Unfortunately, there were tons of tutorials on INstalling, but nothing at all on UNinstalling Energy Plus, so I decided to change that.

Windows

1. Go to the directory where Energy Plus is installed, typically This PC \ Local Disk (C:) \ EnergyPlusV9-#-#.
2. Look for maintenancetool.exe and run it.
3. Under the window that pops up, select "Remove all components" and follow the various prompts.

See screenshot below for example:

Note: This method was tested with Energy Plus 9-5-0 on Windows 10. It should work for EP 8-0-0 and newer on Windows 7 and newer.

Linux

1. In the Terminal, go to the directory where Energy Plus is installed. This can vary between distributions. On Ubuntu 20: /usr/local/EnergyPlus-9-#-#. Note: for those not familiar with the Linux command line, in most recent distributions right click in the file manager has an option to open in Terminal.
2. Run bash uninstall.sh
3. Approve any prompts that appear, then wait for it to complete.

Example:

Note: This method was tested with Energy Plus 9-5-0 on Ubuntu 20. It should work for EP 8-0-0 and newer on most modern Linux distributions.