Bandwidth usage is one of the many pain points for cloud gaming services. When you are streaming games directly to your device, a large amount of bandwidth is needed to be used to provide you with the best experience.
One of the main factors to bandwidth usage in cloud gaming is the resolution and frame rate you are streaming in. Most streaming services offer 1080p/60FPS streams. Some offer 4k/60FPS, and even more are now offering a 720p/60FPS option to reduce overall bandwidth usage.
Google Stadia is no different. As seen by Bryant Chappel and Gem on Twitter, Stadia recently received an update that would allow you to select a "mobile data optimized" variation of 720p streaming, roughly cutting your hourly bandwidth usage by nearly 40%!
Utilizing this mobile optimized bandwidth setting will result in lower overall quality, and it is only suggested for use on smaller screens, as the quality loss will be less noticeable.
If you are interested in using this "mobile data optimized" variation of 720p streaming, all you need to do is head over to your Stadia Settings and then go to the Performance tab. Here, you can select the resolution that you would like to stream in.