1. What is a Water Heater Wattage Calculator?

Definition: This calculator estimates the electrical wattage required for a water heater based on water volume, temperature rise, recovery time, and efficiency.

Purpose: It helps homeowners, plumbers, and engineers determine the appropriate water heater size for specific needs.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( W \) — Required wattage (watts)
• \( gallons \) — Water volume (gallons)
• \( \Delta T \) — Temperature rise (°F)
• \( hours \) — Recovery time (hours)
• \( EF \) — Efficiency factor (dimensionless)

Explanation: The formula calculates the energy needed to heat water and converts it to electrical wattage requirements.

3. Importance of Proper Wattage Calculation

Details: Correct wattage ensures efficient water heating, prevents energy waste, and avoids undersized systems that can't meet demand.

4. Using the Calculator

Tips: Enter water volume in gallons, desired temperature rise, recovery time (default 1 hour), and efficiency factor (default 0.95). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's the 8.34 factor in the formula?
A: This is the weight of one gallon of water in pounds (lbs/gal).

Q2: What's a typical efficiency factor?
A: Most electric water heaters have an EF of 0.90-0.95, while heat pump models may be 2.0-3.0.

Q3: How do I determine temperature rise?
A: Subtract incoming water temperature from desired output temperature (e.g., 120°F output - 50°F input = 70°F rise).

Q4: What if I need the calculation in BTUs?
A: Remove the 3.412 factor from the formula (this converts BTUs to watt-hours).

Q5: Does this account for heat loss?
A: The efficiency factor accounts for some heat loss, but additional insulation may be needed for long pipe runs.