Gas Water Heater Sizing Guide

To select the right A.O. Smith water heater for your home, you need to consider the size of your family and other factors that contribute to your First Hour Rating Requirement. The chart below provides A.O. Smith Residential Gas Water Heater sizing guidelines for several family sizes.

To Choose the Right Water Heater for You...

1. Determine whether your family is Low Demand or High Demand. You should consider your family to be High Demand if...
   • There are more than two full baths in the home.
   • There are (or will be) teenagers living in the home. It's a fact: teenagers use more hot water for showering and washing clothes.
   • If you have an oversized whirlpool bath or other large tub. As a rule of thumb, the water heater tank capacity should be 100% of your bathtub capacity (example: 75-gallon tub / 75-gallon water heater).
2. Find your Family Size and Demand Profile in the chart below, and read across to find the First Hour Rating Requirement for your family. If you decide your family is High Demand, consider moving up to the next First Hour Rating level.
3. Consult the charts on respective water heater specifications for an A.O. Smith residential gas water heater with a First Hour Rating that meets your requirement.

FAMILY SIZE	FIRST HOUR RATING REQUIREMENT
2 People	45 - 55 Gallons
3 People	55 - 65 Gallons
4 People	65 - 75 Gallons
5 People	75 - 85 Gallons
6 People	85 - 100 Gallons
7 or More People	100 or More Gallons

Remember, these are general recommendations...your A.O. Smith Water Heater Specialist can review your family's needs in even greater detail to make sure the model you choose will always provide enough hot water to meet the demand.

Code Compliance: A.O. Smith residential gas water heaters comply with the following standards: HUD, ASHRAE/IES 90.1b-1992 and 1990 NAECA. All models design-certified by CSA International to ANSI standards for residential water heaters.

Information Source: A.O. Smith