1. What is the Tankless Water Heater Sizing Formula?

The tankless water heater sizing formula calculates the required heating capacity in BTU per hour based on flow rate and desired temperature rise. Proper sizing ensures adequate hot water supply for your household needs.

2. How Does the Calculator Work?

The calculator uses the sizing formula:

Where:

• \( Size \) — Required heating capacity (BTU per hour)
• \( Q \) — Flow rate (gallons per minute)
• \( \Delta T \) — Temperature rise (°F)
• 500 — Constant (BTU required to heat 1 gallon of water by 1°F)
• 60 — Conversion factor (minutes to hours)

Explanation: The formula calculates the energy required to heat a specific flow rate of water by the desired temperature difference.

3. Importance of Proper Sizing

Details: Correct sizing is crucial for efficient operation. Undersized units cannot meet hot water demand, while oversized units waste energy and increase costs.

4. Using the Calculator

Tips: Enter flow rate in gallons per minute and desired temperature rise in °F. Typical flow rates: shower 2.5 GPM, kitchen faucet 1.5 GPM, washer 2.0 GPM.

5. Frequently Asked Questions (FAQ)

Q1: What is temperature rise (ΔT)?
A: Temperature rise is the difference between your desired hot water temperature and the incoming cold water temperature.

Q2: How do I determine my flow rate?
A: Add flow rates of all fixtures that might run simultaneously. Check fixture specifications or measure with a bucket and timer.

Q3: What is a typical temperature rise?
A: For most climates, 60-70°F rise is common. In colder regions, incoming water may be colder, requiring greater temperature rise.

Q4: Can I use this for whole-house sizing?
A: Yes, calculate based on maximum simultaneous hot water usage in your home.

Q5: What about high-efficiency models?
A: The formula provides baseline sizing. Consult manufacturer specifications for specific models and efficiency ratings.