Formula
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
- Water density 1 kg/L and specific heat 4.186 kJ/(kg·K). Pipe losses and standby losses are excluded.
Example Calculation
- Flow rate: 8 L/min
- Duration: 10 min
- Temperature rise: 25 K
- Heater efficiency: 90 %
- Energy price: 0.2 currency/kWh
- Water and sewer price: 3 currency/m³
80 L warmed by 25 K at 90% efficiency needs about 2.584 kWh; the entered tariffs total about 0.757.
Frequently asked questions
How do I use this calculator?
Enter flow rate, duration, temperature rise, heater efficiency, energy price, water and sewer price. The result updates automatically. Use Reset to restore the example values.
What method does it use?
liters=flow × duration; heat input kWh=liters × 4.186 × ΔT /3600 / efficiency.. Water density 1 kg/L and specific heat 4.186 kJ/(kg·K). Pipe losses and standby losses are excluded.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.