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).
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