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Tankless Water Heater Flow Rate Calculator
Calculate the heater power needed for a given flow and temperature rise.
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Calculate the heater power needed for a given flow and temperature rise.
Tankless Water Heater Flow Rate Estimator
Enter your numbers below for an instant estimate.
0
💡 Tip: P = flow x 4.186 x rise / 60.
How It Works
Key concepts behind this calculator
1
Enter Values
Fill in each field with your own numbers.
2
Calculate
Results update as you change the inputs.
3
Review
Read the breakdown and the explanation.
4
Adjust
Change values to compare scenarios.
Quick Reference Guide
Tankless Quick Guide
Typical values for reference.
| L/min | Inlet °C | Outlet °C | kW |
|---|---|---|---|
| 4 | 10 | 40 | 8.4 kW |
| 8 | 10 | 40 | 16.7 kW |
| 12 | 10 | 40 | 25.1 kW |
| 16 | 5 | 40 | 39.1 kW |
| Rule of Thumb | Check inputs | Use as a guide | Round sensibly |
Common Questions
Tankless Water Heater Calculator FAQ
Answers to common questions about this calculator.
Heat.
It gives a quick estimate of tankless water heater flow rate from the values you enter.
No. It is a planning estimate, so check important figures with a professional or official source.
Yes. Edit any field and the result updates when you calculate.