile friendly ranking algorithm. Jennifer Slegg reported that Gary Illyes from Google said it is now "months" away. But later on, on Twitter Gary said it is still just in the "planning phases," so I am not sure if "months" is a realistic number here? Gary has given general timelines in the past and ended up not happening, but either way, I am glad they are "planning" it now.
Gary Illyes @methode@jenstar as I said, we're still in the planning phase so I can't give you a concrete answer.
Gary also was asked how fast does the page need to be? He said aim for the highest speed you can. Green is great he said but like desktop, I doubt it will be that important. If your site is incredibly slow, then yea, see a negative impact but if you are a tiny fraction faster than your competitor, I don't know if that will make much of an impact.