This is why your laptop battery dies fast

A simple change can help your laptop die less often.

Quick, what is the biggest drain on your laptop's battery?
If you answered "the display," you're right -- for the most part.
The single biggest occupier of battery resources, day in and day out, is your laptop's display. More specifically, it's the that energy goes into powering the backlight that illuminates the pixels on your laptop's display.
The obvious move to extend battery life is then to lower your display's brightness. On either a Windows 10 laptop or an Apple MacBook, you can usually do this on the keyboard, but there are a couple other settings to change that will help automate the process.

Change your display settings

Managing display brightness on Mac OS X

Open System Preferences and click Display. On the Display tab, you'll see a slider for Brightness. Lower it to a point between super bright and depressingly dull. Not only will a display set at a lower brightness aid your battery life, but it will also be easier on your eyes unless you are sitting in direct sunlight and need brightness at its max in order to see text and images.

Below the slider is a check box for Automatically adjust brightness, which may or may not help extend the life of your battery. If you use your laptop primarily in a brightly lit office or sunny breakfast nook, then keep this setting off so OS X isn't bumping up screen brightness to compensate for your bright environment. You're better off lowering the display brightness manually. Of course, the opposite is also true. If you often work into the wee hours at night in a darkened room or keep your office light low, check the box and let OS X lower the brightness in such settings.

Screenshot by Matt Elliott/CNET

There is another display-related setting on the Energy Saver area of System Preferences. Check the box for Slightly dim the display while on battery power.
Keeping your display running while your laptop sits unattended is a needless waste of battery resources. On the Energy Saver page, you can set times for Computer Sleep and Display Sleep, both of which spring into action if your MacBook sits idle for a period of time. Set as short a time as you're comfortable with for the Battery tab; it's less important for the Power Adapter tab.

Windows 10

First off, if you are concerned about your Windows 10 laptop's battery life, head to Control Panel > Hardware and Sound > Power Options and make sure you choose a Balanced or Power Saver plan. Use the High performance plan only when you need a boost for gaming or high-end graphics apps.
With Windows 10, there are additional power and display settings from the Settings button on the Windows 10 start screen. Tap the Home button, tap the Settings button on the left edge, and then tap System. From the left menu, tap Display and you'll find a slider for Adjust brightness level.

Screenshot by Matt Elliott/CNET

Next, tap Battery Saver from the left menu. Tap the toggle switch to turn on Battery saver. If the toggle switch is grayed out, unplug your laptop so it's running on battery power and the toggle switch will become active. Battery saver is a new feature with Windows 10 that limits background activity and push notifications to extend battery life.
By default, Battery saver turns on when your battery falls below 20 percent. Tap Battery saver settings to adjust this percentage. Also on the Battery saver settings page, you can check a box for Lower screen brightness while in battery saver to further extend battery life.
Lastly, tap Power & sleep from the left menu and select times for Windows 10 to turn the screen off and put your PC in sleep mode to avoid needlessly draining your battery while your laptop sits idle.
For more, read about Window 10's built-in battery-saving mode.

Don't forget keyboard backlighting

Similar to powering the display backlight, powering keyboard backlights can also be a big drain on your battery. First, make sure you turn off your keyboard backlights when you don't need them. Secondly, both OS X and Windows 10 have settings that will kill keyboard backlights after the laptop sits idle for a time of your choosing. This setting varies by manufacturer with Windows 10, but on OS X, you'll find it in System Preferences > Keyboard.

Turn off wireless and unplug peripherals

While the display is the primary culprit for draining your laptop's battery, I still want to leave you with two pieces of tried-and-true battery life advice.
1. Turn off Wi-Fi and Bluetooth when they aren't needed. Both wireless adapters use battery power to scan for networks and devices and keep you connected.
2. Unplug any peripherals when they aren't in use. An unpowered peripheral draws power from your laptop, which means it'll drain the battery when the laptop isn't plugged in.