Netflix streaming: how much bandwidth does it use?

The most believable numbers I've found are 1.5Mbps for SD, 3Mbps for DVD quality, 5Mbps for HD quality and 8+ for 1080 on PS3. I don't see Netflix offering official numbers, but playing with Speedtest.net and testing by adding bandwidth eaters like VPN connections until I saw the quality degrade.

For what it's worth, the company I work for was going to do a partnership with Netflix a little over a year ago (so these numbers represent that -- it could have changed since then). I helped produce our streaming video sites, so I was in contact with one of their techs. At the time, they were using multiple-bitrate WMVs. Basically, these are containers/streams that are served from Windows media servers that adapt based on your bandwidth. The high end (at the time) were 3Mb/s WMVs, with the lower side being in the 100's of kilobits per second (maybe ~700kb/s, but I honestly only distinctly remember the high side @ 3Mb/s). So, if you had enough bandwidth, they were 3Mb/s streams, but if you couldn't support that they would throttle down to one of the lower bitrates. All of this is to say that Netflix supports lower bandwidths, but the quality of the video is going to fluctuate accordingly. If you have a 3Mb or higher connection, you'll be able to watch everything at the best quality they offer. If your connecting is 1Mb, your video is going to be more compressed.