The concept of tankless water heating is pretty simple - instead of heating water
and storing it in a tank where energy is lost throughout the day, tankless systems
heat water on demand, only as hot water is actually needed and used. This concept
originated in Europe and Asia where tankless heaters have been used for decades.
In the early 1990's, as energy prices started to rise in North America and as consumers
began to pay more attention to "green" technologies, tankless water heating technology
migrated to the U.S. and Canada. The early models, which were generally designed
for low-flow point-of-use applications only, were not very sophisticated, but offered
consumers on demand water heating and the opportunity to reduce their cost of water
heating and associated environmental footprint.
Today's tankless water heaters are much more powerful and are capable of handling
the demands of a whole household as well as many commercial applications. While there
is a huge variation in technology, the general concept behind each unit is the same:
A flow sensor detects when you turn on a hot water faucet and activates the tankless
water heater. A series of heating elements then heat the water and will continue
to do so until the flow sensor recognizes that the water has stopped flowing (you
turn the faucet off).
Since the heater only runs for a few minutes per day as opposed to cycling on and
off all day long like a traditional tank-type water heater, a substantial reduction
is energy costs can be achieved - generally 30 to 50%. Since a tankless water heater
can literally run forever without running out of hot water, there is no need to overheat
the water anymore as is done with conventional heaters to ensure they do not run
out of hot water. This creates additional energy savings and reduces the formation
of hard water scale. As a result of this, and the fact that full water pressure is
maintained throughout a tankless heater, they are less prone to problems related
to mineral and sediment build-up. Accordingly, they are backed by much longer warranties
than conventional water heaters, and indeed, they do last much longer. Of course,
due to their small size (about the size of a brief case, tankless water heaters also
save space.
Despite the fact that all tankless water heaters are based on the same core concept
of heating water on demand only as it is needed, there is a huge variation in technologies
available, ranging from rudimentary on/off models, to heaters that offer automatic
thermostatic control regardless of flow rates and the incoming water temperature.
Accordingly, there are big differences in performance too.
