Choosing the Right Size Water Heater - What Size of Water Heater Do You Need?

4 May 2015
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No one wants to take a cold shower or have high energy costs. Learn how to pick a water heater that will provide your family with reliable hot water for years to come.
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No one wants to take a cold shower or have high energy costs. Learn how to pick a water heater that will provide your family with reliable hot water for years to come. A properly sized water heater will meet your household's hot water needs while operating more efficiently. Therefore, before purchasing a water heater, make sure it's the correct size.

The good news is that just by following a few guidelines, you can find the perfect size water heater

Sizing Your Water Heater
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A number of factors affect water usage in a home and sizing is the technique that takes these factors into consideration and matches the needs with the size of the water tank.

Now for tank water heaters, one of the key factors is the hot water storage capacity. Other important factors include:

  •    the number and age of of family members
  •    quality and type of water fixtures
  •    peak usage which can be determined by family size and lifestyle (vistors, baths versus showers etc)
Do a Lifestyle Audit
SHOWER HEAD

Rheem recommend that  you should start with a lifestyle audit of your typical usage:

  • How many people are showering and when? Is there a "shower rush hour" in the morning or night?
  • Do they have a deep soaking tub or whirlpool? What is its fill capacity in gallons? And how do they use their tub; e.g. do they take a long shower first and then get into a full tub?
  • When are major appliances in use? Are the dishwasher and washing machine needed at the same time family members are showering?.
  • How much hot water is needed to deliver the experience you want in your bathroom? For example, is there enough hot water to fill a deep soaking whirlpool or to operate a vertical spa-type shower for any length of time?

Establish peak demand, measured in gallons per hour (gph). Then evaluate tank water heaters on the same gph basis to determine how many gallons of storage are needed to meet this demand.

Sample Calculation
Calculator Icon

The worksheet example shows a total peak hour demand of 36 gallons. Therefore, this household would need a water heater model with a first hour rating of 34 to 38 gallons.

Worksheet for Estimating Peak Hour Demand/First Hour Rating *

Use

Average gallons of hot water per usage

 

Times used during 1 hour

 

Gallons used in 1 hour

Shower

10

×

 

=

 

Shaving (.05 gallon per minute)

2

×

 

=

 

Hand dishwashing or food prep (2 gallons per minute)

4

×

 

=

 

Automatic dishwasher

6

×

 

=

 

Clothes washer

7

×

 

=

 

 

 

 

Total Peak Hour Demand

=

 

 

EXAMPLE

3 showers

10

×

3

=

30

1 shave

2

×

1

=

2

1 hand dishwashing

4

×

1

=

4

Peak Hour Demand

 

 

 

=

36

Adapted from information from the Federal Energy Management Program Energy Cost Calculator
*The above worksheet is based on standard usage with no water conservation measures.

Read More on Steamy Showers with Rheem Water HeatersChoosing the right size water heater

The Trinidad Distributer of Rheem Water Heaters is Electricial Industries Group Limited (EIG)

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EIG Limited is the Distributor of Rheem Water Heaters
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