Tankless Hot Water Heater GPM Calculator

Tankless Water Heater GPM Formula:

\[ Q = \frac{kW \times 3412}{\Delta T \times 500 / 60} \]

Flow Rate (GPM):

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1. What is the Tankless Water Heater GPM Calculator?

The Tankless Hot Water Heater GPM Calculator determines the flow rate in gallons per minute that a tankless water heater can deliver based on its power input and the desired temperature rise. This helps in selecting the right unit for your household needs.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ Q = \frac{kW \times 3412}{\Delta T \times 500 / 60} \]

Where:

\( Q \) — Flow rate in gallons per minute (GPM)
\( kW \) — Power input in kilowatts
\( \Delta T \) — Temperature rise in degrees Fahrenheit
3412 — Conversion factor (BTU per kWh)
500 — BTU required to heat 1 gallon of water by 1°F
60 — Minutes per hour

Explanation: The formula calculates how many gallons of water can be heated per minute based on the heater's power capacity and the temperature difference needed.

3. Importance of GPM Calculation

Details: Proper GPM calculation ensures your tankless water heater can meet your household's simultaneous hot water demands, preventing insufficient hot water during peak usage times.

4. Using the Calculator

Tips: Enter the power rating of your tankless water heater in kW and the desired temperature rise (difference between incoming cold water and desired hot water temperature). Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical GPM requirement for a household?
A: Most households require 2-5 GPM depending on the number of bathrooms and simultaneous fixtures used.

Q2: How do I determine the temperature rise needed?
A: Subtract your incoming groundwater temperature from your desired hot water temperature (typically 120°F).

Q3: What factors affect tankless water heater performance?
A: Incoming water temperature, flow rate demand, unit efficiency, and mineral buildup can all impact performance.

Q4: Can I use this calculator for gas tankless water heaters?
A: This calculator is designed for electric units. Gas units use different BTU calculations and would require a modified formula.

Q5: What if my calculated GPM seems too low?
A: You may need a higher kW unit, or consider installing multiple units for different parts of your home to meet demand.