Tankless Water Heater Cost Calculator

Operating Cost Formula:

\[ C = \frac{Q \times 8.34 \times c \times \Delta T}{3412 \times EF} \times P_{kwh} \times t \]

Flow Rate (Q):

GPM

Specific Heat (c):

BTU/lb·°F

Temperature Rise (ΔT):

°F

Efficiency Factor (EF):

Energy Cost (P_kwh):

$/kWh

Usage Time (t):

hours

Operating Cost (C):

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1. What is a Tankless Water Heater Cost Calculator?

Definition: This calculator estimates the operating cost of a tankless water heater based on flow rate, temperature rise, efficiency, and energy costs.

Purpose: It helps homeowners and professionals estimate energy costs for tankless water heating systems.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ C = \frac{Q \times 8.34 \times c \times \Delta T}{3412 \times EF} \times P_{kwh} \times t \]

Where:

$ C $ — Operating cost ($)
$ Q $ — Flow rate (gallons per minute)
$ c $ — Specific heat of water (1.0 BTU/lb·°F)
$ \Delta T $ — Temperature rise (°F)
$ EF $ — Energy efficiency factor (dimensionless)
$ P_{kwh} $ — Electricity cost ($/kWh)
$ t $ — Usage time (hours)

Explanation: The formula calculates the energy required to heat water and converts it to cost based on electricity rates.

3. Importance of Cost Calculation

Details: Accurate cost estimation helps in budgeting, comparing systems, and understanding energy consumption patterns.

4. Using the Calculator

Tips: Enter the flow rate, temperature rise, efficiency factor (default 0.95), electricity cost (default $0.12/kWh), and usage time. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical flow rate for residential use?
A: Most homes use 2-5 GPM, depending on the number of fixtures in simultaneous use.

Q2: Why is 8.34 in the formula?
A: This is the weight of one gallon of water in pounds (8.34 lbs/gal).

Q3: What temperature rise should I use?
A: Typical rise is 50-70°F (from 50°F groundwater to 120-140°F output).

Q4: How does efficiency affect cost?
A: Higher efficiency (closer to 1.0) means lower operating costs.

Q5: Can I use this for gas tankless heaters?
A: No, this calculates electric heater costs only. Gas models require different calculations.