Siri was introduced with Apple's iOS 5 and iPhone 4S as a new intelligent assistant feature that performs certain tasks and retrieves information via natural voice commands. Since the service works by communicating with Apple's servers, the question has come up of just how much data does Siri consume and how that may affect folks on limited data plans. Well, tests have been done and thankfully Siri's on a lean diet.
ArsTechnica conducted a total of 11 tests split between two groups of queries. The first being local queries needing only data to interpret the spoken input such as dictation and setting up reminders. The second group involved queries to return results from the internet, such as through Wolfram Alpha or Google. The local tasks used an average of 36.7KB per query while the internet queries averaged about 94.72KB. Tests were also done on text dictations for two short e-mails and two text messages, which yielded an average of 72.5KB. The longer the message, the more data was used.
Overall, the average data use per query was found to be 63KB. This means that if someone were to perform the 11 queries using Siri every day on a 3G network, it would consume about 20MB of data per month. This isn't too bad and certainly won't put a huge dent on limited data plans, especially if you also take advantage of WiFi connections.