Suspend-to-RAM uses some power, enough to keep the RAM alive. Suspend-to-disk shuts almost everything down and uses the same amount of power as a shutdown from software or the power button. But this still uses a small amount of power, so that things like Wake-on-LAN can work. You only get zero power use by switching off at the PSU or the power socket.
"Insanity: doing the same thing over and over again and expecting different results." (Albert Einstein)