Water Heater Sizing: The First Step Toward Peak Performance

Households across America rely on a steady supply of hot water for basic comfort, safety and sanitation. To ensure the best performance from a new or replacement system, make sure you have conducted a proper water heater sizing.


Water heater sizing refers to finding and installing a water heating system that can produce enough hot water to meet your household's demands for hot water. Proper water heater sizing requires consideration of two primary factors:

  • First hour rating: First hour rating is the number of gallons of hot water the heater can provide each hour, starting from a tank full of hot water. The first hour rating of your water heater should be large enough to meet your household's highest level of demand for hot water. When choosing a water heater, check the unit's EnergyGuide label for details on the unit's first hour rating.
  • Peak hour demand: The hot water heater you choose should be large enough to supply hot water to meet your household's peak hour demand, which is the amount of hot water needed during the hour when your home's occupants are using the most of it. Determine your peak hour demand by adding up the number of gallons of water used during the hour when your family is consuming the most hot water for bathing, cooking, cleaning and other tasks. This is often during the morning when everyone is having breakfast and getting ready for work or school. A water heater should have a first hour rating within one or two gallons of your home's peak hour demand.

In general, a 50- to 60-gallon water heater is enough for a home with one to three people. A heater with an 80-gallon storage tank is best for the needs of four people or more.

Customers in the Mid-Ohio area can rely on Joe Behr Plumbing and Heating, Inc. for fast, reliable HVAC services and solutions to plumbing problems. Contact us today for more information on water heater sizing or for expert assistance choosing a new water heating system that will easily meet your household demand for hot water.

Our goal is to help educate our customers in the Mid-Ohio area about energy and home comfort issues (specific to HVAC systems).  For more information about water heater sizing and other HVAC topics, visit our website.

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