## 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.