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Tankless Water Heater Sizing Formula:
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The Tankless Water Heater Sizing Calculator helps determine the appropriate size tankless water heater needed for your household by calculating the total gallons per minute (GPM) requirement based on your fixtures' flow rates.
The calculator uses the simple formula:
Where:
Explanation: The equation sums up the flow rates of all fixtures that might be used simultaneously to determine the total GPM requirement for your tankless water heater.
Details: Properly sizing a tankless water heater is crucial for ensuring adequate hot water supply, energy efficiency, and preventing system overload. Undersized units may not meet demand, while oversized units waste energy.
Tips: Enter the total flow rate of fixtures in gallons per minute. Consider all fixtures that might be used simultaneously (showers, sinks, appliances) for accurate sizing.
Q1: What is the average GPM for common fixtures?
A: Standard shower: 2.0-2.5 GPM, kitchen sink: 1.5-2.2 GPM, bathroom sink: 0.5-1.5 GPM, washing machine: 1.5-3.0 GPM.
Q2: Should I consider temperature rise when sizing?
A: Yes, temperature rise (difference between incoming water temp and desired output temp) affects the required unit size. Colder climates may require larger units.
Q3: How many fixtures can run simultaneously?
A: This depends on your total GPM requirement. A typical household might run 2-3 fixtures simultaneously during peak usage.
Q4: What about gas vs electric tankless units?
A: Gas units typically have higher flow rates but require proper venting. Electric units may have lower flow rates but easier installation.
Q5: Should I add a safety margin to the calculated GPM?
A: It's recommended to add 10-20% safety margin to account for future needs and ensure adequate performance during peak demand.