Instead of having a water heater that heats up a certain amount of water and holds it until it is used, the shower head heats up the water as it goes through it - using an electrical current. Yes, that's right - everything your momma told you about not mixing water and electricity is thrown out the window here!
There are 220 volts of electricity pulsating through the water as it flows through the head, effectively heating it. Sometimes the water gets a little "zingy"!! And God help you if you touch the shower head while you're in the shower - it gives quite a jolt! The more water pressure, the colder the water - so if you want to have a hot shower, you have to minimize the amount of water coming out so it can be heated.
Below is a picture of our sink...it's pretty small!!!