renderTemplate in a plugin for front end request using front end template
Craft will only serve templates from craft/templates/ by default if it’s a front-end site request.

To explicitly tell Craft to serve templates from there, you can use PathService::setTemplatesPath():

$path = craft()-&gt;path-&gt;getSiteTemplatesPath();
craft()-&gt;path-&gt;setTemplatesPath($path);

$this-&gt;renderTemplate('path/to/template', $variables);