1. What is the Tankless Water Heater Size Calculation?

The tankless water heater size calculation determines the required heating capacity in BTU per hour based on the total flow rate of fixtures and the desired temperature rise. Proper sizing ensures adequate hot water supply for your household needs.

2. How Does the Calculator Work?

The calculator uses the tankless water heater size formula:

Where:

• \( Fixture\ GPM \) — Total flow rate of all fixtures (gallons per minute)
• \( \Delta T \) — Temperature rise required (°F)
• \( 500 \) — Constant factor (BTU per gallon per °F)
• \( 60 \) — Conversion factor (minutes to hours)

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

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: Calculate total GPM by adding flow rates of all fixtures that may run simultaneously. Determine ΔT by subtracting incoming water temperature from desired output temperature.

5. Frequently Asked Questions (FAQ)

Q1: How do I determine fixture GPM?
A: Check manufacturer specifications for each fixture or use flow rate calculators. Typical values: shower 2.5 GPM, faucet 1.5 GPM, dishwasher 1.5 GPM.

Q2: What is a typical ΔT value?
A: Depends on climate. Common ΔT values range from 45°F to 75°F. Measure incoming water temperature for accuracy.

Q3: Should I consider simultaneous usage?
A: Yes, calculate GPM for the maximum number of fixtures likely to be used at the same time (e.g., shower + dishwasher).

Q4: What about high-efficiency models?
A: This calculation provides base requirements. Consider efficiency ratings and manufacturer recommendations for specific models.

Q5: Is this calculation suitable for whole-house systems?
A: Yes, this formula is designed for whole-house tankless water heater sizing calculations.