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How do I size a water heater?

bean Member Posts: 34
Looking for some help sizing a domestic water heater.(electric). Any Help?


  • Larry Weingarten
    Larry Weingarten Member Posts: 3,289
    Hi, There are various methods. Do you know how many people the heater will serve, or how many bedrooms? Single family or multi family? B)
    Yours, Larry
  • Zman
    Zman Member Posts: 7,569
    Electrics are pretty simple because you have very little choice on input power. Most are 4.5-5.5 KW (5 KW x 3,412 + 17,060 BTU/Hrs.) From there, you look at your demand and decide how much storage you need. If you have lot's of shower going at the same time, or large tubs to refill, you will want to go big.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Intplm.
    Intplm. Member Posts: 1,945
    The simplest and most general rule is as follows for a tank water heater:

    1-2 people in the house hold 30-40 gallon
    2-4 people 40-50 gal.
    3-4 people 50-60 gal.
    5-6+people 60-80 gal.
    If you have any of the amount of people listed above but use more than one washing machine or dishwasher, you should round up to the next size water heater.
    Again this is for the use of a tank water heater.

    You can figure this more accurately if you like by adding up the gallons per. minute used at each hot water fixture and appliance, but most often you will still come up with the above results.
    EBEBRATT-Ed Member Posts: 15,517
    common sense + Some of the water heater manufacturers have calculators on their web site. I know State water heater has one
  • Big Ed_4
    Big Ed_4 Member Posts: 2,783
    Take a shower , measure you flow rate of shower head . 5gallon bucket and a stop watch . 1.5 , 2 or 5 gallons a minute ... Length of shower wanted x flow rate will equal the size of the tank needed ....
    I have enough experience to know , that I dont know it all
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,289
    Hello, Following on what @Big Ed_4 just said, install a low flow head and then you might be able to put in a smaller place heater. That shower head pays for itself instantly! :p
    Yours, Larry
  • ProblemSolver
    ProblemSolver Member Posts: 190
    one of the big pluses with electric is to have 2 heating elements, not 1. Another suggestion, the main reason a hot water tank's life gets shortened is because of running it out of hot water. With that great temperature change at the point of no hot water left, the steal and glass expands at different rates, thus causing the glass to crack and the rusting process on the steal begins. During a shower, to help lower the rate of hot water used I have a shut-off valve behind the shower head and I greatly reduce the flow while washing and increase it to rinse. And if you're using city water, most likely it has chlorine in it. So use a shower filter to remove the chlorine and your skin and hair will start to feel healthier. When absorbed, chlorine temporarily interferes with the absorption of oxygen at the cellular level.
    Good luck...
  • bob eck
    bob eck Member Posts: 930
    50 gallon electric water heaters cost less than 30 and 40 gallon models.
    Use 1.5 GPM shower heads.
    Use low flow aerators in the faucets.
    Install a water heater mixing valve and store the water at a higher temp and mix it down to 120 F going out to the faucets.
    We stock a HTP 80 gallon light commercial water heater.