What Size Tankless Water Heater To Replace A 50 Gallon?

To replace a 50-gallon tank, consider a tankless water heater with a flow rate of at least 5 gallons per minute. A tankless water heater with a flow rate of 5 gallons per minute or higher is typically sufficient to replace a 50-gallon tank and meet the hot water needs of a household.

With advancements in technology, tankless water heaters have become a popular alternative to traditional water tanks. These compact and efficient units offer endless hot water supply while minimizing energy consumption. If you are considering replacing your 50-gallon tank, it is important to choose the right size tankless water heater to ensure adequate hot water supply for your household’s needs.

We will explore the ideal tankless water heater size to replace a 50-gallon tank while maximizing efficiency and convenience. By understanding the key factors and considerations, you can make an informed decision and enjoy the benefits of a tankless water heater in your home.

What Size Tankless Water Heater To Replace A 50 Gallon?

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Factors To Consider When Replacing A 50 Gallon Water Heater

Are you looking to replace your old 50-gallon water heater with a more efficient tankless option? Before making your decision, it’s important to consider a few factors that will help you determine the right size tankless water heater for your needs.

Let’s take a closer look at these factors:

Existing Water Usage

Understanding your current water usage patterns is crucial in determining the appropriate size tankless water heater. Consider the following points:

  • Take note of the daily hot water usage in your household. How often do you use hot water for showers, dishes, laundry, and other activities? A rough estimate will help determine the capacity you require.
  • Analyze the peak demand periods, particularly when multiple hot water outlets are in use simultaneously. This will help you gauge the flow rate required for your tankless water heater.
  • Consider any planned changes in your household, such as additional family members, renovations, or the addition of new appliances that may affect your hot water demand.

Number Of Bathrooms

The number of bathrooms in your home directly influences the hot water demand. Here’s what you need to know:

  • Each bathroom typically requires a specific flow rate of hot water. For instance, a standard showerhead delivers around 2.5 gallons per minute (gpm), while a bathtub faucet can reach up to 5 gpm.
  • Calculate the combined flow rate of all the hot water fixtures that may be in use simultaneously in your bathrooms. This will determine the minimum flow rate your tankless water heater should handle.
  • Consider any future plans for additional bathrooms or the conversion of existing spaces, as these changes will impact the hot water demand and should be accounted for when selecting the tankless water heater size.
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Desired Hot Water Flow Rate

The hot water flow rate refers to the speed at which hot water is delivered by the tankless water heater. Consider the following factors when determining the desired flow rate:

  • Evaluate your hot water needs and lifestyle preferences. Do you prefer a strong, high-pressure flow or are you content with a gentle, low-pressure stream?
  • Certain appliances, such as a large soaking tub or a spa shower system, require a higher flow rate to meet your desired experience. Ensure that your tankless water heater can accommodate these demands.
  • Consider the specific flow rate recommendations provided by the manufacturer for various fixtures and appliances. This will help you select a tankless water heater that can deliver the required flow rate consistently.

By taking into account your existing water usage, the number of bathrooms, and your desired hot water flow rate, you can make an informed decision on the appropriate size tankless water heater to replace your 50-gallon unit. Remember to consult with professionals and carefully review the specifications of different models to ensure the best fit for your household’s needs.

Calculating The Required Size Of Tankless Water Heater

Are you considering replacing your 50-gallon water heater with a tankless option but unsure about the right size to choose? Selecting the appropriate size tankless water heater is crucial to ensure that you meet your peak hot water demand without any hiccups.

In this section, we will guide you through the process of calculating the required size for your tankless water heater.

Determine Peak Hot Water Demand

Before you can determine the size of your new tankless water heater, you need to understand your peak hot water demand. This refers to the maximum amount of hot water you and your household require at any given time. To determine this, consider the following factors:

  • Number of people in your household and their hot water usage habits.
  • Appliances that use hot water, such as showers, dishwashers, and washing machines.
  • Duration and frequency of hot water use during peak periods, such as mornings or evenings.

Calculate Required Flow Rate

Once you have an idea of your peak hot water demand, the next step is to calculate the required flow rate for your tankless water heater. Flow rate refers to the amount of hot water required per minute. To calculate this, consider the following:

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  • Determine the total flow rate of all hot water outlets that may run simultaneously, such as showers or faucets. Add up their individual flow rates.
  • Multiply the total flow rate by 0.75 to account for the hot water temperature rise. This will ensure you have sufficient hot water even when the incoming water is colder during winter months.

Select The Appropriate Size Based On Flow Rate

Now that you have the required flow rate, you can select the appropriate size of tankless water heater to meet your needs. Tankless water heaters are typically measured by the gallons per minute (gpm) they can provide. Consider the following points during selection:

  • Look for tankless water heaters with a gpm rating that matches or exceeds your required flow rate.
  • Keep in mind that selecting a slightly higher gpm rating can provide more flexibility and accommodate potential future changes in your household’s hot water demands.
  • Consult with a professional plumber if you are unsure about the right size or if you have specific requirements that require expert advice.

By determining your peak hot water demand, calculating the required flow rate, and selecting an appropriate size tankless water heater, you can ensure a seamless transition to a more energy-efficient and convenient hot water solution for your home. Remember to follow manufacturer guidelines and seek professional assistance when necessary to make the best decision for your specific needs.

Benefits Of Upgrading To A Tankless Water Heater

Energy Efficiency And Cost Savings

Upgrading to a tankless water heater can bring numerous benefits, including improved energy efficiency and cost savings. Here are some key points to consider:

  • Tankless water heaters are designed to heat water on demand, avoiding the need for a large storage tank and the energy required to keep that water constantly heated. This on-demand heating system can result in significant energy savings.
  • Traditional tank-style water heaters continually heat and reheat water in the storage tank, even when it’s not in use. This constant heating process can lead to energy wastage and higher utility bills.
  • By opting for a tankless water heater, you can effectively eliminate standby heat loss, where energy is wasted by keeping a large volume of water hot.
  • As tankless water heaters provide hot water only when you need it, there is no need to continuously maintain a large volume of heated water. This can lead to substantial savings on your energy bills.

Space-Saving Design

Another advantage of upgrading to a tankless water heater is the space-saving design. Here’s why it matters:

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  • Tankless water heaters are compact and wall-mounted, occupying much less space compared to traditional tank-style water heaters. This can be especially beneficial for homeowners with limited space in their utility rooms or homes.
  • Traditional tank-style water heaters can be bulky and require a significant amount of floor space. In contrast, tankless water heaters can free up valuable space in your home for other purposes.
  • The compact design of tankless water heaters also allows for flexibility in installation. They can be placed in various locations, such as under sinks, closets, or even outside the house, depending on the model and your specific needs.

Continuous Hot Water Supply

One of the most remarkable features of tankless water heaters is their ability to provide a continuous supply of hot water. Consider the following:

  • With a tankless water heater, you’ll never have to worry about running out of hot water during long showers or when multiple appliances are in use at the same time.
  • Tankless water heaters heat water as it passes through the unit, ensuring a constant supply of hot water whenever you need it, without any delays or interruptions.
  • This continuous hot water supply can be particularly advantageous for larger households or families, where hot water demand tends to be higher.
  • Additionally, tankless water heaters can deliver an endless stream of hot water, making them suitable for activities like filling up a hot tub or running a large capacity washing machine.

Upgrade to a tankless water heater and enjoy the benefits of energy efficiency, cost savings, space-saving design, and a continuous hot water supply. With these advantages, it’s clear why more homeowners are opting for tankless water heaters as a replacement for their 50-gallon tanks.


Based on the information presented, it is clear that choosing the right size tankless water heater to replace a 50-gallon tank is a crucial decision. By considering factors such as demand, temperature rise, and flow rate, you can ensure that your new tankless heater will meet your household’s hot water needs efficiently.

Remember to consult with a professional to calculate the specific requirements for your home and make an informed decision. Investing in a tankless water heater not only saves space but also offers energy-efficiency benefits and long-term cost savings. With a well-chosen tankless water heater, you can enjoy endless hot water without the limitations of a traditional tank.

So, take the time to research, evaluate your needs, and make the right choice for a reliable and efficient hot water solution.


I am a mechanical engineer and love doing research on different home and outdoor heating options. When I am not working, I love spending time with my family and friends. I also enjoy blogging about my findings and helping others to find the best heating options for their needs.