Electric Tankless Water Heater Calculator

Power Formula:

\[ P = \frac{Q \times \rho \times c_p \times \Delta T}{\text{efficiency}} \]

Flow Rate (Q):

L/min

Water Density (ρ):

kg/L

Specific Heat (c_p):

kJ/kg·°C

Temperature Rise (ΔT):

°C

Efficiency:

(0-1)

Required Power (kW):

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1. What is an Electric Tankless Water Heater Calculator?

Definition: This calculator determines the power required for an electric tankless water heater based on water flow rate, temperature rise, and system efficiency.

Purpose: It helps homeowners and plumbers properly size electric tankless water heaters for residential or commercial applications.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ P = \frac{Q \times \rho \times c_p \times \Delta T}{\text{efficiency}} \]

Where:

\( P \) — Required power (kW)
\( Q \) — Water flow rate (L/min)
\( \rho \) — Water density (kg/L)
\( c_p \) — Specific heat of water (kJ/kg·°C)
\( \Delta T \) — Temperature rise (°C)
efficiency — System efficiency (0-1)

Explanation: The formula calculates the energy needed to heat a given flow of water by a specified temperature rise, accounting for system efficiency.

3. Importance of Proper Sizing

Details: Correct power calculation ensures adequate hot water supply, energy efficiency, and prevents overloading electrical systems.

4. Using the Calculator

Tips: Enter your desired flow rate, temperature rise (difference between incoming and desired water temperature), and system efficiency. Default values are provided for typical conditions.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical flow rate for residential use?
A: Standard shower heads use 6-9 L/min, while whole-house systems may need 12-20 L/min.

Q2: What temperature rise should I calculate for?
A: For most climates, calculate for a 35-45°C rise (from ~10°C groundwater to 45-55°C hot water).

Q3: Why is efficiency important?
A: Modern electric tankless heaters are ~98% efficient. Lower efficiency means more power needed.

Q4: How do I convert kW to amperage?
A: For 240V systems: Amps = (kW × 1000) ÷ 240. A 24 kW unit draws about 100A at 240V.

Q5: Can I use this for multiple fixtures?
A: Yes, sum the flow rates of all fixtures that might run simultaneously for whole-house sizing.