Apple made some big promises on how well iOS 9 will improve your iPhone’s battery life — but did it deliver? Wired has been running some tests on iOS 9’s Low Power Mode and has found that Apple’s newest iPhone software seems to deliver the goods as long as you have Low Power Mode enabled.

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Early reviews of iOS 9 claimed that Apple had fulfilled its vows to improve battery life, although Wired’s piece is the first that tries to quantify this into actual numbers rather than general impressions. Overall, Wired found Low Power Mode consumed between 70% to 80% of regular battery power, although this performance depends on several different variables, as the publication acknowledges.

All the same, Wired finds that the battery power improvements are significant enough so that uses will notice a positive difference if they find themselves running low on juice.

“If the Low Power mode uses 70 percent of the power in standard mode, the battery should last 1.43 times as long,” the publication writes. “A 14 hour battery life would be 20 hours. That’s not too bad. I can live with a 20-hour battery life. Of course, the iPhone only suggests you turn on Low Power mode when you get to 20 percent battery life. In that case, the extra time is about an hour. Again, not too bad. Every little bit helps.”

Read the entire analysis of iOS 9’s battery-saving capabilities by clicking here.

Prior to joining BGR as News Editor, Brad Reed spent five years covering the wireless industry for Network World. His first smartphone was a BlackBerry but he has since become a loyal Android user.