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What Size Water Heater Do I Need?

Updated: Dec 12, 2022

Whether you’re replacing a broken water heater or installing a new one at a new address, you have the opportunity to go green.

Right water heater size for family of 4
Water Heater Options

According to the Environmental Protection Agency, today’s tankless water heaters can be up to 34 percent more efficient than storage tank water heaters.

If realizing that kind of energy savings is important to you, keep reading to find out about the types of tankless water heaters that are on the market and what size tankless water heater that you need for your Bethlehem, PA home.

Types of Tankless Water Heaters

Tankless water heaters are powered by gas or electricity.

Both types of on demand water heaters have their own set of benefits and challenges. Gas tankless water heaters cost more than electric tankless water heaters, but they are often cheaper to operate. Although prices can fluctuate, natural gas is usually less expensive than electricity.

This is worth considering since it’s not uncommon for tankless water heaters to last up to 20 years. The fuel savings over this long-term period can really add up.

Have a large family?

Tankless gas water heaters come in models that address heavy hot water usage needs better than electric tankless water heaters.

Tankless electric water heaters are more energy-efficient to operate than their gas counterparts.

Experts note that about 98 percent of the energy that is used to power these water heaters is used to heat water.

Only about 85 percent of the energy that’s used to power tankless gas water heaters is used to actually heat water. Electric tankless water heaters are also easier to install and maintain than tankless gas water heaters.

Why Size Is Important

Correctly sizing your Bethlehem home’s water heater can mean the difference between a few cold showers on a winter’s morning and complete domestic bliss.

When you’re going for the latter, here are a few factors to consider to get the right size tankless hot water heater.

Space Requirements

When it comes to saving space, tankless water heaters have a considerable edge over storage tank water heaters.

Without a large tank to hide in your utility closet, you’ll have more room to store appropriate tools and accessories. Many electric tankless water heaters take up less space than gas tankless water heaters and are popular with people who have smaller residences.

Besides being smaller than tankless gas water heaters, electric tankless water heaters have fewer components.

They don’t need to be connected to special gas lines, which may require significant gas line rerouting.

If your space isn’t configured to easily handle the installation of a tankless gas water heater, consider installing a tankless water heater electric. This type of tankless water heater offers more flexibility when it comes to water heater placement.

Comfort and Convenience

Having a constant supply of hot water is one of the biggest advantages of going tankless.


An undersized tankless water heater will not produce enough hot water to allow your husband to wash the dishes while your teenager takes a shower.

Most modern households are busy with school sporting events, preparing home-cooked meals, and doing laundry and other household chores.

The last thing that you need is to have your three children wait in line for a shower after soccer, cross-country, and softball practices.

Water Heater Sizing Guide for Homeowners

What Size Water Heater Do I Need?

Since getting the right size water heater is so important, you’ll want help from professionals to determine the right size of water heater that fits your needs and to install it safely.

Here are some factors that professional plumbers consider when they find the size requirement for your tankless water heater.

Home Size

If you have a compact home, chances are high that you can get away with installing a smaller-than-average tankless water heater.

When you turn on your faucet, cold water is passed through an electric element or a gas burner to produce heated water on demand. A house that has only one bathroom, a small kitchen, and laundry will more than likely get as much water as it needs from a standard whole house tankless water heater.

A large home that has multiple luxury bathrooms, a chef’s kitchen, and a commercial-grade washing machine will need a larger tankless water heater or more than one unit.

Reputable plumbers go beyond calculating water heater size by using average house size estimates. They investigate usage requirements based on household size, flow rates, and temperature rise.

Household Size

The number of people in your household and their hot water usage habits are key variables in the quest for a correctly sized tankless water heater.

In a large household of seven or more people, you can expect that multiple people will want to use hot water at the same time to do different activities.

You’ll also want to consider how your hot water needs impact water heater sizing if you enjoy entertaining friends and family at your home regularly.

Understanding the frequency of your family’s peak hot water usage times helps plumbers to find out if a particular tankless water heater model can produce enough hot water to support your household’s needs.

Flow Rate

Whether you’re running your faucet to brush your teeth in the morning or running your dishwasher after dinner, you’ll want to know the flow rates of all of your taps to choose the correct water heater size.

Asking how much water does a shower use and how much hot water does a washing machine need to complete a regular wash load are great starting points to determine the type and size of tankless water heater that you’ll need.

Here are some average flow rates for common hot water needs.

  • Shower 2 gallons per minute

  • Dishwasher 2.5 gallons per minute

  • Laundry 3.5 gallons per minute

If you want to use your shower and the other listed appliances simultaneously, you’ll need a tankless water heater that has a flow rate of at least 8 gallons per minute.

You can also conserve water and help your tankless water heater to operate more efficiently by installing low-flow faucets, shower heads, and other fixtures.

Temperature Rise

Tankless water heater flow rates take water supply temperatures into consideration. If your water supply temperature is 50 degrees Fahrenheit, then you’ll need a water heater that can raise the temperature of your tap water by 50 degrees Fahrenheit to accommodate a comfortable shower of 100 degrees Fahrenheit.

If you have a low-powered tankless water heater, you may have to wait for the water to get hot.

Finding Water Heater Installation Near Me

Whether you decide to install a tankless water heater or a traditional tank water heater, Deluxe Heating and Plumbing can help.

Our plumbers have many years of experience sizing water heater systems to fit a range of household sizes in Bethlehem, PA.

Besides recommending well-known water heater brands that come with generous, peace-of-mind warranties, we back our installation work with a solid warranty that’ll give you the confidence that you need to move forward with your investment.

Give us a call today to find out more details about the pros and cons of installing a tankless water heater vs tank water heater and to get a free quote on installation service.


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