Drupal 7 Features 2 screen

Until we can override the enabled module/theme/library list dynamically in Drupal 8 via configuration, we can bundle up our environment-specific development modules and Strongarm variables in a feature and enable the feature on a per-environment basis in settings.php (or even better, local.settings.php) via a project called Environment Modules. For example, one could create a feature for the development environment, enable the devel module, and set environment-specific Strongarm variables such as those that leave Drupal core caching disabled or environment-specific settings for Domain Access domains. Additionally, whenever refreshing the development, integration or staging environment databases from the production database as part of a release cycle, doing a simple Features revert reenables the correct environment-specific modules and sets the right environment-specific variables.

As the Environment Modules project states, $conf['environment_modules'] should not be set on your production site in its settings.php, however the module itself can still remain enabled on production without a performance hit — it just doesn’t do anything in that particular environment.