1. What is a 15 GPM Tankless Water Heater Calculator?

Definition: This calculator determines if a 15 GPM tankless water heater meets your hot water demand by summing the flow rates of all fixtures.

Purpose: Helps size commercial or multi-unit tankless water heater systems to ensure adequate hot water supply.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Q \) — Total hot water demand (gallons per minute)
• \( Q_i \) — Flow rate of each fixture type

Explanation: Sums the simultaneous hot water demand from all fixtures to determine if a 15 GPM unit can handle the load.

3. Importance of Proper Sizing

Details: Undersized units cause inadequate hot water, while oversized units waste energy. Commercial applications require precise calculations.

4. Using the Calculator

Tips: Enter the number of each fixture type. The calculator uses standard flow rates:

• Shower: 2.5 GPM
• Sink: 1.5 GPM
• Dishwasher: 1.5 GPM
• Washing Machine: 2.0 GPM

5. Frequently Asked Questions (FAQ)

Q1: What applications need 15 GPM tankless heaters?
A: Small commercial buildings, multi-unit residences (3-4 units), or large homes with high simultaneous demand.

Q2: What if my total exceeds 15 GPM?
A: Consider multiple units in parallel or a larger commercial system (20+ GPM).

Q3: How accurate are the default flow rates?
A: These are industry standards. For precise calculations, use actual fixture specs.

Q4: Does this account for temperature rise?
A: No, this calculates flow only. Temperature requirements affect the heater's BTU capacity.

Q5: Should I add a safety factor?
A: Commercial applications often add 10-20% to the calculated demand.