Based on what I've read, I've never measured how much is streamed, I believe downloading v streaming is the same. At least I've never seen anything concrete to the contrary. They could change the file size base on the device, phone vs tablet vs television, I suppose, but not sure. I've read about the new HEVC codec (h.265) that they will be using for streaming 4k, and it is supposed to not only offer better compression for higher resolution at the same bandwidth, but also offer scalable coding extensions which will allow the one file to be served up at the resolution best needed by the device. Not sure if it's in use yet though.