All of your sites pages should load within three seconds. After five seconds the number of people still waiting for your page to load is about half of those who started. As your page takes longer to load, Google lowers your rank so it can serve visitors results that they’ll use.
A Lot of people discard this element of Technical SEO and a lot of people aren’t going to rank for the keywords they want. Optimize your page content and server hardware to ensure pages are visible with in three seconds.
Test the top results for the keyword you’re hoping to rank and I can pretty much guarantee it loaded in under 3 seconds. The top result for Barack Obama was his Wikipedia page. It loads in 2.8 seconds according to GTmetrix. The top result for Ultimate SEO is SEO Ultimate Plus and they load in 3.9 seconds. Our site loads in 3.4 seconds.
Page speed is one of 200 factors that go into Google ranking. Its one of the easiest to change though.