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.
What you can do now
Whether you have a Windows-based system or a Mac laptop, there's a lot you can do right now to make its energy use more efficient and get more life out of its battery. The tips and tricks that follow may not work for every system, but even if you choose one or two, you can make your notebook more efficient.
1. Slow down your CPU
The processor is a great place to save a few watts.
If you're using an older Windows-based system, start with your Control Panel Power Options page, go to the Change advanced power settings section and click on Processor to adjust its maximum processor state. I aim for a balance between performance and power use, and typically set the processor's maximum power use to 95%.
If your machine is recent enough to have a Haswell processor -- and therefore has Intel's Turbo Boost overclocking -- anything less than 100% prevents the CPU from raising its clock speed (and power use) when the computing load increases. In other words, if you want to keep your battery use down, lowering the maximum processor state will add even more power efficiency, even if it takes a moment or two longer to complete some tasks.
Unfortunately, at the moment, there's no easy way to easily disable or control Turbo Boost in a MacBook. Your best bet is an open-source XCode-based command-line tool called Turbo Boost Disabler for Mac OS X.
While you can't easily control Turbo Boost in a MacBook, the Intel Power Gadget can keep you informed.
If you're just interested in how much power your processor is using (including its clock speed and core temperature), you can use the Intel Power Gadget.
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