Walt Mossberg

Power Testing: Can Two New Laptops Really Last All Day?

Most consumers pay little or no attention to the processors and other chips that power their computers, and rightly so. In recent years, changes to the design of these chips haven’t made major, noticeable differences in everyday computing tasks.

But this month, chip giant Intel introduced a new generation of processors and chips that it claims can dramatically improve something important to almost all users of light laptops: Battery life. In fact, it claims these chips, called the 4th Generation Core processors, can boost battery life by 50 percent while actually improving graphics performance. Intel says the new chips are the first it has designed specifically for the slim, light laptops Windows PC makers call Ultrabooks and Apple calls its MacBook Air line.


The Sony Vaio’s optional second battery clips to the bottom of the laptop, roughly doubles its battery life and boosts its weight to about 3 pounds.

These new processors, code-named “Haswell” before the release, have been eagerly awaited for months in an industry that has seen laptop sales suffer at the hands of tablets, partly because tablets typically boast much longer battery life. They have now begun to appear in some computers and this week I tested just the battery life of two new models equipped with these new chips. I focused on battery life since that is a huge factor for many users and Intel says the new chips provide its biggest battery-life gain ever.

For my tests, I chose the latest MacBook Air, introduced last week. The Air is the leading slim and light laptop in the U.S. According to research firm NPD, it outsold all Windows Ultrabooks combined in U.S. retail sales for the first four months of this year. I also took a look at an entirely new Windows Ultrabook, the Sony Vaio Pro 13, a handsome, even lighter laptop with a touchscreen to accommodate Microsoft’s touch-centric Windows 8 operating system.

In my tests, I was able to largely confirm Intel’s battery-life claims. This was especially true of the 13-inch MacBook Air I evaluated, whose battery life in my test jumped 65 percent from my last test of the machine, even though it hasn’t been significantly redesigned, except for the inclusion of the new Intel chips, faster Wi-Fi and solid-state storage and a slightly more potent battery. It has become a computer capable of all-day use when performing typical tasks, even though its dimensions and 3-pound weight are unchanged.

Because the 13-inch Sony is new, I couldn’t compare it with a prior test, but my results were generally in line with Sony’s claims. Out of the box, the 2.34-pound Sony delivers significantly less battery life than the Air, but with an optional second battery that clips to the underside of the machine, its battery life roughly doubles, while its weight grows to be about the same as that of the Air.

In addition to their impressive battery life, both computers equipped with the midrange i5 model of Intel’s line offered the speedy performance Intel promises and resumed from sleep almost instantaneously.

Their major downside is price. Although Apple cut the price of the upgraded 13-inch Air by $100, it still starts at $1,099 for a configuration with 4 gigabytes of memory and 128 gigabytes of solid-state storage. The 13-inch Sony, with the same memory and storage, is $1,250, and its optional second battery brings the price to $1,400.

These prices are much higher than the $600 to $800 Windows buyers have traditionally spent on a well-equipped laptop, but as the new Intel processors spread throughout the industry, there are likely to be less expensive models.

Without getting into the technical details of chip design, Intel explains it achieved the gains by making numerous tweaks to the power demands of its chips in both their “active states,” when the user is performing a task, and the frequent “idle state” when, however briefly, the demands on the chips drop dramatically. In addition, Intel has squeezed all the components onto a single piece of silicon, reducing the power needed for them to interact.

Apple, which unlike Sony controls its own operating system, said it also made many tiny software tweaks that reduced power usage without sacrificing performance. For instance, it was able to cut the power needed to play a video in iTunes, yet I noticed no degradation in the quality or playback smoothness of the same video played on the previous and new models.

For these tests, I used the same tough laptop battery test I’ve used for years. I disable all power-saving features, crank the screen brightness to 100 percent, leave on the Wi-Fi to collect email in the background and play an endless loop of music until the computer loses power and shuts off.

For the new 13-inch MacBook Air, Apple claims battery life of up to 12 hours. In my tests, the Air lasted an amazing 10 hours and 14 minutes, the longest any single-battery laptop I’ve reviewed has ever gone and about what an iPad gets. In more normal use, with power-saving turned on and the screen at 75 percent brightness, I estimate you could get well over 11 hours, nearing the company’s 12-hour boast. That compares with the last MacBook Air test I performed, which yielded a result of 6 hours and 13 minutes, and which I estimated could meet Apple’s claim at the time of 7 hours of battery life.

Sony claims 6½ hours of battery life out of the box for the 13-inch Vaio Pro and in my test it lasted 5 hours and 56 minutes. I estimate you could meet or even exceed Sony’s claim in normal use.

In a second test with the second $150 battery attached, the Sony lasted 11 hours and 52 minutes, compared with Sony’s claim of up to 13 hours. In normal use, I estimate you could approach that 13-hour mark.

Bottom line: Intel has pulled off a major gain in battery life with its new 4th-Generation processor, and I recommend you look for one with these new chips if you’re shopping for a light, thin, mobile laptop.

Email Walt at mossberg@wsj.com.

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