Typical Tank Water Heaters
Typical water heaters use both conduction and convection when heating water.
When water comes in direct contact with metal heating elements, only the water in the immediate area of the heating element is heated efficiently. (Conduction) Over time, these elements corrode and lose their heating efficiency. In hard water conditions, these heaters can lose 50% of their heating capacity in as little as 6 months.
As the heated water rises, it heats the surrounding water throughout the tank. (Convection)