Electric hot water bags are designed with a simple yet effective heating mechanism. The bag contains a water compartment in which water is heated by an internal electric heating element. The heating element is powered by electricity, which transfers heat to the water, causing it to warm up.

The bags are usually equipped with temperature control features to allow users to adjust the heat to their preference. In addition, some models come with timers to ensure the bag turns off after a set period, preventing overheating or prolonged use. The flexible design of electric hot water bags ensures they can be comfortably placed on different areas of the body, such as the back, neck, or abdomen, to provide relief from cold or muscle aches.