Yes, they have a habit of falling off. They run the cold water to the bottom of the tank and push the hot water up to the outlet. When they fall off, the cold water is introduced into the hot water, cools it off and turns on the heater's 4500 watt (usually) element.
I have a whole house electrical monitoring system that it appears several people here could benefit from. It's called The Energy Detective (TED). I certainly don't endorse it because it has given me the fits over the years and I am banned from their forum because I questioned their support and design
but it IS very accurate to within a dollar or two of my actual bill. You can see the occasional spikes as my water heater comes on. The other ones are my stove and heat pump (not running the pellet stoves).
View attachment 128316