ANSWERS: 1
  • The size of water heater you need depends on the type of water heater you want to buy. Your options include conventional water heaters and demand heaters. Conventional heaters are tanks that hold warm water that is available for immediate use. If your conventional heater is too small, you will eventually run out of hot water. Demand heaters are advantageous because they do not require the water to be stored in the heater so you can reduce your utility bill. If your demand heater is too small, your water will not reach the desired temperature.

    Conventional Heaters

    The size of conventional water heaters are measured by their first-hour rating, which is the amount of hot water that the heater is capable of producing during your busiest hour of the day. To determine the size of the conventional water heater that you need, determine how many gallons of hot water you will use during the busiest hour of the day. According to the U.S. Department of Energy, each shower takes about 12 gallons, washing your hands and face takes about four gallons, automatic dishwasher loads take about 14 gallons and automatic washers take about 32 gallons. Therefore, if you planned to take a shower and run a load of laundry during the busiest hour of the day, you would need a water heater with a capacity of 26 gallons.

    Demand Heaters

    Demand heaters are sized according to their capability of generating hot water virtually instantaneously. Instead of using a first-hour rating, these heaters are measured by their flow rate, or how many gallons of hot water the heater can produce per minute. To calculate the flow rate you need, determine how much hot water you will need at one time by adding the flow rates of the apparatuses that you will be using at the same time. For example, the U.S. Department of Energy suggests that showers use about 2 3/4 gallons per minute and faucets use about 3/4 gallon per minute, so if you planned to have both running at once you would need a demand heater capable of producing 3 1/2 gallons of hot water per minute. To reduce the flow rate of your water, you can install low-flow heads. These will allow you to have a smaller demand heater and to save money on your utility bills.

    Source:

    Conventional Water Heater Sizing

    Demand Heater Sizing

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