Electric kettles (also known as hot pots) and hot water heaters can heat hot water for a variety of different uses - not just for coffee. They are much faster than using a stovetop kettle, or even a microwave (which takes several minutes and can be dangerous). If you often find yourself on the go, but you absolutely must have that cup of tea (or soup, or oatmeal...) before you go out the door, you should consider getting a hot water heater.