What is "Power Save Mode" in IntelliJ IDEA and other Jetbrains IDEs?

I see no readily available Google search results that answer this question. What is it, and what is it used for?

It's a setting to stop the IDE from automatically performing the full range of battery-hungry code inspections in the background as you type.

You should find that with powersave turned on, syntax errors will still get highlighted, but iffy code constructs e.g. missing docblocks, assignment inside conditional statements etc will not (assuming you have those inspections enabled). This means that you can save battery power when using your laptop and choose to run the inspections only occasionally by turning power save mode off for a minute or two, or using Code->Inspect code... to see what needs attention.

See Settings->Inspections to find out whether you can live without the specific inspections, which will depend on what language you are using. You can choose to run them individually on demand if you like using Code->Run inspection by name... if there are specific ones you need. More info here.

Naturally, this also applies to RubyMine, PHPStorm, PyCharm, WebStorm & AppCode as well.

IntelliJ power save mode is indicated by a Hector icon on the Status Bar at the bottom. If IntelliJ is running in power save mode, the Hector Icon will be faded.

In Power Save Mode, no code inspections are performed. Click on the hector icon to toggle the power save mode. https://www.jetbrains.com/idea/help/status-bar.html