Selecting a Hot Water Heater

We all need hot water heaters in our homes, so if you’re building one of your own, sooner or later you’re going to find yourself selecting a hot water heater.

There are various types of hot water heaters, and different ways in which they are heated – by electricity, gas, oil or solar power. But what they all have in common is the ability to heat cold water supplied by your local authority or municipality so that you can have hot water on demand when you shower, bath or wash clothes or dirty dishes.

While some water heaters don’t have tanks to store the water, most do.

Tank water heaters

Tank water heaters literally store water in a tank and heat the water in the tank. There are a variety of types (or models) that use the full spectrum of heating sources – electricity, gas, oil and solar.

Generally the way tank water heaters work is that as hot water is drawn from the top of the tank, cold water refills the tank from the bottom. If the heater is switched on, the water will be constantly heated. Of course nowadays we are all a lot more aware of the need for energy efficiency, and so we don’t keep our water heaters switched on all the time. A growing number of people are also realizing that some water heaters are more energy efficient than others.

Typically, an energy-efficient storage tank water heater will have at least one of these features:

  • insulation that will prevent loss of heat through the external walls of the tank (building the tank into a covered space and laying insulation material over it also helps),
  • a superior heat exchanger that is able to transfer more heat from the energy source to the water,
  • factory-installed heat traps that are designed to prevent hot water flowing out of the tank when it isn’t wanted, but allow water to flow into the tank.

There are also additional design features that make gas-fired storage tank water heaters more energy efficient, including:

  • electronic ignition rather than an old-fashioned pilot light that stays on continuously, using energy (however little),
  • a powered exhaust system,
  • a mechanism that controls and reduces heat loss via the flue vent,
  • condensing heat exchangers that are much more efficient than other types.

There are also new technology oil-fired water heaters that have high tech burners that improve energy efficiency.

Uniongas ( manufactures natural gas tank water heaters with three different venting options:

  • direct vents, that don’t require a chimney,
  • power vents, that don’t need a chimney but use an electrically powered fan,
  • conventional vents, that do need a chimey.

Solar water heaters also use tanks, but the water may be heated in a collector or a special liquid in the collector transfers the heat to the tank. Because weather conditions do affect the efficiency of solar water heaters to warm the water, they are often used in conjunction with an electric element that kicks in when needed – especially in winter.

Instant water heaters

These are water heaters that don’t incorporate a tank and they only heat water when it is required. They are generally small appliances that are fitted so we can get instant hot water from a sink or basin that is not connected to a regular tank water heater.

The most basic type of instant water heater either has an electric element or a gas burner. Low-mass water heaters use a different, more advanced technology and they are capable of supplying a lot more hot water than the traditional type of instant water heater. These are usually gas-fired and they have both an electronic ignition and a power exhaust. They can be connected to some sort of an external storage tank if this is required.

Stiebel Eltron from GO Tankless ( is a popular make of electric tankless water heater in North America. Their primary claim to fame is advanced flow control technology that automatically adjusts the water flow rate.

Uniongas manufactures natural gas tankless water heaters.

Energy efficient water heaters

When it comes to selecting a hot water heater, it makes sense to choose one that is energy efficient.

In Canada, the efficiency of electric tank water heaters is measured by what is called either “standby loss” or “rating watts loss”. While low standby loss models are clearly the most energy efficient, it is also important to choose a heater that meets the needs of you and your family. If you select one that is larger than necessary (in terms of the volume of water you use), this will result in unnecessarily increased energy costs.

Be warned that an energy efficient electric water heater will cost you more than one that isn’t highly efficient, but the quality will be better and you will benefit from improved warranties.

The efficiency of both gas and propane-fired, as well as oil-fired water heaters, is measured by an “energy factor”. High energy factors are, not surprisingly, the most efficient in terms of both tank heaters and those that do not have tanks. If you are selecting a gas tank water heater, the same warnings regarding oversized tanks applies.

Rheem ( manufactures a wide range of different types of water heater. These include instant electric or “point-of-use” models, heat pump water heaters and both gas tank and tankless water heaters for homes.

The US Bradford White Corporation ( offers a comprehensive selection of products including natural and propane-fired gas water heaters, oil-fired water heaters, electric water heaters, indirect water heaters, and solar water systems. Laars Heating System Company ( manufactures gas fired boilers and volume water heaters. The company is a wholly owned subsidiary of Bradford White.

A.O. Smith Corporation (, which is headquartered in Wisconsin, designs and manufactures two brands of hot water heaters, GSW and John Wood ( GSW has both gas and electric models. John Wood, which is only available to installers, specializes in energy efficiency and has products that are ENERGY STAR rated.

In many countries there are tax rebates and other initiatives to encourage people to install solar and other energy efficient hot water heaters.

In British Columbia and Ontario homeowners are eligible for tax-free government granters when they install gas or solar water heaters or an electric heat pump hot water heater.



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