Demand Water Heaters Explained

Demand Water Heaters are also known as Tankless or Instant Water Heaters. The reason for that name is that they provide hot water only when it's demanded. In this way, a great level of efficiency is achieved, which results in lower electricity or gas bills, depending on the type of water heater.

Since hot water is only produced on demand, demand water heaters do not have a storage tank. Instead, the cold water runs through a pipe into the unit. If it's an electric demand water heater, then an electric element does the heating. If it's a gas model, a gas burner heats the water. One or another, demand water heaters deliver a constant supply of hot water immediately when needed. You no longer have to wait for a storage tank to fill up with enough hot water. Typically, Tankless Water Heaters provide hot water at a rate of 2 - 5 gallons (7.6 - 15.2 liters) per minute. On an average basis, gas-fired Tankless Water Heaters will produce higher flow rates than electric Tankless Water Heaters. At most, an electric unit may be appropriate for small applications, such as a remote bathroom without a bath tub.

When buying a demand water heater, the first matter you must decide on is the fuel option - whether it will be gas-fired or an electric model. Generally, gas-fired systems are the most cost-effective ones. If you currently have an electric water heater and natural gas is available in your area, a switch might save you a lot of money. Electric water heaters are not highly recommended, because electric resistance is a very expensive way to generate heat. If you are thinking that the electric models are more environmentally friendly, you are wrong. The environmental benefits are nothing serious, since electricity is only as clean and efficient as the fuel (often coal) that generates it.

Compared to storage water heaters, the only drawback of demand water heaters is that they flow rate (although constant) might be limited, so they are not appropriate for absolutely every situation. Such tankless models perform much better when coupled with efficient uses and when the hot water uses in your home should be relatively close together.

There are point-of-use and whole-house demand water heaters. Both types work in the same basic way, but your choice should depend on three factors. First, the volume of water the unit is required to heat, measured as flow rate in gallons per minute (GPM). Secondly, the temperature of the cold water entering the unit. And last, the desired temperature of the hot water exiting the unit. Those three factors are what determines the type, size and possibly even the quantity of tankless water heaters you need.