Drupal 7 - Query for existing user entry

<?php
    // instantiate the query using our extended query object
    $query = new EntityFieldQuery();

    // let our query know which node types we want
    $query->entityCondition('bundle', array('user'))
          ->entityCondition('entity_type', array('user'))
          ->fieldCondition('field__ser_name', 'value', $value);

    // execute the query
    $result = $query->execute();