what is Siri consuming? is Wifi enough? or 3g celluar data is involved while Siri searches online? So I am concerned if I can save data usage(I have only 200M per month on my account..) by using Siri at home(with a wifi connection)??
You will save on data usage if you only use Siri at home with a wifi connection. Siri sends the raw audio of your talking to its servers, so the data usage will be comparable to using VoIP. Although that's only if you talk constantly to Siri (which I'm actually seeing some people at work doing these days).