According to Netflix website, streaming video in "best" quality can use 3GB per hour.
https://help.netflix.com/en/node/87
Looks like you can dial down the quality of the video to save bandwidth.
From that link -
Watching 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 that have a monthly bandwidth or data cap on their Internet service. Below, you'll find a couple of ways to reduce the amount of data Netflix uses, without having to resort to drastic measures (like actually watching less Netflix).
Adjust your data usage settings
Adjusting the data usage settings for your account is the easiest way to reduce the amount of bandwidth used while watching Netflix. There are 4 data usage settings to choose from, each estimate below is per stream:
Low (0.3 GB per hour)
Medium (SD: 0.7 GB per hour)
High (best video quality, up to 3 GB per hour for HD, 7 GB per hour for Ultra HD)
Auto (adjusts automatically to deliver the highest possible quality, based on your current internet connection speed)
To select a setting that works best for your Internet plan, navigate to Your Account page and click Playback settings in the Your Profile section. It can take up to 8 hours for these changes to take affect. Restricting data usage may affect video quality while watching Netflix.
>>
To bad that can't be adjusted for each device. I'd use high quality at home (TV) and low to medium on the phone/iPads.
Here is a quick rundown of how the usage posted -
01/09/2015 05:00PM - 419.63 MB
01/09/2015 04:49PM - 515.00 MB
01/09/2015 04:38PM - 534.07 MB
01/09/2015 04:26PM - 457.78 MB
01/09/2015 04:15PM - 934.63 MB
01/09/2015 04:03PM - 1182.59 MB
01/09/2015 03:52PM - 1182.59 MB
01/09/2015 03:40PM - 1068.14 MB