Streaming video in HD from most any service burns about 3 gigs an hour. Set your netflix account to low res and it burns about 0.3 gigs an hour. It is a huge difference, and is why we have 2 netflix accounts. One for the house is HD, and another account set to low res for mobile use. Other streaming services may not have this option.
From Netflix
Watching movies or TV shows on Netflix uses about 1 GB of data per hour for each stream of standard definition video, and up to 3 GB per hour for each stream of HD video. This can create headaches for Netflix members who have a monthly bandwidth or data cap on their Internet service.
Here for instructions on controlling netflix data use:
https://help.netflix.com/en/node/87
