How To Select The Right Sized Heater...

Part 1 Energy Factor

The two factors that you have to know before you buy a water heater are Energy Factor and First Hour Rating. These two factors are explained in detail and you can go there by clicking the relevant links below...

Hot Water Heaters Energy Factors

First Hour Rating For Hot Water Heaters

Knowing the cost of the energy source will help you make a much more informed decision regarding the water heater that you are going to buy. Everyone knows that electricity is the most expensive energy source. We are going to concentrate on gas fired hot water heaters only on this page.

1. Energy factor: The energy factors between gas tankless and gas storage heaters differs greatly. Other gas hot water heaters use either natural gas or propane fuel.

Knowing the energy factor will help you calculate the energy used...

Knowing the energy factor will help you calculate the amount of energy used by your home per year. You must use the cost of gas used as $ per therm (1 therm is = 100,000 BTU). Average US cost per therm is $0.6 as assumed here.

Natural Gas, Propane Heating Oil Costs For Water Heating

You can use the table below to estimate your annual cost taking into account your approximate water consumption per day for every day of the year and you can see in the red section the impact that Energy factor per year. For example by comparing the purple line and the bottom red line, it is clear that if you use 65 gallons per day of hot water (77 degrees above cold water inlet) using an efficient .85 Energy factor unit that you will save (151.40-115.78 = $35.62) per year.

After a decade you will have saved $445. Remember that a gas fired tankless heater could have cost only $107 per year to perform the same job.

Water per day in gallons	50	55	60	65	70
Annual cost 100% Energy factor	$ 70.29	$ 77.32	$ 84.35	$ 91.38	$ 98.41
Energy factors impact showing annual cost of gas for different flows and different Energy factors
0.45	$ 156.21	$ 171.83	$ 187.45	$203.07	$218.69
0.5	$ 140.59	$ 154.65	$ 168.70	$182.76	$196.82
0.55	$ 127.81	$ 140.59	$ 153.37	$166.15	$178.93
0.6	$ 117.16	$ 128.87	$ 140.59	$152.30	$164.02
0.65	$ 108.14	$ 118.96	$ 129.77	$140.59	$151.40
0.7	$ 100.42	$ 110.46	$ 120.50	$130.54	$140.59
0.75	$ 93.72	$ 103.10	$ 112.47	$121.84	$131.21
0.8	$ 87.87	$ 96.65	$ 105.44	$114.23	$123.01
0.85	$ 82.70	$ 90.97	$ 99.24	$107.51	$115.78

Do take note that any percentage saving in Energy Factor has a lower percentage saving effect upon the bill you will pay .... this leads to what can be considered misleading advertising.

To give you an example for any hot water heater (tankless or storage) an Energy factor of 0.85 is 30.7% better than an Energy Factor unit of 0.65 but the cost saving is not 30.7%. In actual fact the cost saving is only 23.5% ($35.62 divided by $151.0)

Tate Industries Hot Water Storage Tank Heaters Gas and Electric...

This table below shows Energy factor difference between best and worst units for different types of tankless and storage tank hot water heaters. This table clearly shows that tankless hot water heaters are certainly more efficient than storage hot water heaters ... but do not forget that this is only one factor that will determine your final choice

Type	Energy Factor Parameter	Energy Factor
Storage Propane Gas heater	MAX value	0.65
Storage Propane Gas heater	MIN value	0.46
Storage Propane Gas heater	AVG value	0.56
Storage Natural gas heater	MAX value	0.65
Storage Natural gas heater	MIN value	0.46
Storage Natural gas heater	AVG all values	0.56
Storage Dual gas heater	MAX value	0.63
Storage Dual gas heater	MIN value	0.48
Storage Dual gas heater	AVG value	0.57
Tankless Hot Water Heaters ... gas	MAX value	0.85
Tankless Hot Water Heaters ... gas	MIN value	0.64
Tankless Hot Water Heaters ... gas	AVG all values	0.75

The Energy Factor in simple terms means that if the Energy Factor is high then the annual cost of power to run the tanklless hot water heater or the storage heater will be lower than it would be if the Energy Factor was low. Gas tankless water heaters have an Energy Factors that ranges between 0.64 and 0.82

The First Hour Rating is the amount of hot water the heater can supply in an hour. If you are using a storage tank system then this means that the tank will be full of hot water at the beginning of the first hour.

You can read a wide range of water usage articles. They discuss the use of water in the house and home ... topics covered include filters, heaters, softeners and water in the garden.