Demand (Tankless) Water Heaters are common in Europe and Japan
Demand Water Heaters are common in Japan and
Europe. Approximately twenty-five
years ago, Demand Water Heaters appeared in the United
States. Unlike tank water
heaters, a tankless unit heats the water only as it is used,
or on demand. The
heating element in the tankless unit is activated by the
flow of water. The system
will continue to deliver heated water as long as it is
needed. The rate of the
heated water flow is limited by the output.
A normal household will spend more than 20% of its yearly
energy expenses on heating
water. The operating cost for a gas or electric storage tank
hot water system is
about $200 or $450, respectively. Conventional tank hot
water heaters raise and
maintain the water temperature to the degree setting on the
tank. This is normally
between 120o F-14oF, or 49oC-60oC. The system heats the
water continuously even
if no water is drawn from the tank. This called standby
losses the heat conducted
and radiated from the walls of the tank-and in gas-fired
water heaters-through the
flue pipes. This represents 10% to 20% of a household's
annual water heating costs
that is wasted. Instantaneous or tankless water heaters will
reduce this expense.
