Have you ever put your laptop in your bag, only to pull it out and find it's hot and the battery is drained, even though you put it to sleep? Turns out Windows may have gotten in its own way, preventing it from fully going to sleep.

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Modern standby is the sleep state most newer PCs go into when you tell them to sleep. It cuts power to the display and CPU, but allows for minimal background processes to continue, so you can have that instantaneous wake time. This mode might not be the most efficient way to save your battery, however. Here's the breakdown.

Your PC can be in one of six states, identified by "S" followed by a number. For example, S0 refers to the "Working" state: on, and operating normally. At the other end is S5, which means that it's powered off. There are a few different states in between, but not all are commonly used.

Most newer PCs enter a low-power state, often called "Modern Standby," when you tell them to sleep. This is like a better-optimized form of sleep that lets your PC quickly switch back to a working state (S0) -- similar to how your smartphone wakes up instantaneously.

In this state, the display is off, as are most core components, but there is some very limited background activity so your computer can snap back to work at the touch of a button. In theory, battery life should drop to a trickle. More on that in a moment.