1. What is a Tankless Water Heater Sizing Calculator?

Definition: This calculator determines the required size of a tankless water heater based on the total flow rate (GPM) of all hot water fixtures in your home.

Purpose: It helps homeowners and plumbers select an appropriately sized tankless water heater to meet household hot water demands.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Q \) — Total flow rate (gallons per minute)
• \( Q_i \) — Flow rate of individual fixtures (GPM)

Explanation: The flow rates of all potential simultaneously used fixtures are summed to determine the peak demand.

3. Importance of Proper Sizing

Details: Correct sizing ensures adequate hot water supply, energy efficiency, and prevents overworking the unit.

4. Using the Calculator

Tips: Enter the flow rates for all hot water fixtures in your home. Default values are provided based on typical fixture flow rates.

5. Frequently Asked Questions (FAQ)

Q1: What if I don't know my fixture flow rates?
A: Use the provided defaults which represent typical values for standard fixtures.

Q2: Should I include fixtures that won't be used simultaneously?
A: No, only include fixtures that might run at the same time for worst-case scenario sizing.

Q3: What about temperature rise considerations?
A: This calculator provides flow rate requirements. Temperature rise (based on groundwater temp) affects heating capacity but not flow rate.

Q4: How do I find my actual fixture flow rates?
A: Check manufacturer specs or measure by timing how long it takes to fill a 1-gallon container.

Q5: Should I add a safety factor?
A: It's recommended to add 10-20% to the calculated GPM for unexpected demand or future additions.