Other products in development should reduce energy consumption in the near future. For example,
breakthroughs in the design of heat chambers result in higher heat transfer coefficients with thermal
efficiencies of 97 percent.
This technology is under research for commercial and manufacturing uses,
but with further R&D could be applied to residential heating systems as well.
Water heating is the second largest consumer of energy in homes, accounting for 12 percent of
total energy use. Given the current status of water heater technology, water heaters offer large potential
energy savings. Three technical improvements in water heating (heat pump water heaters, water heating
dehumidifiers, and heating water with waste heat) are described below. Other technology innovations
include solar water heaters, gas condensing water heaters, and tankless (or instantaneous) water heaters,
each of which is considered by the U.S. Department of Energy (DOE) to be promising technologies for
Another approach to reducing water heating energy is to improve the design of plumbing
within buildings by moving the water heater tank closer to the points of use, which wastes less energy
through thermal losses in hot water pipes.
The heat pump water heater (HPWH) moves heat from the house, garage, or outside air into the
water tank requiring less energy than would be needed to heat the water with an electric resist
ance water heater. An average HPWH uses less than 5 kWh of electrical energy to produce 64.3
gallons of hot water (the average daily hot water consumption for a typical U.S. household; a
conventional water heater requires 13.3 kWh to accomplish the same task). As a side benefit,
the HPWH can also provide cool, dehumidified air in the space where it is installed.
The water heating dehumidifier combines the efficiency of a HPWH with dedicated dehumidifi
cation. Humidity control is a growing issue for new houses, which are insulated so tightly that
outside air (along with its undesirable humidity) must sometimes be brought in to meet fresh air
requirements. Several working prototypes are being built, and laboratory and field testing will
Towards a Climate Friendly