1. What is an Electric Tankless Water Heater Sizing Calculator?

Definition: This calculator determines the required size (in GPM) of an electric tankless water heater for commercial or multi-unit applications.

Purpose: It helps plumbers, contractors, and building owners properly size tankless water heaters to meet simultaneous hot water demand.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Q \) — Total flow rate required (gallons per minute)
• \( Q_i \) — Flow rate of each individual fixture

Explanation: The calculator sums the flow rates of all potential simultaneously operating fixtures to determine the total demand.

3. Importance of Proper Sizing

Details: Correct sizing ensures adequate hot water supply, prevents system overload, and maximizes energy efficiency.

4. Using the Calculator

Tips: Enter the flow rate (GPM) for each type of fixture in your building. Default values are provided based on standard fixture flow rates.

5. Frequently Asked Questions (FAQ)

Q1: What's the typical flow rate for a shower?
A: Standard showers use 2.5 GPM, while low-flow models may use 1.5-2.0 GPM.

Q2: Why round up to the nearest 5 GPM?
A: Tankless heaters come in standard sizes (5, 10, 15, 20 GPM etc.), and it's better to oversize slightly than undersize.

Q3: How many fixtures can run simultaneously?
A: This depends on your usage patterns. For commercial spaces, assume most fixtures could run simultaneously during peak times.

Q4: What about temperature rise considerations?
A: This calculator determines flow capacity only. You'll also need to consider the required temperature increase based on incoming water temperature.

Q5: How do I reduce the required heater size?
A: Install low-flow fixtures, stagger usage patterns, or consider multiple smaller units in parallel.