Using your own PC in your home is much more energy efficient than servers and SAN/NAS in a hosted data centre. I can tell you from my current data centre experience that the blade/standalone servers and storage options take more power today than they did 3 years ago.

An option could be Mozy. It is a backup services with inexpensive rates and the client is pretty fast. You can selectively "restore" files, which essentially means you use a web interface to tell mozy what you want to restore and it will provide you with a zip of the requested files within minutes. It works quite well.

If you really want to be green, install on of these at home. ^