A water boiler is any device that is used to boil water such as a domestic kettle or a commercial water boiler. Kettles are a container with a spout for pouring, a handle and a lid. Inside the kettle is a heating element which allows an electric current to flow through the water and bring it to boiling point. The kettle switches off in response to a thermostat once the required temperature is reached. A commercial water boiler is a larger, wall mounted unit with a powerful heating element inside and a small tap on the front. Commercial boilers are permanently plumbed in and provide instant hot water for large numbers of people in canteens, offices and cafes.