An immersion water heater runs on electricity and heats the water via a heating element immersed inside the water tank. They are set up much like gas water heaters but don't have the same ventilation requirements.
Immersion heaters have an insulated water tank with a cold tube to carry water in, and a hot tube to send the water where it's needed inside the home. The heating is controlled by a thermostat that turns on the heating element when the water goes beneath the pre-set temperature.
When the heating element is on, electric power runs through it, creating heat. Unlike a gas water heater, the heat does not go through a heat exchanger. Instead, it flows directly into the tank's water supply.
Immersion water heaters are more energy efficient than gas. A conventional electric model averages a 90 percent efficiency rating, while a conventional gas water heater averages a 60 percent rating. Electric power is generally more expensive than natural gas.
Gas does outperform the electric model in water heating speed and recovery time. A gas heater can heat 50 gallons in roughly an hour, while an electric heater takes several hours to heat the same volume. Large families might want to consider the gas version. Gas heaters also work during a power outage.