Thanks for posting in the forums! That's a great question. When streaming in your own network, the Slingbox does use Internet bandwidth but not nearly as much as it would use if you were connecting from a remote location.
The reason that is uses the Internet in your home is because the Slingbox first goes from your network to our servers, in order for it to have the functions it does.
Feel free to reply if you have any other questions!
Have a great day!
The Sling Moderation Team