How much space is available on the online account of the Xperia Backup & restore application?

The online account of the Xperia™ Backup & restore application offers 500 MB of storage space for each user. This is usually enough, but if many applications that produce a lot of data are backed up on the account, you may run out of online storage space. If so, remove apps that you don't use from your device, or choose to back up apps on a memory card or computer instead of to your online account. 

Every time you perform a a new backup to the Xperia™ Backup & restore application, the previous backup will be overwritten.