A Comprehensive Guide: Commercial Tankless Water Heaters

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Drain Down King
October 27, 2023
Commercial tankless water heater

Navigating Commercial Tankless Water Heater Sizing: A Comprehensive Guide

In the bustling world of commercial establishments, ensuring a consistent and efficient supply of hot water is non-negotiable. Enter the revolutionary tankless water heater. But with its myriad of options, how does one determine the right size for a commercial setting? This guide delves deep into the art and science of commercial tankless water heater sizing, ensuring you make an informed decision.

Why Sizing Matters

At the intersection of efficiency and utility, the importance of correctly sizing a tankless water heater cannot be overstated:

  1. Operational Efficiency: A properly sized unit runs optimally, leading to energy savings and longevity of the device.
  2. Consistent Supply: Ensure that the hot water demand of your establishment is met without hitches or delays.
  3. Cost Implications: Avoid overspending on an oversized unit or frequently replacing an undersized one.

Factors to Consider for Commercial Tankless Water Heater Sizing

  1. Peak Demand: Analyze your establishment's peak hot water demand. This involves considering simultaneous usage scenarios, like multiple showers running concurrently in a hotel.
  2. Inlet Water Temperature: The colder the incoming water, the harder the heater has to work. This varies by region and season.
  3. Desired Output Temperature: Determine the temperature at which you need the water to be delivered. This can vary based on the intended use, from dishwashing to bathing.
  4. Flow Rate: Measured in gallons per minute (GPM), it's the volume of water the unit needs to heat during peak usage.

A Step-by-Step Sizing Guide

  1. List All Hot Water Devices: Catalog every appliance and fixture that will demand hot water.
  2. Calculate Total GPM: Sum up the flow rates of all these devices to get a cumulative GPM. This will give you an idea of the maximum flow rate required.
  3. Assess Temperature Rise: Subtract the inlet water temperature from your desired output temperature. The result is the temperature rise your heater must achieve.
  4. Consult Manufacturer Specifications: Armed with your flow rate and temperature rise, consult with manufacturers or their spec sheets to find the optimal unit.


The world of commercial tankless water heaters offers unparalleled efficiency and convenience. However, its benefits are best realized when the unit is sized perfectly to meet the demands of your establishment. By considering peak demand, regional temperatures, desired output, and flow rates, you can ensure a seamless hot water experience, optimizing both operational efficiency and cost savings.

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Drain Down King
Founder, Pipe Drainer