Google is starting to use HTTPS as a ranking signal. From their webmaster blog:
“For now it’s only a very lightweight signal — affecting fewer than 1% of global queries, and carrying less weight than other signals such as high-quality content — while we give webmasters time to switch to HTTPS. But 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.”
Source: http://googlewebmastercentral.blogspot.com/2014/08/https-as-ranking-signal.html
Google adds HTTPS as an SEO ranking signal