1. What is a Tankless Water Heater Calculator?

Definition: This calculator estimates the power required for a tankless water heater based on flow rate, temperature rise, and system efficiency.

Purpose: It helps homeowners and plumbers determine the appropriate size for tankless water heater installations.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( kW \) — Power required (kilowatts)
• \( Flow \) — Water flow rate (gallons per minute)
• \( Rise \) — Temperature increase desired (°F)
• \( Efficiency \) — System efficiency (0-1, where 1 is 100% efficient)

Explanation: The formula calculates the energy needed to heat a given flow of water by a specified temperature rise, adjusted for system efficiency.

3. Importance of Proper Sizing

Details: Correctly sizing a tankless water heater ensures adequate hot water supply while avoiding oversized, inefficient units.

4. Using the Calculator

Tips: Enter the flow rate in GPM, desired temperature rise in °F, and system efficiency (default 0.98 for electric units). 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: What temperature rise should I use?
A: Typical rises are 50-70°F (from 50°F groundwater to 120-140°F output).

Q3: How does efficiency affect the calculation?
A: Lower efficiency means more power is needed (0.98 for electric, 0.82 for gas units).

Q4: What does the 500 constant represent?
A: It combines the weight of water (8.33 lb/gal) and the BTU to kW conversion factor.

Q5: Should I round up the calculated kW?
A: Yes, always round up to the nearest available unit size for safety margin.