1. What is a Tankless Water Heater Capacity Calculator?

Definition: This calculator determines the required heating capacity (in BTU/h) for a tankless water heater based on desired flow rate and temperature rise.

Purpose: Helps homeowners and plumbers properly size tankless water heaters for residential or commercial applications.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• Capacity — Required heating capacity (BTU/h)
• GPM — Flow rate in gallons per minute
• ΔT — Temperature rise needed (°F)
• 500 — Conversion factor (1 gallon of water raised by 1°F per minute ≈ 500 BTU/h)

Explanation: The formula calculates the energy needed to heat water at a specific flow rate through a desired temperature increase.

3. Importance of Proper Sizing

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

4. Using the Calculator

Tips:

• Determine your peak hot water demand (GPM)
• Calculate ΔT by subtracting incoming water temperature from desired output temperature
• For whole-house systems, consider simultaneous appliance use

5. Frequently Asked Questions (FAQ)

Q1: What's a typical GPM for household fixtures?
A: Shower: 1.5-2.5 GPM, Kitchen faucet: 1.0-1.5 GPM, Washing machine: 1.5-3.0 GPM.

Q2: How do I determine incoming water temperature?
A: Groundwater temperatures vary by region (typically 40-60°F). Measure or check local data.

Q3: What if I need to serve multiple fixtures simultaneously?
A: Add the GPM of all fixtures that might run together when calculating total flow rate.

Q4: Why is the conversion factor 500?
A: It accounts for the specific heat of water (8.33 lb/gal × 60 min/h × 1 BTU/lb-°F ≈ 500).

Q5: Should I add a safety factor?
A: Many professionals add 10-20% capacity buffer for temperature fluctuations and future needs.