We’ve suspected for some time now that site speed was a factor in the Google algorithm and today Google has sort of confirmed it. The only strange thing is that they have confirmed it is currently only live on Google.com.
While site speed is a new signal, it doesn’t carry as much weight as the relevance of a page. Currently, fewer than 1% of search queries are affected by the site speed signal in our implementation and the signal for site speed only applies for visitors searching in English on Google.com at this point. We launched this change a few weeks back after rigorous testing. If you haven’t seen much change to your site rankings, then this site speed change possibly did not impact your site.
This is interesting because a lot of the rumours are that this algorithm is live in the UK already but it seems the rumours might be wrong if you believe the wording of the post above.