It's worth noting that Zen Cart itself doesn't require anything near 1GB. Zen Cart itself is very small.
The things that could blow out your storage space are:
- your images
- logging of emails sent -- setting in your admin, and an Email Archive Viewer/Pruner plugin available in the Plugins library to clean those up
- logging of PHP errors in your /logs/ (or formerly /cache/) folder (or in older ZC versions, also the /includes/modules/payment/paypal/logs/ folder)
- files added by plugins
- cached items added by plugins (such as various tools like CEON mapping, Image Handler, XML sitemap, and more)