The BBC iPlayer service delivers up to 100 gigabits of data every second, which apparently works out at a total of around 7 petabytes of data transfer a month. That sounds a lot but it is nowhere near the amount of data received from broadcast networks. So how will such streaming services scale if people increasingly consume video on demand?

Anthony Rose, who among other things heads up the BBC iPlayer project as Controller of the Vision and Online Media Group at the BBC, revealed some interesting statistics in a recent interview with CNET.

“I think that at the moment, just for streaming, iPlayer uses about 60Gbps of bandwidth (that’s about 7.5GB downloaded every second) in an evening peak,” he said. “I think about 15Gbps for downloads, and about 1.5Gbps for iPhone. So overall on a particular peak day we may hit 100Gbps (about 12.5 gigabytes per second) although typically it’ll be somewhat less than that. That turns out to be up to 7PB of data transfer a month.”

A petabyte is a equivalent to a thousand terabytes or a million gigabytes of data. To put it in perspective, the AT&T network delivers around 16 petabytes of data on an average day.

Streaming 60Gbps is equivalent to delivering the data on a typical DVD every second. Assuming an average of 500Kbps per stream, it works out at around 120,000 simultaneous streams at peak. The BBC iPlayer also offers higher quality streams at 1,500Kbps, so the actual number could be lower than that.

In comparison, a broadcast programme may be transmitted at up to 4Mps in standard definition, but can be received by an arbitrary number of viewers. The total amount of data transmitted is still less than a typical DVD.

A popular broadcast television programme like The Apprentice might be simultaneously viewed by around 8 million people across the United Kingdom. It turns out that they collectively receive more data than the entire BBC iPlayer currently delivers in a month.

Such is the efficiency of broadcasting and the comparative inefficiency of streaming on demand.

It seems clear that significant changes may be required in network infrastructure if services like the BBC iPlayer are to reach anything like the popularity of broadcast channels.