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

Definition: This calculator determines the required flow rate (in gallons per minute) for an electric tankless water heater by summing the flow rates of all simultaneous fixtures.

Purpose: It helps homeowners and plumbers properly size electric tankless water heaters to meet hot water demand.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

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

Explanation: The calculator sums the flow rates of all fixtures that might run simultaneously to determine the minimum required flow capacity for the tankless heater.

3. Importance of Proper GPM Calculation

Details: Correct GPM calculation ensures your tankless water heater can meet simultaneous hot water demands without temperature fluctuations or insufficient flow.

4. Using the Calculator

Tips: Enter the flow rate (GPM) for each fixture that might run simultaneously. Common values are 1.5 GPM for bathroom faucets, 2.0-2.5 GPM for showers, and 0.5 GPM for dishwasher.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical flow rate for common fixtures?
A: Bathroom faucet: 0.5-1.5 GPM, Shower: 1.5-2.5 GPM, Kitchen faucet: 1.0-2.2 GPM, Dishwasher: 0.5-1.5 GPM, Washing machine: 1.0-2.0 GPM.

Q2: How many fixtures can run simultaneously?
A: This depends on your heater's capacity. Most residential units handle 2-3 fixtures at once. Commercial units can handle more.

Q3: What if my calculated GPM exceeds my heater's capacity?
A: Consider a higher capacity unit, prioritize fixture use, or install multiple point-of-use heaters.

Q4: Does temperature rise affect GPM requirements?
A: Yes, but this calculator focuses on flow rate. Temperature calculations require additional information about incoming water temperature.

Q5: Should I add a safety margin?
A: It's recommended to add 10-20% to your calculated GPM to account for variations in actual usage and future needs.