I am creating a 20-page site that will go on shared hosting. Each page will be about 20 KB (including HTML, CSS, and images common to all pages). To avoid manually adding navigation elements to each page, I am considering using a CMS. However, I am concerned that on a busy server, using a CMS would make the site load more slowly.
In a shared hosting environment where PHP is run as a CGI binary, how much does a CMS (WordPress, Drupal, etc.) generally affect page load time, compared to both "plain HTML" static sites and those using PHP as merely a templating language?