Choosing the Best-Sized Tankless Water Heater for Your Family

People frequently get confused about the size of the tankless water heater. This is because a tankless water heater that is too small will not be able to meet your need for hot water, and a tankless water heater that is too large will unnecessarily consume more energy, which will result in high utility bills at the end of the billing cycle.

When shopping for a tankless water heater, it is important to consider the unit's capacity. Before we get started analyzing ways to measure the size requirement of the tankless water heater for your home, you need to take into consideration the following two points first.

What is a Tankless Water Heater?

A tankless water heater is a type of water heating system that heats water on demand rather than storing it in a tank for later use. This kind of water heater is also called a demand-type water heater or an instantaneous water heater.

A tankless water heater doesn't store hot water in a large tank. Instead, it uses a heat exchanger to heat water as it passes through the unit, so you always have hot water.

Tankless water heaters that are mounted on the wall are designed to take up less space than their tanked counterparts because they are usually smaller. Although they can be found in a variety of forms and dimensions, the most common ones are either rectangular or cylindrical in outline. They can be controlled via a remote control, control buttons, or a digital display, any of which can be used to make adjustments to the temperature and other settings.

Depending on the model and the types of utilities that are available in the area, some tankless water heaters can be powered by electricity, natural gas, or propane instead of a traditional storage tank.

A tankless water heater has a number of advantages:

Efficient Use of Energy: According to the US Department of Energy, tankless water heaters are 24%–34% more energy-efficient than storage tank water heaters—as long as you use less than 41 gallons per day. Even after doubling that amount, they are still 8%–14% more efficient. Installing a tankless water heater in every location where you need hot water can save you up to 50% on energy. This is a significant improvement over a storage-tank water heater.
It Saves Money: You save money because you use less energy. A tankless water heater will pay for itself in a matter of years, especially if you reside in an area with high energy expenses.
Helps to Save Space: Tankless water heaters are compact because they don't have a storage tank, making them an excellent choice if you want to free up space in your home or have limited space.
Hot Water Availability: Because tankless water heaters heat cold water on demand, you can have hot water eternally as long as the tap is turned on. While there are obvious limits, a tankless water heater may theoretically allow you to enjoy a hot shower for as long as you like without ever becoming chilly.

What to Consider When Purchasing a Tankless Water Heater

Before purchasing a tankless water heater, consider the capacity of the unit as well as the temperature of the water that enters the unit to determine if it is appropriate for your home.

Capacity

The first thing that needs to be taken into consideration is the maximum amount of hot water that will be needed, as well as the capacity of the water heater to heat one minute's worth of water. The amount of heating capacity can be expressed in terms of gallons per minute.

Let's begin by making an estimate of the amount of water that is needed in a household at a particular time. According to research, the hours between 9 p.m. and 11 p.m. are when we use the hottest water. During this time, individuals will clean their teeth, take showers, and operate their dishwashers.

We made a table that lists all of the important water uses that can be measured in GPM. This can help you figure out the size of the tankless water heater you want to buy.

Place/Machines	Gallon Per Minute (GPM)
Kitchen and Bathroom	1.0 to 2.0 GPM
Shower	2.0 to 3.0 GPM
Dishwasher	1.5 to 2.0 GPM
Washing Machine	2.0 to 2.5 GPM

According to this table, if you want to take a bath with water that is 110 degrees Fahrenheit and has a flow rate of 100%, as well as use two faucets at the same time, then you need a tankless water heater in your home that has a minimum capacity of 5 GPM.

In order to meet their daily requirements for hot water, homes typically require between 5 and 10 GPM from their water heaters. When there is a need for up to 8 GPM of hot water, it is recommended that tankless electric water heaters be used.

Consider purchasing a gas tankless water heater if your requirements are more stringent. The price varies depending on the size of the item. The higher the capacity of the water heater, the higher the price of the unit will be.

Inlet Water Temperature

For example, the temperature of the water that is already in the pipeline has a big effect on how much it warms up. Southern Texas has an inlet water temperature of 77 degrees Fahrenheit, while Minnesota has a temperature of 37 degrees Fahrenheit. In order to heat water for your day-to-day activities and responsibilities, your tankless water heater needs to bridge this gap.

What Size Tankless Water Heater do I Need for my Household?

The size of the tankless water heater that should be purchased will be discussed in relation to the number of people living in the household. In general, a family with two or three members requires a unit that is on the smaller side, whereas larger families with four members or more require a tankless water heater that is on the larger side. We will figure out exactly how many GPM and kW are needed to get the effect we want.

How big of a tankless water heater you need depends on the temperature of the water coming in, how much hot water you need, and where your home is. Their requirements are different in the north than they are in the south, which results in different size requirements.

A table of estimates containing a range of GPM and kW has been compiled by us for the family sizes of 2, 3, 4, 5, and 6.

# of People in Household	2 People	3 People	4 People	5 People	6 or More People
Gas Tankless Heater Size (GPM)	6 - 8 GPM	7 - 9 GPM	8 - 10 GPM	9 - 11 GPM	11+ GPM
Electric Tankless Heater Size (kW)	10 - 18 kW	15 - 23 kW	20 - 28 kW	25 - 34 kW	34+ kW

These numbers are only provided here for your convenience. The size of the tankless water heater you need depends on a number of important factors, such as the temperature of the water coming in and how much hot water you need right away.

The question of cost is also an important one to take into account. In order to cover all of the possible scenarios, we will explain them using two different case studies.

Example 1:

What size tankless water heater would be suitable to replace a 50-gallon unit?

You have a water heater that has a capacity of fifty gallons. You will want to get rid of this and get a tankless water heater in its place.

To replace your current 50-gallon water heater, you'll need a tankless gas heater with a minimum flow rate of 10 GPM or a power supply with at least 27 kW in the Northern United States. In the southern United States, you will need a gas tanker that has a capacity of 7 GPM, or 18 kW, of energy.

A good tip is to always buy a tankless water heater that is a little bit bigger than what is estimated, so that you have room for other factors that may come into play.

Example 2:

What size tankless water heater is suitable for a household with five members?

It is likely for a family of five people to make simultaneous use of multiple showers, taps, or faucets. The consumption of water increases proportionately with the population.

A rough estimate says that a family of five in the north of the United States would need about 27 kW of power or 10 GPM of gas tankless heating. Your unit has to work harder to keep the temperature at 110 or 120 degrees Fahrenheit in these situations.

It is possible for consumption to drop by as much as thirty percent in the southern part of the country. You will need a tankless water heater that operates on 7 gallons per minute (GPM) of gas or 18 kW of electrical power.

If you want water to come out of your faucets and showers quickly, you should consider installing tankless water heater circulation pumps to cut down on the amount of wasted hot water.

How Many Tankless Water Heaters are Needed Per Household?

The number of tankless water heaters that an average household needs is going to depend on a few different factors, such as the size of the household, the patterns of how much hot water is used, and the location of the hot water outlets.

Most of the time, a single tankless water heater is enough to meet the hot water needs of a small to medium-sized home. But larger households that use more hot water or homes with more than one bathroom, kitchen, or laundry room may need to have more than one tankless water heater installed.

Also, if the hot water outlets are a long way from the main unit or if the household wants hot water in more than one place at the same time, the household may need to install more than one tankless water heater to make sure that hot water gets to all of the outlets in a timely manner.

It is also important to consider the climate and the incoming water temperature. This is because a tankless water heater may not work as well if the temperature of the water coming in is lower than the desired temperature.

When trying to figure out how many tankless water heaters your home needs, it is strongly recommended that you talk to a plumber or HVAC technician. They will be able to take all of the factors into account and make a recommendation for a properly sized unit or multiple units that will meet the demands for hot water that your household has.