Whether it happens with that key memo left unfinished, the last scene of a movie unwatched or an epic gaming battle interrupted, it's likely that, at one time or another, you've been left with a dead notebook battery at the worst possible moment. What can you do about it?
"Notebooks are not as efficient as they could be," says Robert Meyers, data center product manager for the Energy Star Program at the Environmental Protection Agency, "and they waste a lot of energy."
The payoff for being aware of how much power your system uses and how to control it can be huge -- because every watt saved can run the notebook that much longer. "The natural incentive is that greater efficiency translates directly into longer battery life," Meyer says.
In this article, I'll go through 11 ways you can cut down on your laptop's power usage. Some may be appropriate for your style of work and/or play, some not; but even if you follow one or two, it could give you those crucial extra operating minutes.
But first, it might be useful to look at which components are the most power thirsty in your device -- and how they are being improved.
What uses battery power?
While there's a lot of variation between an 11-in. Chromebook with an Intel Celeron processor and a 17-in. gaming laptop with an Intel Core i7 Extreme chip, each has a similar array of components that turn electricity into an interactive computing experience.
There are six components that are the major power users in a computing device. They are listed here roughly in order of power use, although that can vary based on the notebook itself. They have each been redesigned over the past decade for greater efficiency, but there's still work to be done.
The processor is a power hog, often using as much as half of the total power in a system. Smaller is better; as the size of the microscopic wires and electronic architecture within the chip shrinks with each generation, its power use declines.
A decade ago, the best Intel processors used the company's 90-nanometer (nm) production process, codenamed Dothan. Today, the company's Haswell chips have 22nm architecture -- less than one-quarter the size and roughly 100,000 times smaller than the width of a pencil point. Chips made with 14nm microarchitecture, a.k.a Broadwell, have been promised for later this year or in early 2015.
Meanwhile, current AMD processors are made using a 28nm process, including the new Karavi laptop CPUs, but the company's Project SkyBridge promises a series of new chips for mobile devices using a 20nm manufacturing process.
2. Graphics processors
Graphics processors are often integrated into a notebook's system, but can significantly drain a battery as well. For example, Intel Graphics 4000 and 5000 integrated video chips typically range in power use from about 15 watts for the HD 4200 at the entry level to upwards of 50 watts for the Iris Pro 5200.
AMD's Radeon graphics engines also vary in how much power they pull. For instance, the mid-range HD 6290 graphics chip consumes about 18 watts at peak use, while the more sophisticated HD 8650G chip uses upwards of 35 watts.
Plus, many high-end engineering and gaming notebooks also have discrete graphics chips with dedicated memory from Nvidia or AMD that can consume a lot of power when they're being used.
Displays have improved -- no doubt about it. The move in the late 2000s from CCFL backlighting to LED backlighting reduced a typical LCD's power drain by about 25%.
More recently, Panel Self-Refresh (PSR) technology can lower power use even further by stopping screen refresh if what's being displayed doesn't change. This can add as much as 20 minutes to a battery's run time, according to Ajay Gupta, director of commercial notebook products at HP. PSR is currently used on a limited number of devices, including the HP EliteBook Folio 1040 and the LG G2 smartphone.
In the long term, display power use could decrease by another 40% by using Organic Light Emitting Diode (OLED) screens that produce their own light and don't require backlighting. These screens are currently being used in phones like the Nokia Lumia Icon.
Traditional hard drives that use rotating magnetic discs are giving way to SSDs that store data on solid-state chips. Solid state storage still costs four to five times what a hard drive goes for, but uses a lot less power.
For instance, the 500GB Seagate Momentus Thin 2.5-in. mobile hard drive (starting at $50) uses 1.20 watts, while a 480GB Crucial SSD (about $236) consumes 0.28 watts, less than a quarter as much. And more lower-cost laptops -- including such lightweight models as the HP Chromebook 11 -- are shipping with SSDs.
According to Gupta, the next step is to stop making SSDs that mimic 2.5-inch hard drives in size and shape, and move to M.2 circuit board technology that puts all the components on a small circuit board, such as the one included in HP's EliteBook 840. This can reduce power use further, he says.
Every watt used inside a computer system turns into heat -- and so the system has to be cooled in order to keep running. The less power used, the less cooling is needed. As a result, current systems that use power more efficiently also use smaller fans that don't need to run as often (and so conserve power themselves).
6. AC adapter
The technology that turns a wall outlet's alternating current into the direct current that a notebook needs has made great strides: From being roughly 50% efficient 20 years ago to between 80% and 90% efficient today. Still, a lot of power is wasted, because for most computers the adapter still draws phantom current after the system's battery is fully charged.
Today, some adapters -- like that of the Lenovo ThinkPad X1 Carbon Touch -- are smart enough to shut themselves off when the battery is full. Hopefully, more are on their way.
According to HP's Gupta, a high-efficiency adapter could be made for a single voltage, like the 110 volts we use in the U.S., rather than switchable between 110- and 220 voltage for global use. Theoretically, it could hit 94% efficiency, he says.