What Is Water Heater First-Hour Rating (FHR)?

There are many technical terms you need to be familiar with when installing a water heater in your home. This is important to safely use the heater and care for it. The first-hour rating (FHR) of a water heater is one such term you need to understand. Even though water heater brands advertise many great features of their products, the FHR or the amount of water the heater can produce within one hour is one of the most important features to consider when investing in a quality water heater for your home. This article explains what the first-hour rating (FHR) of a water heater is all about.

Key Takeaways

• The first-hour rating (FHR) indicates the amount of water a heater can produce within one hour, making it a crucial feature to consider when purchasing a water heater.
• FHR is calculated by multiplying the heater’s maximum capacity by 70% and adding the recovery rate, reflecting the heater’s ability to deliver hot water during peak usage.
• Choosing the right FHR for your home is essential, based on the household’s hot water consumption during peak hours, ensuring a consistent hot water supply.

What Is The FHR Of A Water Heater?

The FHR is the capacity of a water heater to deliver 100% heated water within the first hour of its operation. The maximum capacity and the recovery rate of the heater comes to play in this regard. It’s mandatory for every manufacturer to provide the FHR label on the water heater. In order to get the first-hour rating of a water heater, you should multiply the maximum capacity by 0.70 (70%) and add it to the recovery rate of the heater. The total is the FHR measured by gallons per hour. The 70% is the amount of hot water the heater is capable of delivering on peak hour.

You may wonder why only 70% of the maximum capacity of the heater is taken for the calculation. You need to know how a typical water heater functions to understand this. When you consume hot water, new cold water will start to enter the tank of the heater. This usually happens from the bottom in order to replace the amount of water lost. The overall temperature will drop as a result of the mix of cold water. The rest of the hot water becomes colder as new cold water enters the tank. Once you have used 70% of the heater’s full capacity of hot water, the remaining water will likely become cold.

A typical heater will start to heat water as the hot water in the tank goes out and the cold water comes in. Based on the set temperature level, the thermostat of the heater will sense the loss of heat in the tank. Due to this process, you can expect at least 70% of the water to be at the same temperature that you desire. Most heater brands will allow a 20% drop of temperature from the set point of temperature. For example, if a homeowner sets the heater to warm water at 120 degrees, he or she can expect hot water temperatures that range from 100 to 120 degrees in the 70% amount.

Computing The FHR

The formula for computing the FHR is:

Tank capacity in gallons X 0.70 or 70% + recovery rate = FHR in gph (Gallons per Hour).

For example, the tank capacity is 50 gallons and the recovery rate of the heater is 40 gph. Applying the above formula to this, you will get the following answer.

50 gallons X 0.70 + 40 gph = 75 gph (this is the FHR of the heater).

How To Determine The Right FHR For Your Home

Each family may have their own hot water requirements. You can estimate the use of hot water in your home for various activities during peak hours for this calculation. Peak hour means the times when your family uses hot water. For example, let’s say you have three members in the family (father, mother, and daughter), and you use approximately 74 gallons of hot water per peak hour. With 74 gph of usage, you should opt for a water heater with a first-hour rating of 74 gph or something close to that figure. But if your family uses a lot of hot water each day, you should opt for a water heater with a fast recovery rate. These are important factors to consider when shopping for a quality water heater for your home.

Household water heaters play an important part in your home, especially during the cold season. There are many features to look for when buying a water heater. The first-hour rate or FHR is one of the most important features to consider when investing in a quality water heater for your home.

Case Study: Selecting a Water Heater Based on First-Hour Rating (FHR) for Optimal Performance

Background

A UK-based family of four approached Heat Pump Source to replace their old water heater with a more efficient model. The household experienced frequent shortages of hot water, especially during peak usage times in the morning and evening. The family’s primary concern was ensuring a consistent supply of hot water for showers, dishwashing, and other daily needs.

Project Overview

The objective was to select and install a new water heater with an appropriate first-hour rating (FHR) to meet the family’s hot water demands. Key considerations included understanding the family’s usage patterns, calculating the necessary FHR, and ensuring energy efficiency.

Implementation

Assessment and FHR Calculation

• Usage Analysis: We conducted a detailed analysis of the family’s hot water usage, focusing on peak hours. Activities such as simultaneous showers, dishwashing, and laundry were accounted for to estimate the total hot water requirement.
• FHR Determination: Based on the assessment, we calculated that the family required approximately 80 gallons of hot water during peak usage times. This figure guided our recommendation for the new water heater’s FHR.

System Selection and Installation

1. Choosing the Heater: We recommended a water heater with a first-hour rating of 85 gallons, slightly above the calculated requirement to ensure a buffer for any unexpected high usage. The chosen model also featured a high recovery rate, allowing it to quickly reheat water as it was used.
2. Professional Installation: Our certified technicians installed the new water heater, ensuring proper setup and integration with the existing plumbing system. The installation included testing the system’s functionality and ensuring that the FHR matched the specifications.

Post-Installation Support

• System Testing and Adjustment: After installation, we tested the water heater’s performance during peak usage times. Adjustments were made to the thermostat settings to optimise energy efficiency and ensure consistent water temperature.
• Maintenance Plan: We provided the family with a maintenance plan, including annual inspections and periodic checks of the system’s components. This plan is crucial for maintaining the water heater’s efficiency and prolonging its lifespan.

Results

• Improved Hot Water Availability: The new water heater’s FHR met the family’s demands, eliminating previous issues of running out of hot water during peak times.
• Energy Efficiency: The high FHR and recovery rate of the system ensured efficient operation, reducing energy waste and lowering utility bills.
• Customer Satisfaction: The family was highly satisfied with the consistent availability of hot water and the professional installation process. The system’s energy efficiency also contributed to a noticeable reduction in their monthly energy expenses.

Summary

This case study highlights the importance of selecting a water heater with an appropriate first-hour rating (FHR) based on the specific hot water needs of a household. At Heat Pump Source, our expert analysis and tailored recommendations ensured that the family received a system that not only met their requirements but also operated efficiently. Proper understanding and calculation of FHR, along with professional installation and maintenance, are key to achieving optimal performance and customer satisfaction in water heating solutions.

Expert Insights About Water Heater First-Hour Rating (FHR)

Understanding the first-hour rating (FHR) of a water heater is crucial for ensuring that your home has a consistent supply of hot water, especially during peak usage times. The FHR essentially tells you how much hot water you can expect from your system within the first hour of use, which is vital for planning your household’s hot water needs.

Senior HVAC Engineer

Choosing the right FHR is not just about having enough hot water; it’s also about efficiency and energy savings. A water heater with an appropriately sized FHR can help you avoid unnecessary energy consumption and ensure that your system operates efficiently, even during high-demand periods.

Energy Efficiency Specialist

For families with higher hot water demands, a water heater with a higher FHR is essential. It’s important to consider not just the peak hour usage but also the recovery rate, which affects how quickly the system can heat additional water as it is used.

Technical Consultant

Heat Pump Source: Reliable Heating and Cooling Solutions

At Heat Pump Source, we take pride in our unwavering commitment to serving the UK with top-tier HVAC solutions. From the efficiency of heat pumps and the cool relief of air conditioning to the warmth of boilers, radiators, and underfloor heating, our dedicated team is always at the forefront of innovation. We understand the unique needs of every household and business, and we strive to provide dependable health and cooling products and services that are tailored just for you. Ensuring your comfort and satisfaction is our utmost priority. Whether you have questions, need guidance, or require support, we’re always here to assist. Please don’t hesitate to contact us; we’re eager to be of service.

Conclusion

Understanding a water heater’s first-hour rating (FHR) is paramount for homeowners investing in a reliable and efficient water heating system. The FHR provides insight into the heater’s performance during peak usage and aids in making an informed decision tailored to the household’s specific hot water needs. As with any significant home appliance purchase, being equipped with the right knowledge ensures that you get the best value for your investment and consistent comfort for your family.