1. What is an Electric Tankless Water Heater Calculator?

Definition: This calculator determines the power required (in kW) for an electric tankless water heater based on flow rate and desired temperature rise.

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

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( kW \) — Power requirement (kilowatts)
• \( GPM \) — Flow rate (gallons per minute)
• \( \Delta T \) — Temperature rise (°F)
• \( 0.139 \) — Conversion factor (for water)

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: Correct sizing ensures adequate hot water supply while avoiding excessive energy consumption or equipment costs.

4. Using the Calculator

Tips: Enter the desired flow rate in GPM and the required temperature rise (difference between incoming water temp and desired output temp). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical flow rate for residential use?
A: Most homes need 2-5 GPM, depending on the number of simultaneous fixtures.

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: Why is the conversion factor 0.139?
A: This accounts for the specific heat of water and unit conversions (1 BTU/lb-°F × 8.33 lb/gal × 1 kW/3412 BTU/hr × 60 min/hr).

Q4: What if I need multiple units?
A: For multiple heaters, divide the total kW by the number of units you plan to install.

Q5: Does this account for voltage requirements?
A: No, you'll need to ensure your electrical service can provide the calculated kW at 240V (common for tankless heaters).