What Size Of Tankless Water Heater Do I Need – The Truth Reveals

Installing a tankless water heater in your house can be quite beneficial, drastically reducing your energy bills and allowing you to enjoy hot water on demand. However, with so many sizes, features, and options available on the market today it can also be overwhelming, after all, how do you know what size of tankless water heater is right for you and your family’s needs? That’s why we’ve created this guide, to help make it easier for you to find the perfect tankless water heater size! Whether you have a small or large home, or simply want an energy-efficient upgrade from a traditional model, there are plenty of options out there to choose from. Let’s get into it and talk about what size of tankless water heater I need that will work best.

Let’s explore what size of tankless water heater do I need.

Your home’s need for hot water, the type of tankless water heater you select, the number of bathrooms in your house, and other considerations will all affect the amount of tankless water heater you need. Take into account the following factors to help you choose the ideal tankless water heater size for your home:

1: Type of Tankless Water Heater:

The type of unit you select will determine the size of the tankless water heater you require. For example, an electric tankless water heater requires a larger capacity than a gas-fired tankless model to meet your home’s hot water needs and demands.

2: Home’s Hot Water Needs and Demand:

The size of the tankless water heater you need is directly related to your home’s hot water needs and demand. To determine the amount of hot water needed, consider how many people will be using hot water at once and for what types of uses (e.g., showers, laundry, etc.).

3: Number of Bathrooms:

Another aspect to take into account when choosing the size of a tankless water heater is the number of bathrooms in a house. Generally, one bathroom requires approximately 3 gallons per minute (GPM) of hot water flow and each additional bathroom requires 1 GPM more.

4: Size of Home:

The size of your home is also a factor to consider when determining the size of the tankless water heater needed. Generally, larger homes require more hot water flow and demand than smaller homes.

By considering these points, you can determine the type and size of tankless water heater that best meets your home’s needs and hot water demand. However, the average house with 2-3 bathrooms and located in a moderate climate such as California or Washington typically requires a mid-sized tankless water heater with a capacity of around 199,000 BTUs. If you live in an area with cold winters or if your house has more than 3 bathrooms, it is suggested to opt for a larger unit that can provide up to 399,000 BTUs.

Additionally, if you have several high-demand appliances such as dishwashers or washing machines that require hot water, then you may need to choose a higher capacity unit even if your household size is small. Installing two smaller units instead of one large one can also be beneficial since it allows for better energy efficiency and cost-effectiveness and will allow you to adjust the amount of hot water depending on your needs at any given time. Before selecting any tankless water heater, make sure to consider all factors such as demand levels, local weather conditions, and house size to ensure that you get the most efficient size for your specific usage requirements.

Factors to Consider When Determining Tankless Water Heater Size 

It’s crucial to take these aspects into account when choosing the size of a tankless water heater to decide the exact size that will meet your needs.

1: Hot Water Needs

When determining the size of the tankless water heater required and selecting an appropriate unit, it is important to consider the total hot water needs of a building or home. This requires factoring in the number of occupants, as well as any individual habits regarding baths and showers, such as how often and for how long they are taken. Additionally, any large appliances that require hot water need to be taken into account, such as dishwashers and washing machines. It should also be considered if multiple hot-water-using applications are running at the same time; will their combined demand exceed what a single tankless water heater can provide?

2: Fixture Flow Rates

The flow rate of fixtures in a home or business can affect what size tankless water heater would be necessary. The gallons per minute (GPM) rating at which hot water flows from each fixture is referred to as the flow rate. Knowing these rates is important for accurately estimating how much hot water will be used at any given time from all sources to make sure that the selected tankless water heater has enough capacity.

Here is a helpful table showing the GPM requirements for various water fixtures:

Fixture	Average Flow GPM
Bathroom Sink	1 GPM
Bathroom Shower	2 GPM
Kitchen Sink	1.5 GPM
Kitchen Dishwasher	2 GPM
Washing Machine	2 GPM

3: Temperature Rise 

Temperature rise is about how much hotter the supplied hot water should be than incoming cold water. While many tankless units are advertised with temperature rise ratings up to 45 degrees Fahrenheit, it is important to consider that higher temperatures require more energy and will reduce efficiency over time if not kept at sensible levels. Selecting an appropriately sized heater with enough power and capacity to meet the temperature rise requirements without unnecessary output is key for achieving optimal cost savings in energy usage over time. 

4: Location of Heater Unit 

In some instances, where space requirements dictate or other limiting factors exist about the location of installation such as ventilation concerns or proximity to other utilities or appliances, there may be constraints on what size tankless unit can be installed in a particular area or region.  

How to Calculate the Right Size of a Tankless Water Heater

1: Calculate Temperature Rise

When it comes to tankless water heaters, the first step in determining the correct size is to calculate the temperature rise. To achieve this, take the target hot water temperature and subtract the incoming cold water temperature. The temperature increase that results will show you what size tankless water heater you need to buy.

For instance, if the temperature of your incoming cold water is 50 degrees Fahrenheit and you want the temperature of your hot water to be 120 degrees Fahrenheit, you will need a temperature rise of 70 degrees Fahrenheit.

2: Determine Peak Hot Water Demand 

The second factor that needs to be considered when calculating the right size of a tankless water heater is peak hot water demand. This refers to how much hot water will be used at any given time during peak periods of usage in a household. It’s important to determine this number as selecting an undersized unit can result in insufficient hot water production and can lead to lukewarm or even cold showers on busy days.

To accurately estimate peak hot water demand, it’s best to consider the total number of fixtures in your home that require hot water e.g., faucets, showers, and dishwashers. Also, take into consideration how many family members are living in your home. Knowing your peak hot water demand will help you choose a tankless model with enough power and capacity to meet your needs without wasting energy on unnecessary features or overspending on larger models than necessary.

For Instance:

Let’s say that you have three showers, two faucets, and one dishwasher in your home and four family members. To calculate the peak hot water demand for this scenario, you would add up the flow rate of each fixture:

Showers = 2 GPM

Faucets = 1 GPM

Dishwasher = 2 GPM

Total = 5 GPM.

To fulfill your home’s peak hot water demand, you would require a tankless water heater with a minimum flow rate of 5 GPM.

You can quickly determine the size of the tankless water heater you require by just these two variables: temperature rise and peak hot water demand.

3: Decide On a Tankless Water Heater

Customers can use calculation tables or online calculators provided by tankless water heater manufacturers to help them choose a model based on peak hot water demand and local temperature rise.

For instance,

If the temperature in your area rises by 70 degrees, your residence can have a peak hot water demand of 5 GPM. This may direct your attention to a few models that meet these criteria.

However, the manufacturer can suggest entirely new models if the temperature increase reaches 50 degrees. You should think about alternative tankless heater models if the temperature rise remains constant but the rate of use changes.

Available Tankless Water Heater Models & Sizes  

Once you have calculated the tankless water heater size based on your home’s temperature rise and hot water demand, you can start looking at tankless water heater models and sizes. Tankless water heaters come in various sizes, ranging from compact wall-mounted units to floor-standing models that can deliver large amounts of hot water with minimal energy use. Here are some models of tankless units:

1: Electric Tankless Water Heaters 

Electric tankless water heaters range from 3 to 12 gallons per minute (GPM), with the 4 – 6 GPM range being the most popular size for residential tankless water heater units.

2: Gas-Fired Tankless Water Heaters

Gas-fired tankless water heaters are typically larger than electric tankless water heaters and range in size from 6 to 10 GPM. These models are the most popular tankless unit sizes for commercial applications.

Below is a breakdown of tankless water heater sizes and their corresponding hot water output, to give you an idea of what type of tankless model would work best for your home:

• Small tankless units (6–8 GPM): Ideal for small households, apartments, and condos with 1-2 bathrooms.
• Medium tankless units (8–11 GPM): These tankless water heaters are suitable for small to mid-sized homes with 1-3 bathrooms.
• Large tankless units (11+ GPM): Recommended for larger households that have 2 or more bathrooms and multiple hot water fixtures.

Frequently Asked Questions

Conclusion

We hope you have found this article helpful in answering the question: what size of tankless water heater do I need? Choosing the ideal tankless water heater for your house might be challenging. You’ll need to consider the peak hot water demand and temperature rise in your area, as well as the number of bathrooms and hot water fixtures in your home. Additionally, you may want to use tankless water heater size calculators to help determine which tankless model is best suited for your needs. With the right tankless unit size, you can enjoy endless hot water on demand with greater energy efficiency.