1. What is a Tankless Water Heater BTU Calculator?

Definition: This calculator determines the BTU (British Thermal Units) capacity needed for a tankless water heater based on flow rate and desired temperature rise.

Purpose: It 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:

• \( BTU \) — British Thermal Units per hour (BTU/h)
• \( Flow \) — Water flow rate (gallons per minute)
• \( \Delta T \) — Temperature rise needed (°F)
• \( 500 \) — Constant (1 gallon of water requires ~500 BTU to raise 1°F)

Explanation: The formula calculates the energy required to heat water at a specific flow rate to your desired temperature.

3. Importance of Proper BTU Calculation

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

4. Using the Calculator

Tips:

• Measure your peak flow rate (simultaneous fixtures)
• Determine your desired temperature rise (incoming water temp to desired output)
• For whole-house systems, consider multiple bathrooms/appliances

5. Frequently Asked Questions (FAQ)

Q1: What's a typical flow rate for homes?
A: 2-5 GPM for most homes (shower=2.5, faucet=1.5, washer=2.0 GPM).

Q2: What temperature rise should I use?
A: Subtract incoming water temp (usually 50-60°F) from desired output (typically 120°F).

Q3: Why 500 in the formula?
A: It's a constant representing BTU needed to heat 1 gallon of water by 1°F (actually 8.33 BTU/lb × 8.34 lb/gal ≈ 500).

Q4: What if my calculated BTU is between standard sizes?
A: Round up to the next available unit size for safety margin.

Q5: Does this account for simultaneous use?
A: Yes, if you enter your total peak flow rate from all fixtures.