How Big of a Tankless Water Heater Do I Need?

Choosing a tankless water heater that fits your home can prove challenging. You must consider the components in your home and how many LPMs your plumbing system needs. Whether you want to replace your current water heater or expand your house, you need accurate measurements for the perfect product.



You’re asking yourself, “How big of a tankless water heater do I need?” local plumbing experts provide a few answers to this question. Continue reading to discover how to choose the right size tankless water heater.

What Is a Tankless Water Heater?

The average water heater has a tank that stores up to 190 litres of water. It keeps the water at a stable, hot temperature by heating its contents when it senses a temperature drop. You may notice that when multiple areas use hot water at one time, the hot water eventually runs out.

While a tankless water heater doesn’t store hot water, it uses more pipe and an exchanger to keep the water warm. The cold water moves back and forth through the pipes. When the water flows through the exchanger, the exchanger makes the temperature rise. 

Like water heaters that use tanks, the water from tankless heaters takes a few moments to heat up after turning the faucet. However, tankless water heaters will consistently provide hot water throughout the day. You can use multiple appliances at one time like showers, the dishwasher, and the washing machine.

You’ll find a variety of tankless heaters and additional components on the market. Some types provide more energy efficiency than others. Most models are designed to reduce the amount of wasted water within a building. 

What Does Litres Per Minute Mean?

Litres per minute (LPM), also called the flow rate, refers to the litres of water your showerhead releases within one minute. However, LPMs aren’t limited to showerheads. Since tankless water heaters heat water on demand, you need to know how many LPMs your home uses with each appliance. 

Below, you’ll find general LPM estimations from common appliances that use water. These appliances are ordered from greatest LPM to least. 

• Washing machines = 15 LPM
• Showerheads = 7.5 LPM
• Bathtubs = 7.5 LPM
• Dishwashers = 5.5 LPM
• Kitchen sinks = 5.5 LPM
• Washroom sinks = 4 LPM

Remember that each measurement works for each individual appliance. So if your home has four showerheads, you need a water heater that accommodates 30 LPMs. If you only plan to run a few appliances at a time, you can purchase a model with a lower LPM. 

However, choosing models that accommodate multiple appliances is the best decision. If you live with family members or have roommates, you can count on multiple people using water simultaneously. Even if you live alone, running the dishwasher while you take a shower provides added and often necessary convenience. 

How Do You Calculate Size?

When your main question is “How big of a tankless water heater do I need?”, you need accurate calculations that factor in your local climate. In Winnipeg, MB, temperatures drop below freezing. Groundwater stays cool all year. So your water heater will need to accommodate more LPMs than a house located farther south. 

Since you can choose from a plethora of models and components, you’ll want to shop around for the best fit for your home. If you want to run multiple appliances at once, the heater’s LPM should accommodate that. Running a dishwasher, a washing machine, and a showerhead at the same time requires a minimum of 28 LPMs. 

If you live with multiple people in a large house, consider purchasing multiple water heaters. You can install one heater for the ground floor and a second one for the upper floor. Simply calculate the LPMs for each separate floor to find matching products. 

Choosing a Tankless Water Heater

Most manufacturers will provide a guide on their website to help you choose a water heater. These guides usually include your area’s lowest temperature combined with the number of appliances that use water in your house. For Winnipeg, MB, find the average groundwater temperature to help you gauge your needs. 

You can choose from two types of water heaters. Electric tankless water heaters run on electricity. They usually come at a less expensive price. 

Gas tankless water heaters usually come with a higher price tag. You’ll pay more both for the product and installation. Plus, the cost of fuel fluctuates. A gas water heater will only be more cost-effective than an electric one when fuel prices dip lower than electricity.   

Advantages and Disadvantages of Tankless Water Heaters

Why should you choose a tankless water heater? Are there any disadvantages? When you know a product from all angles, you can make a more informed decision for your house. 

Tankless water heaters have several advantages. For example, they don’t take up as much space in your home as a hot water tank. Water tanks use up space that you could transform into a storage closet.

Your tankless water heater provides an endless supply of hot water to your house. Water heater tanks will eventually empty out. You’ll have to wait for the freshwater supply to reheat.

Since tankless water heaters don’t constantly heat the water, you save energy. Hot water tanks expend energy regularly in order to keep water warm. 

The cons of a tankless water heater include maintenance and downtime. If the power goes out, your electric tankless water heater will go out with it. Additionally, tankless heaters require more maintenance and upkeep due to water scale building up. 

Get Help Selecting Water Heaters for Your Needs with King Services

Did you find satisfactory answers to “How big of a tankless water heater do I need?” If so, you’ll have an easier time choosing a model for your house. If not, you can seek advice from King Services. Call us at (204) 633-9010. 

Don’t forget to read our water heater maintenance checklist to keep your water heater in prime condition throughout the year.