No the term is “tempered”. Some systems like those used in large buildings blend hot water and cool water to “temper” the water that circulates through the building.So, I guess it takes hot water and heats it? So, what is hot water anyway? What temperature makes it hot? I think you were going for "temperate" water heater.
You mean they can be used to heat water. A water heater is "made" to heat water. A microwave is not "made" to heat water.Well, it’s hot water heater because of common usage. But I hear folks just say water heater and people usually understand. Of course a microwave or campfire can also be a water heater.