What is the most common form of instantaneous water heater?

The most common form of instantaneous water heater is a tankless system. These units provide hot water on demand, eliminating the need for a storage tank. The system heats water directly without the need for pre-stored hot water, offering energy efficiency since they only operate when hot water is needed.

Tankless water heaters are popular because they can supply a continuous flow of hot water, which is particularly beneficial for households with higher hot water demands. They also tend to take up less space compared to traditional water heaters, making them an attractive option for modern living spaces.

While direct-fired heaters and other types of heat exchangers can be effective solutions for heating water, tankless systems are widely recognized for their efficiency, convenience, and ability to meet the varying demands of residential and commercial applications.