1. What is Gas Tankless Water Heater Power Calculator?

Definition: This calculator determines the power required for a gas tankless water heater based on flow rate, temperature rise, and system efficiency.

Purpose: It helps HVAC professionals and homeowners properly size tankless water heaters for their needs.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( P \) — Power requirement (kW)
• \( Q \) — Flow rate (gallons per minute)
• \( c \) — Specific heat of water (BTU/lb·°F)
• \( \Delta T \) — Temperature rise (°F)
• \( EF \) — Efficiency factor (dimensionless, 0-1)

Explanation: The formula calculates the energy needed to heat water at a given flow rate through a specified temperature rise, adjusted for system efficiency.

3. Importance of Proper Power Calculation

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

4. Using the Calculator

Tips: Enter the flow rate in GPM, specific heat (default 1.0 for water), desired temperature rise, and efficiency factor (default 0.82 for typical units). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical efficiency factor for tankless heaters?
A: Most gas tankless units have EF between 0.80-0.95. Electric units may be closer to 0.98.

Q2: How do I determine the temperature rise needed?
A: Subtract your incoming water temperature (usually 50-60°F) from your desired output temperature (typically 120°F).

Q3: What flow rate should I use?
A: Calculate based on simultaneous fixtures. Standard shower = 2.5 GPM, kitchen faucet = 1.5 GPM.

Q4: Why is 8.34 in the formula?
A: This is the weight in pounds of one gallon of water at standard conditions.

Q5: What's the significance of 3412?
A: This converts BTU/hr to kW (1 kW = 3412 BTU/hr).