One of the most popular type of water heaters used is the storage tank with a burner on the bottom. This type has the temperature setting on the control valve, and stores the water at the a set temperature until your ready to use it. Problems with the storage tank heater is you can use up all the hot water before the flame can heat the cold water that is coming into the tank to replace the hot-water going out. Some people add more tanks into the line to increase the amount of stored hot water. Piping arrangement for this type of install can be done in series, or parallel, basically, you use all the water at the same time or, you use one tank to pre-heat the water, and the other tank to finish heating the water. One tank always plays a larger role in heating the water, while the other tank gets less burner activity.

Note about gas water heater design change in Canada.

On January 1 2005, all gas water heater manufactures were required to make their gas water heaters more resistant to explosions. This change required that the traditional access door on the bottom where the burner assembly is located be sealed. Some manufactures changed the type of thermocouple, and relief valve so that parts from the old design would not fit the new design. The up-side to this is ease of lighting as it now has an igniter much like the some BBQs. Down side, the cost of new heaters has gone up.

Electric Water Heaters:

Electric water heaters are mostly use when natural gas is not available. If you have a choice of natural gas vs. electric, gas is the preferred and cheapest to run solution.  A 1991 study by the Department of Energy (DOE) rated residential energy sources by the average dollar cost per million BTU'S of heat they produce. Natural gas was found to be $6.05; heating oil $9.30; propane $9.74; and electricity a whopping $24.15. Obviously, these amounts vary with local energy prices and do change over time, but in the relative world of energy, natural gas is by far the cheapest, most convenient fuel for water heaters.
There are 220 volt and 110 volt options along with different size water tanks to choose from. It is a good idea to install a timer on the electric tank to shut the tank power off when not needed, as well as install a vacuum breaker in the water line to prevent the water draining out in emergency  situations requiring the main water supply to be shut off. If the water drains out, and the power is left on, the elements will burn out, leaving you with expensive repairs. Unlike the gas heaters, twining the tanks would not be a good idea as the cost to keep the water warm can be very high. You can mount a instant water heater on the outside wall, remove the elements and use the tank as a storage tank if gas/oil/propane were to become available. One model is the Seahorse®.

Tank-less water heaters:

Demand water heaters are common in Japan and Europe. They began appearing in the United States about 25 years ago. Unlike conventional tank water heaters, tank-less water heaters heat water only as it is used, or on demand. A tank-less unit has a heating device that is activated by the flow of water when a hot water valve is opened. Once activated, the heater delivers a constant supply of hot water. The output of the heater, however, limits the rate of the heated water flow.

Demand water heaters are available in propane (LP), natural gas, or electric models. They come in a variety of sizes for different applications, such as a whole-house water heater, a hot water source for a remote bathroom or hot tub, or a boiler to provide hot water for a home heating system. They can also be used as a booster for dishwashers, washing machines, and solar or wood-fired domestic hot water system.

You may install a demand water heater centrally or at the point of use, depending on the amount of hot water required. For example, you can use a small electric unit as a booster for a remote bathroom or laundry. These are usually installed in a closet or underneath a sink. The largest gas units, which may provide all the hot water needs of a household, are installed centrally. Gas-fired models have a higher hot water output than electric models. As with many tank water heaters, even the largest whole house tank-less gas models cannot supply enough hot water for simultaneous, multiple uses of hot water (i.e., showers and laundry). Large users of hot water, such as the clothes washer and dishwasher, need to be operated separately. Alternatively, separate demand water heaters can be installed to meet individual hot water loads, or two or more water heaters can be connected in parallel for simultaneous demands for hot water. Some manufacturers of tankless heaters claim that their product can match the performance of any 40-gallon (151-liter) tank heater.

Solar Water heaters:

One of the cheapest ways to heat your water (after equipment purchase) is with solar energy. Systems include a solar collector and a storage tank. The collector collects the heat energy with a fluid (water or diluted antifreeze for example) and the sun. It is then pump down to a heat exchanger to have the energy transferred into a storage tank for use. A good description of the process can be downloaded by clicking here. Troubles you can have range from faulty pumps, frozen collector lines or damaged collectors. For instant help with this and other solar energy products, call Brent " 403 568 9999 or the web-site " www.yourenergycompany.net

Indirect water heaters:

If you have a hydronic heating system in your building already, a great way to heat the water is with "indirect-fired water heater tank." The storage tank holds about 50 to 100 gallons of hot domestic water. This arrangement allows the boiler to fire less frequently in the summer and thus save energy. It works by using a small circulator that extracts heat from the boiler as it fires and then transfers the heat to the storage tank by way of a heat exchanger. During the winter this is very good way of making domestic water hot because the boiler is already hot for heating the building. In a way, the domestic hot water is almost free as long as the boiler needs to heat the building too. Seasonally, the efficiency of an indirect-fired water heater ranges from about 80% in the winter to about 70% in the summer. It also has the side benefit of delivering a much higher flow rate at a more predictable, and comfortable, temperature to the occupants.

Combined space heating/domestic hot water systems are not limited to hydronic (boiler) systems. Some are integrated with a forced-air furnace. A heat exchanger is used to heat the domestic water or a liquid-to-air heat exchanger to warm room air. Also, since a hot air furnace is being used it is relatively inexpensive to add space-cooling capabilities (air conditioning) to this type of system.

How do hot water heaters work?
 

Tank Type:
One of the most popular type of water heaters used is the storage tank with a burner on the bottom. This type has the temperature setting on the control valve, and stores the water at the a set temperature until your ready to use it. Problems with the storage tank heater is you can use up all the hot water faster than its being reheated. Some people add more tanks into the system to increase the amount of stored hot water. Piping arrangement for this type of install can be done in series, or parallel, basically, you use all the water at the same time or, you use one tank to heat the water, and the other tank to store the heated water.

Instant Type:
During the past 6 years, newer instant water heaters have been making a scene in Calgary. The technology has improved in making these types of water heaters more efficient and practical for everyday use.  They work by only have the gas or electrical element come on when there is a need for hot water. The water travels down a series of tubes that are positioned over a gas burner, or part of an electrical element. Down side to these units would be the inability to have your laundry and dishwasher going while you trying to take a shower. Volume is limited unless you install more units into the piping system to better heat the water.
 

 Solar Type:
No much to be said here, you install thermo collectors on the roof, along with the equipment supplied with the solar water-heater kit, the you set. The sun heats the water year round. Saving very depending on the amount of water you use and how many collectors you in stall.