Setting water temp on tankless water heater - How to Size Your Tankless Water Heater: A Quick Guide

Securing consistent hot water for your home goes beyond just picking any tankless water heater; it’s about choosing one that’s perfectly sized. Too small, and you’re in for cold water surprises; too large, and you’re overspending on upfront costs. Discover how to pinpoint the ideal size for your home with our streamlined guide. 

Step 1: Identify Simultaneous Usage 

Start by understanding which fixtures in your home, such as showers, dishwashers, or faucets, you might use at the same time. 

Step 2: Calculate the Total Flow Rate 

This is about gauging the water volume you’d need, measured in gallons per minute (GPM). Sum up the flow rates of all the fixtures you’d use concurrently. For instance, combining a standard shower (2.0 GPM), a dishwasher (2.5 GPM), and a faucet (1 GPM) results in a requirement of 5.5 GPM. 

Fixture Type  Flow Rate (GPM) 
Standard Shower  2.0 
Dishwasher  2.5 
Faucet  1.0 
High-Efficiency Washer  1.0-1.5 
Bathtub  4.0-7.0 

Step 3: Determine Groundwater Temperature 

Depending on where you reside, groundwater temperatures can differ. While southern parts of Ontario might average around 10°C, some northern parts can be close to freezing. 

Step 4: Assess the Required Temperature Rise 

Determine the difference between your desired faucet temperature (usually ranging from 45°C to 60°C) and the groundwater temperature. For example, with a groundwater temperature of 8° C, you’d need a temperature rise of 42° C to achieve a desired 50° C. 

Step 5: Match Your Needs to the Right Tankless Water Heater 

With your calculated flow rate and temperature rise, you can now select the aptly sized tankless water heater. If your home demands 6.5 GPM with a temperature rise of 35°C, opt for a tankless heater rated for 6-8 GPM at a 33°C temperature rise. 

Woodbridge GTA ClimateCare Has You Covered 

At Woodbridge GTA ClimateCare, we prioritize your home’s comfort and efficiency. Sizing a tankless water heater might seem tricky, but our team is here to help. Contact us today for informed choices and expert installations! 

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