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Do instantaneous gas hot water systems need electricity?

Do instantaneous gas hot water systems need electricity? The short answer is yes, most brands (Dux, Rheem, Rinnai) do need electricity. They do not use it to heat the water but to power an electronic sensor and temperature controller that improve the performance of the system. The electronic sensor and temperature controller are optional, so there are models that do not need electricity.

Most popular type of gas system

Instantaneous gas hot water systems are the most common type of gas water heater. The number of them installed in Australia in any one year is greater than any other type of gas hot water heater. Models are available to meet the needs of small and large residential households, as well as high demand commercial premises.

They require a medium-to-high purchase investment and involve medium-to-high installation costs. However, they generate running cost savings compared to most types of hot water systems.

Water is heated only when needed

Instantaneous gas hot water systems start heating the water only once the hot water tap is turned on. They continue heating water until the tap is turned off. For this reason, they are known as continuous flow gas hot water systems.

No storage tank

They heat water only as required. They do not have a storage tank. For this reason, they are also called tankless gas water heaters. Storing hot water is inefficient because of the tremendous heat loss they suffer, despite heavy insulation. They suffer much more heat loss than, say, electric or solar hot water systems, because it is not possible to insulate at the point where the gas flame heats the tank.

How do they work?

Instantaneous gas hot water systems heat cold water through a heat exchanger. The heat exchanger is heated by gas burners. When a hot water tap is opened, cold water flows into the heater. The cold water flows through metal piping that is coiled around the heat exchanger, like a serpent. The coiled piping allows the cold water to absorb the target amount of heat set by the thermostat.

Models with smart electronics need electricity

Models that need electricity have an electronic sensor that monitors the flow rate of cold water into the system. As the hot water tap is turned on and more cold water enters the system, the temperature controller increases the gas burn rate and vice versa. In other words, the controller regulates the gas burners to maintain the set temperature regardless of the volume of water flowing through the system, that is, regardless of how far the hot water tap is turned on.

These electronics help keep the hot water at an even temperature, regardless of how light or hard the hot water tap is turned on. The amount of electricity consumed by the sensor and controller is minimal and does not add significantly to running costs.

Government regulations apply

Gas instantaneous water heaters are subject to government regulations that set minimum standards of energy performance. In Australia, these are not in place for electric instantaneous water heaters.

Government regulations do not require instantaneous water heaters to exhibit an Energy Rating. The energy rating found on these heaters is set by the industry, not the government.