Water Heater First Hour Ratings: What You Need to Know

by Jessica Sawyer | Water Heaters

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Whether you’re looking for something new or are just trying to get a better understanding of your current model, understanding a water heater’s First Hour Rating (FHR) is crucial for assessing its overall performance. However, it can be difficult to figure out exactly what this means by its name alone, let alone why you should care. So, you may be wondering: what exactly is a First Hour Rating for a water heater, and why should I be paying attention to it?

In this blog post, we’ll guide you through everything you need to know about First Hour Ratings. We’ll talk about what they are and why they matter, how to calculate them, and give you some tips on how to improve your water heater’s First Hour Rating to help it meet your home’s specific needs.

What Is a Water Heater’s First Hour Rating, and Why Should I Care?

First things first – what exactly are we talking about here? Well, the First Hour Rating (FHR) refers to the amount of hot water your water heater can supply in its first hour of operation when it’s fully heated. It’s measured in gallons, and provides a clear snapshot of how effectively a water heater can meet your household’s peak hot water demands.

Of course, as a homeowner, you want to ensure that your water heater can meet your family’s hot water needs. This is especially during peak usage times, such as mornings when multiple showers might be taken back-to-back (unless you’re lucky enough to have a cold shower-lover in your household!). So, by paying attention to the FHR of a water heater, you can ensure that it will deliver a steady supply of hot water when you need it most.

Really, having a water heater with an FHR that’s appropriate for your household can mean the difference between a warm, relaxing shower and an unexpected cold blast. Even better, it helps in energy conservation, as it prevents the heater from continuously working throughout the day to meet demands it wasn’t sized appropriately for.

What Factors Affect the First Hour Rating of a Water Heater?

The FHR of a water heater isn’t just a standard number. Several factors can affect it, including:

a. Tank Size

The size of the water heater tank directly impacts its FHR. Larger tanks can hold and heat more water, so they’ll have a higher FHR.

b. Fuel Type

Water heaters can be powered by electricity, gas, or other fuels, and this can affect their First Hour Rating. Now this isn’t always true, but generally speaking, gas water heaters have higher FHRs compared to electric ones due to their quicker heating capabilities.

c. Heating Elements

The efficiency and number of heating elements also play a role in FHR. For example, more efficient elements can heat water more quickly, increasing the FHR.

d. Temperature Rise

This is the difference between the input water temperature and the desired output temperature. A higher temperature rise means the heater has to work harder, affecting the FHR.

How to Calculate Your Household’s First Hour Rating

To determine the appropriate FHR for your home, you’ll want to calculate your household’s peak hour demand within a few gallons. Here’s a simple way to do it:

Step 1: Identify Peak Hour Activities

The first step in calculating the First Hour Rating of a water heater is to list all the activities that require hot water during your home’s busiest hour. Common activities include:

  • Showers
  • Running the dishwasher
  • Washing clothes
  • Hand washing

Step 2: Estimate Hot Water Usage

Once you have your list of peak activities, it’s time to estimate the gallons of hot water used by each one. Now, we realize that it can be difficult to come up with these numbers – how are you supposed to measure the amount of water pouring out of the showerhead?

If you’re looking to make the process a little easier, here are some some average guidelines for you to work with:

  • Shower: 10 gallons
  • Dishwasher: 6 gallons
  • Washing dishes by hand: 4 gallons
  • Clothes Washer: 7 gallons per load
  • Hand Washing: 1 gallon per use

Step 3: Add Up the Totals

Fortunately, the math involved with calculating a water heater’s First Hour Rating isn’t too complicated. You just need to add up the estimated gallons of hot water used during peak hour activities. 

For example, if you have two showers, one dishwasher load, and three hand washes in one hour, the total would be:

(2 showers x 10 gallons) + 6 gallons for dishwasher + (3 hand washes x 1 gallon) = 29 gallons.

In this case, you’d need a water heater with an FHR of at least 29 gallons.

Tips for Improving a Water Heater’s First Hour Rating

So, how’d the calculation work out? Is your water heater’s FHR rating not quite meeting your needs? Well, whether you’re looking to make the most out of your current model or are planning to buy one, there are a few things to do to improve or maximize a water heater’s FHR:

Regular Maintenance

Regularly maintaining your water heater by flushing the tank and checking for sediment build-up can improve efficiency and potentially boost its First Hour Rating. For best results, consider booking an annual maintenance appointment with a qualified plumber.

Insulate Your Water Heater

Insulating your tank helps in retaining heat, which can improve the efficiency of your water heater.

Upgrade Heating Elements

Consider upgrading to more efficient heating elements if your current ones are underperforming.

Optimize Usage Patterns

You may need to juggle some things around, but consider optimizing your household’s hot water usage patterns so you’re not trying to use it all at the same time. This may mean spreading out activities like washing clothes and showering over different periods.

Install a Tankless Water Heater

If your hot water demand is particularly high, you might consider a tankless water heater, which provides hot water on demand and doesn’t rely on a storage tank.

Final Thoughts

Understanding First Hour Ratings is vital for any homeowner looking to make an informed decision about their water heater. By knowing what FHR is, how to calculate it, and why it matters, you can ensure that your home always has a reliable supply of hot water to meet your family’s needs.

Remember, the right water heater not only enhances comfort, but also contributes to energy efficiency and cost savings. So, take the time to analyze your household’s hot water demands, and make sure your water heater aligns with those needs.

And if it doesn’t, we’re here to help! Whether you’re looking to install a new water heater or perform maintenance on your current one, we’ve got you covered. Click here to schedule a Water Pros Plumber online, or call (480) 459-4424 today.

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