According to this article on site speed and ranking by Moz Google has indicated that site speed is one signal that is important to ranking. However, when we at Ducktoes SEO of Calgary tested this, we didn't find that increasing the page speed of the site increased its ranking.
What We Did
We took two of our SEO clients websites that used a highly customized Divi theme for Wordpress which made them slow to download from the web. We streamlined their code to make them download much faster. We waited for Google to index the faster loading sites. No increase in ranking for either site. We waited a month. No increase in ranking.
One of the sites we made a lot faster. Their site speed went from 40 to 89. It took about 60 hours for my web developer to streamline the code so it wasn't cheap to speed it up. However, the increased site speed didn't help the ranking.