On demand point-of-use or instant water heaters are relatively small appliances that produce hot water instantly, when we need it. Most do not incorporate any sort of tank, and only heat the water that is required. You turn on the faucet and you have hot water. It’s as simple as that.

Generally on demand water heaters are considerably smaller than regular water heaters – largely because they don’t incorporate a tank. This reduces the need for lengthy pipe work and makes them particularly useful for sinks or basins that are not located within a kitchen or bathroom where most plumbing pipe work is located. They are also ideal for heating hot tubs, because these are generally located away from normal plumbing pipes and fittings. They may, of course, also be used in kitchens, bathrooms and in laundries, depending on your needs.

Traditionally instant, tankless water heaters were specifically designed for point-of use. But today there are an increasing number of units available that will heat water for the whole house. So the hot water is available “on demand”, but not necessarily at the point of use.

The most basic instant water heaters have either an electric element that heats the water, or a gas burner of some sort. The most advanced type is the low-mass water heater which uses different technology and is able to supply considerably more hot water than other types. These hi-tech water heaters are usually gas-fired and they incorporate an electronic ignition as well as a power exhaust. They have the capacity to be connected to an external storage tank, making them more versatile than the more traditional types.

Some electric products

Stiebel Eltron from GO Tankless (www.gotankless.com) makes leading edge tankless water heaters that are very popular in North America. Their units feature sensors and microprocessors that not only automatically adjust the water flow rate and pressure, but also the temperature of the water.  The company maintains that their heaters can enable you to cut your water heating costs by as much as 50%, which clearly makes them “green”.

When a hi-tech Stiebel Eltron tankless water heater is activated – by turning on the water faucet or tap – the flow sensor recognizes that the water is running and its heating elements go on. Voila! When you turn off the faucet, the unit switches off and immediately stops using energy. Manufactured according to high German engineering standards, these units come in a high quality aluminum case and they have heating chambers that are made from copper.

Bosch (www.boschhotwater.net) makes two electric tankless water heaters designed specifically for the North American region. Both branded PowerStar, they are designed for all uses. One model provides 3.7 gallons per minute at 105 °F, either to two sinks at the same time, or to a shower or a bathtub. Alternatively it provides 3 gallons per minute at 115 °F to two sinks or to the dishwasher. The other model is smaller and provides 2.3 gallons per minute at 105 °F to a shower, bathtub or washing machine. Alternatively it delivers slightly less (2 gallons) at a slightly higher temperature (at 115 °F) if connected to a sink or dishwasher. The smaller model is not recommended in areas where the average annual ground water temperature does not rise above 60 °F – which eliminates all but the southern-most states in the US and all of Canada.

Bosch also produces an Italian-designed mini-tank point-of-use water heater that incorporates a glass-lined tank.

Gas products

Gas-fired instant water heaters generally provide a much higher flow rate than those powered by electricity. But they won’t all enable you to use more than one appliance at a time. The answer here is to install more than one on demand heater so that you can have a shower or bath when you are washing dishes or clothes. Even buying two units will guarantee that you will save bucks.

However, there is a down side. Gas-fired unites can also waste energy, particularly those that have a pilot light that burns all the time. The costs of operating pilot lights do vary though and you can usually ascertain this figure before you buy your gas water heater. If the manufacturer cannot give you this information, think twice before buying it. Some models have intermittent ignition devices that don’t stay on all the time, alternatively you might consider simply turning off the pilot light and relighting it when you need it. This is, after all, an”instant” water heater.

Uniongas (www.uniongas.com) produce tankless water heaters that use natural gas. Like electric water heaters, when the faucet is turned on, a flow switch is triggered that activates, in this case the burner that heats the cold water. The water heats quickly to the required temperature, and then stops heating as soon as the faucet is turned off.

Bosch manufactures several tankless gas water heaters. At least two of these are certified by ENERGY STAR and both of these enable you to run at least two appliances that use hot water at the same time. These heaters are larger than their electric unit counterparts, and they feature electronic ignition.

Takagi (www.takagi.com) also manufactures gas supply water heaters. A well-established Japanese company that entered the North American market more than 15 years ago, the water heating units feature water sensors that detect the flow of water into the unit. This makes them automatically ignite so that the water that is circulating through the coils in the heat exchanger instantly heat the water – in only a fraction of a minute. When the hot water faucet is turned off, the unit shuts down immediately.

Save energy with instant water heaters

If you aren’t convinced that tankless, on demand water heaters are not the way to go, perhaps the US Department of Energy will persuade you otherwise.

“Demand (tankless or instantaneous) water heaters provide hot water only as it is needed. They don’t produce the standby energy losses associated with storage water heaters, which can save you money.”

That’s what we already told you!


A good quality demand or instant water heater is likely to cost you more than most conventional tank storage water heaters. But generally you will find that both energy and operating costs are considerably lower.

Long term it is certainly an option to consider.


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