An interesting article in Slate by Jacob Leibenluft the other day asks a simple question:
Do you save more energy keeping your laptop plugged in during use, or should you use your charger only after the battery runs out of juice?
It's a complicated question, with even more complicated answers, since different manufacturers give slightly different answers: Lenovo and Dell reportedly say your battery should be fine if your computer stays plugged in; HP says you should remove the battery if you are running on AC power for weeks at a time; Apple suggests you should unplug and run off the battery every once in a while.
So who's right?
Assuming you use the same energy plugged in and not, you're probably better off staying plugged in, because energy is lost in the process of charging the battery, storing the electricity, and then powering the computer from the battery, according to Leibenluft.
A report (.pdf) prepared by the Natural Resources Defense Council five years ago estimated that running a laptop from AC power is about 20 percent more energy-efficient than doing it off a battery.
But that was five years ago, ages in tech time. Leibenluft reports: "Even if battery charging systems have improved since then, common sense suggests that using AC power requires less energy."
The article takes the green angle, noting that just by using a laptop (and not a desktop), you're already saving money, since laptops are far more efficient and require less energy to manufacture than their boxy counterparts.
If you contend that keeping a laptop plugged in damages the life of the battery, it's an even tougher call: Batteries require an awful lot of energy to manufacture, and there's an environmental cost to recycling a spent one, so what's worse in the long run?
But that's the global view. What about the energy bill you pay for at the end of each month?
The final tally can also be affected by this caveat: most laptops are set up to use less energy when they aren't plugged in, since battery life is at a premium, so as soon as they start receiving AC power, they're more inclined to kick it up a notch, performance-wise (brighter screen and so forth). So if you've never touched your laptop's power settings before, chances are it uses more energy when it's plugged into the wall.
So who's right in this debate? It's still unclear, and the vampire suck of your computer's power adapter only makes matters worse.
Do you plug in or unplug when you use your laptop? Tell us in TalkBack.