Energy Factor in Water Heaters

What is Energy Factor

Energy Factor
is the common name for a number of standardized metrics used to measure the
energy efficiency of several home appliances. The Energy Factor for each
appliance category is measured differently so you cannot really compate a water
to heater to, for instance, a dishwasher. In this article, I discuss Energy
Factor as it relates to water heaters.
Energy factor
in water heaters is essentially a ratio of the energy input to the heat energy
that is transferred to the water that comes out of the unit. To calculate the
efficiency at a most basic level, you just need to know the temperature and the
mass of the incoming water and how many degrees fahrenheit it was heated inside
the unit. This will tell you the total amount heat energy that was added to the
water i.e. the heat output of the water heater. Then, you take a look at how
much electric, propane or natural gas was used by the unit during this time.
The ratio will give you the efficiency. What makes Energy Factor superior to
the basic calculation described here is the standardization. There are strict
conditions under which the water heaters are tried for their efficiency and the
result allows you to compare any two devices without beign misled by
commercials or vendors.


Energy Factor Measurement

Energy factor
test for residential water heaters of any kind takes 24 hours at a certain
temperature setting. During the first five hours at total 64.3 gallons of hot
water at a specific temperature is drawn from the units in six equal draws with
1 hour in between. Then the water heater is left to run by itself for another
18 hours. The last 18 hours are for simulating the standby losses that occur in
storage water heaters. A tankless water heater uses no energy during this time
and ends up with a higher energy factor. At the end of the test, an elaborate
formula is used to calculate the energy factor. An energy factor of 1.00 means
a hundred percent efficiency while 0,85 means 85 percent efficiency.


What Energy Factor Do Different Types of Water Heaters Have

Prior to the
new efficiency regulations that became effective in 2015, an ordinary storage
water heater had an energy factor of 0.50 on average but such units can no
longer be retailed. Now, tank water heaters that run on natural gas or propane
must have at least an 0.60 energy factor and the number get s higher as the
tank size gets higher. Tankless water water heaters require at least 0.82 but
condensing tankless water heaters usually are much more efficient and can have
energy factors upto 0.98. As for electric water heaters, the energy factor must
be above 0.95 for small units. Electirc water heaters larger than 50 gallons
must have an energy factor of 1.92. This can sound stupid to someone with some
physics knowledge but little idea about the newest techologies in water heater
industry. There are heat pump water heaters that work similar to your fridge
but only in the reverse direction. These units can heat water with very little
electric energy by taking the heat from the surroundings and have energy
factors above 2.00.


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