OSX Mavericks introduced a few new battery-saving features: timer coalescing, App Nap and Safari Power Saver. On my early 2011 MacBook Pro, I’ve seen a legitimate 15-20% increase in overall battery life since upgrading to Mavericks.
However, I also noticed Time Machine was asking for a full backup almost once a week. This is frustrating because I push my backups over Wi-Fi, and a full backup (more than 100GiB) takes hours. That, and I don’t want to lose my backup history every week.
I can’t confirm it, but it looks like Mavericks changed a setting in Time Machine, no doubt to increase its reputation as truly power-saving. In Time Machine preferences, I found the option Back up while on battery power unchecked.
Since my MacBook is almost always on battery power, it almost never pushed incremental backups. When Time Machine knows it hasn’t had successful incremental backups for a while, it decides that the only sensible thing to do is start over.
Since re-checking this box, I’ve had successful incrementals, and no requests for new full backups.