I know this is a really old post, just thought this would be useful to others;
On your Mac model / macOS version, type "man pmset" in Terminal to see what the values are for your Mac - seems not all models and/or macOS versions adhere to the same numbering scheme.
hibernatemode supports values of 0, 3, or 25.
Default: hibernatemode, standby and autopoweroff are all set to 0.
hibernatemode = 0 default on desktops.
The system will not back memory up to persistent storage. The system must wake from the contents of memory; the system will lose context on power loss. This is, historically, plain old sleep.
hibernatemode = 3 default on portables. The system will store a copy of memory to persistent storage (the disk), and will power memory during sleep. The system will wake from memory, unless a power loss forces it to restore from hibernate image.
hibernatemode = 25 is only settable via pmset. The system will store a copy of memory to persistent storage (the disk), and will remove power to memory. The system will restore from disk image. If you want "hibernation" - slower sleeps, slower wakes, and better battery life, you should use this setting.
On my MacPro (2013 model) both values 3 and 25 will powerdown the backlight of my (non-Apple) mouse (Logitech) and keyboard (Havit). The default settings would keep the backlights on - which can be quite annoying.
Boot time (64Gb RAM) with "hibernatemode = 3" is very fast, "hibernatemode = 25" only a fraction slower.
Also looks like a USB power switch may solve this issue for your cooling fan always on problem https://www.adafruit.com/product/1620?gclid=CjwKCAjw7vraBRBbEiwA4WBOn6hVzZM7s35DSGYQc_0Z75t31PJkJHFCGn-d79QxaudIA0l0N3DeNxoCmCoQAvD_BwE
– MrDaniel – 2018-07-30T14:50:59.160