Not all demand water heaters have this electrical device. You should check with the manufacturer for models that have this feature. Some models use batteries to trigger the IID, wheras others require an permanent electrical source. Most tankless models have a life expectancy as long as 15 to 20 years. In contrast, storage tank water heaters last 5 to 15 years.
Most tankless models have easily replaceable parts that can extend their life by many years more.
Depending on your water conditions, periodic maintenance is required. For example, many units incorporate a water inlet filter. This inlet filter must be periodically inspected and cleaned to ensure optimum flow and efficiency. Failure to descale the heat exchanger can result in premature failure and gradual loss of heating efficiency and flow volume. The following table compares several popular brands of gas demand water heaters.