Google’s head of search spam, Matt Cutts, announced at SMX Advanced that Google is likely going to roll out a version of the site speed ranking factor for mobile sites. Back in 2010, Google said site speed is a ranking factor. Google’s Matt Cutts said expect something similar to come to mobile search soon. Google announced demotion factors for mobile sites, but they did not announce site speed as one of those demotion factors. That is because that feature is not yet live but it is coming soon, and Matt wants webmasters and SEOs to prepare. Matt mentioned a tool at Google I/O to monitor the speed of mobile websites. Outlier sites that load really slowly will see a demotion of the search results. I assume mobile sites have to be even faster than the outlier for the deskop outlier speed number.
Until now, Site speed was not affecting Google Ranking until and unless it has a good content and the users who visit the page are staying there because of the content. Google is preparing it, for this new roll and soon we would be seeing the same.