1. What is a Tankless Water Heater Sizing Calculator?

Definition: This calculator estimates the required flow rate (GPM) for a tankless water heater based on simultaneous fixture usage.

Purpose: It helps homeowners and plumbers properly size tankless water heaters for medium households with typical 5 GPM demand.

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 fixtures that might be used simultaneously are added together to determine the total required capacity.

3. Importance of Proper Sizing

Details: Correct sizing ensures adequate hot water supply without oversizing the unit, which improves energy efficiency and reduces costs.

4. Using the Calculator

Tips: Enter the flow rates for shower (default 2.5 GPM), sink (default 1.5 GPM), and dishwasher (default 1.0 GPM). These represent typical simultaneous usage in medium households.

5. Frequently Asked Questions (FAQ)

Q1: Why is 5 GPM typical for medium households?
A: This accounts for simultaneous use of 1 shower (2.5 GPM), 1 sink (1.5 GPM), and 1 dishwasher (1.0 GPM).

Q2: How do I find my fixture flow rates?
A: Check manufacturer specs or measure flow rate by timing how long it takes to fill a 1-gallon container.

Q3: Should I consider temperature rise?
A: Yes, this calculator determines flow rate only. You'll also need to consider the required temperature increase based on your climate.

Q4: What if I have more fixtures?
A: Add their flow rates to the calculation if they might be used simultaneously with the others.

Q5: Is there a safety factor?
A: The default values already include some margin, but you may add 10-20% for peak demand periods.