1. What is a Tankless Hot Water Heater Calculator?

Definition: This calculator estimates the power required for a tankless water heater based on flow rate and desired temperature rise.

Purpose: It helps homeowners and plumbers determine the appropriate size of tankless water heater needed for a specific application.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( kW \) — Required power (kilowatts)
• \( GPM \) — Flow rate (gallons per minute)
• \( \Delta T \) — Temperature rise (°F)
• \( 0.139 \) — Conversion factor

Explanation: The formula calculates the energy needed to heat a given flow rate of water by a specified temperature difference.

3. Importance of Proper Sizing

Details: Correctly sizing a tankless water heater ensures adequate hot water supply while avoiding excessive energy consumption or equipment costs.

4. Using the Calculator

Tips:

• Measure your actual flow rate (GPM) from fixtures
• Determine your needed temperature rise (incoming water temp vs desired output temp)
• For whole-house systems, calculate based on simultaneous fixture use

5. Frequently Asked Questions (FAQ)

Q1: What's a typical flow rate for showers?
A: Standard showerheads are 2.0-2.5 GPM, while low-flow models are 1.5-1.8 GPM.

Q2: How do I determine temperature rise?
A: Subtract your incoming groundwater temperature from your desired output temperature (typically 120°F).

Q3: What if I need multiple fixtures simultaneously?
A: Add the GPM of all fixtures that might run together and use that total in your calculation.

Q4: What's the conversion factor 0.139?
A: This combines the specific heat of water (1 BTU/lb-°F), water density (8.33 lb/gal), and unit conversions.

Q5: Should I add a safety factor?
A: It's common to add 10-20% to the calculated kW to account for variations in incoming water temperature.