Reviews indicate that the Duracell CopperTop is one of the most reliable alkaline batteries you can buy. Although its performance isn't significantly better than its competitors', it lasts longer than average, especially in low-drain devices. It also has a guaranteed shelf life of 10 years. The biggest problem with this battery is that, according to some owners, it's prone to leakage -- though it's unclear whether it's any more so than other brands.
A solid performer. Most reviews of alkaline batteries show there isn't all that much difference in performance between brands. In one professional test, for instance, all alkaline batteries are either good or very good at powering a flashlight, which draws relatively little current, and only fair at powering a high-drain digital camera. The Duracell's performance is above average for the group, but it doesn't particularly stand out. One plus of the CopperTop, however, is that its latest version includes DuraLock Power Preserve technology, which means it's guaranteed to last 10 years in storage.
Long lasting. The Duracell is above average, if not outstanding, when it comes to battery life. In the professional test mentioned above, it lasts longer than most of its competitors, though not nearly as long as lithium batteries like the Energizer Ultimate Lithium (Est. $6 for 4 AA). At Amazon.com, many owners praise the Duracell's reliability, saying it's much less likely to leak than cheap off-brand batteries. However, some Amazon reviews, and most of the reviews on Duracell's own site, complain that this once-reliable battery has become extremely leak-prone. Other alkaline batteries also have many complaints about leakage, so it's not clear whether Duracell is any worse than competing brands.
ConsumerReports.org's editors test 13 brands of alkaline batteries and two lithium batteries, using both high-drain devices (cameras) and low-drain ones (flashlights). Lithium batteries consistently outperform alkalines like the Duracell CopperTop, but some alkalines last longer than others. About half the alkaline batteries in the test earn a recommendation.
Review: Batteries, Editors of ConsumerReports.org, Not Dated
A team of students at Worcester Polytechnic Institute tests a variety of AA batteries, measuring each one's voltage before and after 19 straight hours of use. Testers find no significant difference in performance between name-brand alkaline batteries, like the Duracell CopperTop, and cheap generics.
Review: Test Results That Will Change the Way You Buy Batteries Forever, Mitch Lipka, March 31, 2011
Allain tests the Duracell CopperTop against an Energizer battery and a cheap zinc-chloride battery from a dollar store. He uses each one to power a light bulb until it dies, measuring its current and voltage throughout. The Duracell and Energizer perform almost identically, while the cheap battery dies much faster.
Review: Are Expensive Batteries Worth the Extra Cost?, Rhett Allain, Jan. 23, 2012
Duracell CopperTop AA battery earns an overall rating of 4.4 out of 5 stars from over 400 users at Amazon.com. Most say it's long-lasting and less prone to leakage than other brands, but some users complain that Duracells have become less reliable in recent years.
Review: Duracell Coppertop Alkaline Batteries with DuraLock, Contributors to Amazon.com, As of May 2014
The Duracell CopperTop receives an unimpressive overall rating of 1.7 out of 5 stars from 50-plus users on the manufacturer's website. Most of the reviewers -- many of whom say they used to be loyal Duracell users -- complain that in recent years, these batteries have become unreliable and leak-prone.
Review: Duracell CopperTop, Contributors to Duracell.com, As of May 2014