Google has announced that sites who add a SSL certificate will get a minor ranking boost. Security for Google is a top priority. Over the past few months they have been running tests taking into account whether a site use secure, encrypted connections as a signal in their search ranking algorithms. The results they have seen have been positive, so they decided to start using HTTPS as a ranking signal.
“Over time, we may decide to strengthen it, because we’d like to encourage all website owners to switch from HTTP to HTTPS to keep everyone safe on the web.”
So while these changes are currently only small, it is worth looking at getting your site switched over to be secure.