As water is demanded from a conventional tank, cold water begins to flow immediately into the tank. The cold water immediately starts to dilute the heat of the existing water in the tank, effectively reducing its capacity. As more and more water is drawn from the tank, the overall water temperature in the tank continues to drop, eventually becoming too cool to use comfortably for most applications (showering, etc.). Because of this inefficient process, if you have, for example, a 60-gallon tank, you actually only have only about 45 gallons of useable hot water. The other 15 gallons are lost as cold street water is added to the tank during the usage process. We have all experienced the icy blast when a traditional tank of hot water.
Once this occurs, we must also wait a considerable
time for the heater to bring all of the water in the tank back up to a
usable temperature. The speed at which this is accomplished is referred
to as the refresh or recharge rate. To increase the refresh rate and
reduce the effective of temperature declines during drawdown of the hot
water, traditional water heaters are often set at very high temperatures
- 130 to 140F. Basically, tank-type heaters require you to heat the
stored water to an exceptionally high temperature in order to provide an
adequate supply of hot water. This temperature is typically far higher
than what would be comfortable or safe for showering or other household
uses. You must first pay to heat this water only to cool it again by
adding cold water to make it comfortable for use. In other words,
you are paying for electricity which heats the water to a much higher
temperature than you will ever actually use. Also, you must pay
to keep the water in the tank hot all day, not just for the few minutes
of each day that it is actually needed. This results in a substantial
amount of wasted energy - wasted money too! In addition, a conventional heater is consistently radiating heat
(loss), which also contributes to the re-heating rate and energy
consumption. This type of heat loss is often referred to as "stand by"
heat loss. Even today's highly-insulated tanks have a considerable
standby heat loss. Most conventional heaters have upper and lower
heating elements, one of which is cycling on or off 24 hours per day,
even when you're not at home. Using a tank to continually heat and store
water is akin to parking your car in your driveway and leaving it
running all night at idle until its next use. Simply by eliminating
stand-by heat loss alone, energy consumption can be reduced by 20% to
30%.
Furthermore, conventional heaters require a
substantial amount of space. Generally
located in closets, utility rooms or garages, they consume valuable
square footage that could be put to better use. Being the size of an
average phone book you can only imagine the amount of space savings
compared to a tank. Tankless Water Heaters heat water entirely on
demand, only when it is needed. Then a hot water faucet is turned on and
the water begins to flow, a sensor detects that hot water is being
demanded. This sensor effectively turns on the heating elements/heat
exchanger and a computer chip selects the correct power output to the
elements/heat exchanger based on the heat setting selected by the user,
the flow rate, and other parameters. The water flows across the internal
heating elements or heat exchanger and exits the unit at the desired
temperature. The start-up process takes a couple of seconds. The
tankless water heater will remain on until the hot water faucet is
closed. As soon as the flow sensor detects that water has stopped
flowing, the power to the unit is turned off completely. So when hot
water is not being demanded, absolutely no energy is being consumed. The
stand-by heating loss is completely eliminated. Furthermore, since a
Another noteworthy problem with traditional water
heaters is their susceptibility to minerals, sediments, and age. The
average lifespan of a traditional tank-type water heater in North
America is less than 12 years. Unfortunately, most tanks, once they have
reached the end of this short
tankless water heater has no refresh rate (it is instantaneous), there
is no need to overheat the water to 130 or 140F (or higher) as with a
conventional tank. You can select an output temperature that matches your
actually needs (usually about 105F). This saves considerable
energy.
service life, are destined for the landfill - hardly an
environmentally-friendly or long-term cost-effective solution. Tankless
water heaters, on the other land, have far longer service lives that can
double a standard tank model.