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Energy Factor
Energy Factor (EF) = a measure of the overall efficiency of a water heater• Includes:
―Recovery efficiency―Standby losses―Cycling losses
Energy Conservation
New homes:• Keep hot water
pipe run as short as possible
• Use a manifold plumbing system
Energy Conservation
Water heater setting• Temperature = 120°F– Provides plenty of hot
water– Decreases risk of
scalding– Select dishwasher with
booster heaters
Gas Water Heaters
Energy Factors (EF) for ENERGY STAR® Gas Water Heaters
Type Energy Factor
Gas Storage (ending 8/31/2010) ≥ 0.62
Gas Storage (beginning 9/1/2010) ≥ 0.67
Whole-home Gas Tankless ≥ 0.82
Gas Condensing Storage ≥ 0.90
Gas Water Heaters
Gas water heater efficiency is affected by:• Burner design• Shape of the flue baffles• Amount of surface area between the flue gases
and the water• Presence of blowers for venting and delivery of
combustion air
Gas Water Heaters
Fuel-fired water heaters, in conditioned space:• Must be in a sealed mechanical room
―Fresh air inlets• To avoid the sealed mechanical room
―Use a fuel-fired water heater that includes provisions for outside combustion air• Direct-vent unit with a double flue pipe
Gas Water Heaters
Higher efficiency units have:• Blowers for venting and delivery of
combustion air• More sophisticated energy features
―Electronic ignition―Flue dampers―Condensing heat exchangers
• EF > 0.90
Electric Water Heaters
Electric hot water heaters are generally more expensive to operate than gas units.
However, as energy prices change:
Heat Recovery Units
Heat Recovery Unit = Desuperheater
• Recovers excess heat from air conditioner or heat pump to provide “free” hot water
Heat Recovery Units
In summer:– Desuperheater can
usually provide 100% of the hot water needs of a family and improve the efficiency of the air conditioner
In spring and fall:– Desuperheater is
ineffective
In winter:– Desuperheater is more
effective and saves money
Heat Recovery Units
Performance of a desuperheater is affected by:• Size and efficiency of the water heater and cooling
equipment– Cost $550 to $750– Annual savings = $50 to $180– Make sure that it does not void any mechanical
equipment warranties– Check the water supply to see if any buildup may occur
Solar Water Heaters
Images Courtesy: http://www.eere.energy.gov/consumer/your_home/water_heating/index.cfm/mytopic=12770
Solar Water Heaters
Cost effective option because:
• Current cost of energy• Tax incentives at state and federal levels• Can be oversized– Used to assist with heating a home
On Demand Water Heaters
Save energy:• No storage
tank• Gas-fired units
usually heat water more efficiently than gas tank type water heaters