Why are laptop battery life estimates so wrong?

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New laptops promise anywhere between 15 and 24 hours of battery life – truth is, you’d be lucky to get just 10. So, why are manufacturers’ estimates so far off?

Put simply, the advertised laptop battery life estimate is based off unrealistic benchmarks that yield the highest possible number. They are not false, but they don’t represent how most of us use our laptop on a day-to-day basis.

Let’s dive into this issue in a little more detail.

All laptop manufacturers do it

Let’s say one manufacturer decided to advertise a more realistic 8-hour battery life. Sat next to a laptop that promises 15 hours or more, their product will most likely be overlooked. To sell their laptops, manufacturers have to be competitive. And that’s why you’ll find overly optimistic battery life estimates advertised on almost every laptop computer on the market.

The question, then, is this: how do all laptop manufacturers get away with it?

Well, they aren’t lying. The over-the-top estimates do come from a real benchmark, and if you look closely at the specs, and you’ll spot some telling weasel words.

“Up to” 24 hours

Examine laptop packaging and online descriptions, and you’ll see two crucial words before the battery life estimate: up to. You’ll get “up to” 16 hours, or “up to” 24 hours. Just check out the example above, which was screenshotted from Microsoft’s Australian online store.

The estimate they give is the maximum number of hours anyone could possibly squeeze out of the device under perfect circumstances – not under regular use.

You’re probably familiar with these weasel words – they pop up in all sorts of advertising. For example, your internet service provider may offer “up to” 50Mbps. Chances are, you’ll only get 30Mbps or so because, in the real world, conditions aren’t perfect.

The video playback benchmark

The numbers manufacturers advertise are not pulled out of thin air. Here’s how the testing works.

Manufacturers open up a brand-new, fully-charged laptop and start playing a video. They leave the video playing until the laptop dies. There are no other processes going on in the background, and they might reduce brightness levels and other features to maximise battery life, too.

This is no secret. It’s hidden in the fine print that most of us never take the time to read.

Video playback uses less power

Have you ever sat down and watched 17 hours straight of video on your laptop, without doing anything else? We didn’t think so. The video playback benchmark doesn’t represent regular use.

Manufacturers aren’t too fussed about this, because video playback uses significantly less power than other tasks.

Newer laptops use a special kind of hardware-accelerated video decoding. Hardware in the graphics processor quickly and efficiently decodes video using the smallest amount of power possible. This keeps CPU usage down, which, in turn, drains far less energy.

This process kicks into gear almost anytime you watch a video – even if it’s in an app or on a website. It’s a great battery-saving feature, but it means watching video will use less battery power than browsing the web or writing a word document.

Look for independent reviews

You don’t have to rely on manufacturer benchmarks. There are a ton of independent reviewers out there, too. These reviewers use more realistic benchmarks to test battery life, such as web browsing, which is what most of us do on our laptops.

Anandtech is one website to check out. A quick Google search, and you’re sure to find a few more.

Remember, no battery estimate will be perfect

Even honest, independent reviews of laptop battery life won’t be perfect. There are just too many variables involved, and nobody uses their computer quite like you do.

So, take these estimates with a grain of salt. Most modern laptops have enough battery life to accommodate for travel, meetings, out-of-office work, school, and, importantly, watching movies in bed. There are other, potentially more significant, specs to consider when buying a new PC.