1. What is Tankless Water Heater Sizing?

Tankless water heater sizing determines the required heating capacity (in BTU/hr) to meet your household's hot water demand. Proper sizing ensures you have sufficient hot water flow while maintaining energy efficiency.

2. How Does the Calculator Work?

The calculator uses the BTU calculation formula:

Where:

• \( Q_{peak} \) — Peak flow rate in gallons per minute (GPM)
• \( \Delta T \) — Temperature rise required in degrees Fahrenheit (°F)
• 500 — Constant (weight of 1 gallon of water × specific heat capacity)
• 60 — Conversion factor from minutes to hours

Explanation: The formula calculates the energy required to heat water from incoming temperature to desired temperature at your peak flow rate.

3. Importance of Proper Sizing

Details: Correct sizing prevents issues like insufficient hot water, energy waste, and premature equipment failure. Oversized units waste energy while undersized units cannot meet demand.

4. Using the Calculator

Tips: Determine your peak flow rate by adding flow rates of all fixtures that might run simultaneously. Typical temperature rise is 60-70°F for most climates.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical peak flow rate for a household?
A: Average households range from 3-7 GPM. Larger homes with multiple bathrooms may require 7-10 GPM.

Q2: How do I determine the temperature rise needed?
A: Subtract your incoming water temperature from your desired output temperature. Incoming water is typically 40-50°F, desired output is 110-120°F.

Q3: What if I have high-flow fixtures?
A: Rain showerheads (2.5+ GPM) and multiple fixtures running simultaneously significantly increase peak flow requirements.

Q4: Should I add a safety factor?
A: It's recommended to add 10-20% safety margin to account for future needs and temperature fluctuations.

Q5: Can this calculator be used for commercial applications?
A: Yes, but commercial applications often require more complex calculations considering simultaneous use factors and recovery rates.