Tankless Hot Water Heater Size Calculator

BTU Calculation Formula:

\[ BTU = Q \times 8.34 \times 60 \times \Delta T \]

Required BTU:

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is the Tankless Water Heater Size Calculation?

The tankless water heater size calculation determines the required heating capacity in BTU (British Thermal Units) per hour based on the desired flow rate and temperature rise. Proper sizing ensures adequate hot water supply for your needs.

2. How Does the Calculator Work?

The calculator uses the BTU calculation formula:

\[ BTU = Q \times 8.34 \times 60 \times \Delta T \]

Where:

\( Q \) — Flow rate in gallons per minute (GPM)
\( 8.34 \) — Weight of one gallon of water in pounds
\( 60 \) — Minutes per hour conversion
\( \Delta T \) — Temperature rise in degrees Fahrenheit (°F)

Explanation: The formula calculates the energy required to heat water by multiplying flow rate by water weight, time conversion, and temperature difference.

3. Importance of Proper Sizing

Details: Correct sizing prevents undersizing (insufficient hot water) and oversizing (energy waste). Proper BTU calculation ensures the unit can handle peak demand while operating efficiently.

4. Using the Calculator

Tips: Enter the desired flow rate in GPM and the required temperature rise (°F). Typical temperature rise is 40-70°F depending on incoming water temperature and desired output temperature.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical flow rate for residential use?
A: Standard shower: 2.0-2.5 GPM, kitchen faucet: 1.5-2.0 GPM, bathroom faucet: 1.0-1.5 GPM. Calculate total GPM for simultaneous use.

Q2: How do I determine the temperature rise needed?
A: Subtract your incoming groundwater temperature from your desired output temperature. Typical groundwater temperatures range from 40-70°F.

Q3: What if I need multiple fixtures running simultaneously?
A: Add the flow rates of all fixtures that might be used at the same time and use that total GPM in your calculation.

Q4: Are there other factors to consider besides BTU?
A: Yes, consider gas line capacity, venting requirements, and minimum flow rate activation for gas models.

Q5: What's the difference between natural gas and electric models?
A: Gas models typically have higher BTU capacities and are better for whole-house applications. Electric models are limited by electrical service capacity.