1. What is a Tankless Water Heater Capacity Calculator?

Definition: This calculator estimates the required capacity of a tankless water heater based on flow rate, desired temperature rise, and a constant.

Purpose: It helps homeowners and plumbers determine the appropriate size tankless water heater needed for a given application.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Capacity \) — Heating capacity required (BTU/h or kW)
• \( Q \) — Flow rate (gallons per minute)
• \( \Delta T \) — Temperature rise needed (°F)
• \( constant \) — Conversion factor (500 for BTU/h)

Explanation: The flow rate multiplied by temperature rise gives the basic energy requirement, which is then scaled by the conversion factor.

3. Importance of Proper Sizing

Details: Correct capacity calculation ensures adequate hot water supply, energy efficiency, and prevents overworking the unit.

4. Using the Calculator

Tips: Enter the flow rate in gpm, desired temperature rise in °F, and constant (default 500 for BTU/h). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What flow rate should I use?
A: Calculate the total flow rate of all fixtures that might run simultaneously (e.g., shower + sink).

Q2: How do I determine temperature rise?
A: Subtract your incoming water temperature from desired output temperature (e.g., 120°F output - 50°F input = 70°F rise).

Q3: When would I change the constant?
A: Use 500 for BTU/h calculations. For kW, use 0.044 instead (1 kW = 3412 BTU/h).

Q4: What's a typical temperature rise?
A: Most households need 60-70°F rise for comfortable hot water, but this depends on your climate and groundwater temperature.

Q5: How much capacity is too much?
A: Oversizing by 10-20% is acceptable, but significantly larger units waste energy and cost more to operate.