The first-hour rating (FHR) is a measure of how much water a traditional water tank is capable of producing through one hour of continuous use. This measure relates to the tank’s capacity and the tank’s recovery rate. For example, if you have a 50-gallon water tank on a gas water heater, you should expect to have a first-hour rating of 70 to 80 gallons. Those with a 50-gallon tank on an electric heater may have a first-hour rating of 60 gallons.

Why Is a First-Hour Rating Important

The first-hour rating of a water tank can tell you if the tank is working as expected. This FHR also helps you determine if your current water tank, or maybe a water tank you are considering purchasing, can keep up with the daily water demand of your household. Different sized water tanks, as well as tanks heated by different energy sources, all have different first-hour ratings.

To determine if your water tank can keep up with your family’s demands, you should calculate your hot water usage during your household’s peak hours. The peak hour or hours would be the time throughout the day when your family uses the most water. Taking a shower or bath typically uses 20 gallons of water per one shower/bath, and running the dishwasher uses around 14 gallons per cycle. If you wash your clothes using hot or warm water, running one load through the washer will use around 32 gallons.

Add up all the peak hour activities that use hot water and compare the gallons used to your tank’s FHR. If the FHR is lower than your demand, it may be time to consider purchasing a new water heater.

What to Do if It’s Time to Purchase a New Tank

If your current water heater can’t keep up with the household demand, it’s time to purchase a larger capacity tank with a higher FHR. At ProMax Water Heaters & Plumbing we service Bellevue, Washington and the surrounding area. Our company offers a variety of plumbing services, including plumbing installations and water heater repair and installation. Contact ProMax Water Heaters & Plumbing for more information.