Criteria for Choosing a Water Heater Unit pt.2

Criteria for Choosing a Water Heater Unit pt.2
December 1, 2011 Lorelie

Water heaters are great innovation over the boiling of water on a pot or kettle just to have hot water you can use for bathing or for washing clothes of dishes.  It is convenient to have them as all you need to do is open the tap and you will have heated water flowing out of it.  This is the very reason why many households invest on water heaters.  The problem with water heaters is that they are not lifetime investments.  This means you will need to replace them after a decade or so, depending on their condition.

When replacing an old water heater with a new one, you need to consider certain criteria that will allow you to pick the right one that will suit your water heating needs.  In the first part of the ‘Criteria for Choosing a Water Heater Unit,’ the criteria mentioned were: Fuel Type, Size, Energy Efficiency, and Cost.  However, only Fuel Type and Size were discussed.  This second part on the other hand will discuss the remaining criteria.

Energy Efficiency – this is very important in a water heating unit as this easily translates into savings.  Before purchasing a water heater unit, it is essential to know how energy efficient the unit is.  Although more energy efficient water heaters cost more than the less efficient models, the savings you get from your utility bills will save you more money in the long run.  The list below shows the types of water heaters and their energy efficiency.

  • Solar Water Heaters – when it comes to the determining energy efficiency of solar water heaters, they Solar Energy Factor (SEF) as well as Solar Fraction (SF).  The Solar Energy Factor is the energy used by the system divided by additional energy used by the system, such as gas or electric energy.  The higher the SEF, the more energy efficient the solar water heating system.  SEF ranges from 1 to 11 with 2 or 3 SEF being the most common.  Solar Fraction on the other hand is another solar performance metric which is the portion of a conventional water heating load.  A higher solar fraction means the more energy the solar heating system contribute to the overall heating of the water, thus, reducing the energy needed by the backup water heater.  SF ranges from 0.0 to 1.0 with 0.5 and 0.75 SF being the most common.
  • Storage Water Heaters – when it comes to determining the energy efficiency of a storage water heater, they Energy Factor (EF) ratings.  In fact, EF is not just used for rating storage water heaters, but it is also used in determining the energy efficiency of tankless water heaters and heat pump water heaters.  The EF in these types of water heaters the overall efficiency of the water heating unit based on how much hot water was produced per unit of fuel.  Overall, when a water heater unit has a high energy factor, the more energy efficient it is.  However, this does not always translate to lower operating cost, especially if the type of fuel you use is more costly than others.  How it is measured will include the following:
  1. Recovery Efficiency – this is a calculation of how efficiently the heat coming from the heat source can be transferred to the water.
  2. Standby Loss – this is a calculation of how much heat is lost per hour when heated water is stored (used for units with storage tanks).
  3. Cycling Loss – this is a calculation of how much heat is lost as the water moves about the tank to the outlet pipes.
  • Tankless Coil these water heating units uses heating coils or heat exchangers installed on a furnace or boiler.  When a tap is turned on, water flows through the heat exchangers.  They work in a similar way to tankless water heaters, only they rely on a furnace to heat the water directly.  Since furnaces and boilers are not turned on during the warm months, it means they will not be able to provide you with heated water.  This makes them inefficient, especially for homes in warmer climates or encounter warm climate.

Cost – this too is a crucial criterion as it provides you with an upfront idea on operating cost.  Before purchasing a water heater unit, it is essential to know, even at least an estimate, the annual operating cost of the unit.  Knowing this will allow you to compare annual operating cost of other similar units.  In fact, this can also help you determine how much energy savings you get from an energy efficient model.  Their only drawback though is that they have a much higher purchase price.  Nevertheless, the added price will be offset by the saving you get on your utility bills.  The list below shows the types of water heater units and an estimated calculation of their annual operating cost.

  • Storage, Tankless, and Heat Pump Water Heater – the annual estimated operating cost for these units is computed by calculating the energy factor (EF) of the unit, the type of fuel it uses and its cost, and the amount of water beings used; roughly 64.3 gallons per day, the average usage of a household with three people.
  • Solar Water Heater – the annual estimated cost for a solar water heater is computed by calculating its solar energy factor (SEF) along with the fuel type it uses for backup and its cost.

One good way in further reducing the annual operating cost of your water heater is by ensuring your unit does not lose too much heat during standby.  This can be accomplished by further insulating the tank of your unit.  It is also a good idea to insulate some of the exposed hot water plumbing so there is less heat being lost when water travels from your water heater unit to your tap.  Of course, the best way to save money is still to not waste hot water at all.  When using the hot water tap, it is best to turn it off when you are not washing anything, even if it is just a few seconds.  This method will help to save you a lot of energy.



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