Measure hot water demand from showers, sinks, baths, and laundry. Get mixed water, energy estimates, and planning figures for smarter daily use.
| Case | Showers/Day | Shower Minutes | Baths/Day | Laundry Loads | Use Temp °C | Heater Temp °C |
|---|---|---|---|---|---|---|
| Small Home | 2 | 7 | 0 | 1 | 40 | 60 |
| Family Home | 4 | 8 | 1 | 1 | 42 | 60 |
| Heavy Use | 6 | 10 | 1 | 2 | 43 | 65 |
The calculator first finds mixed water from each activity. It adds showers, baths, dishwashing, laundry, and sink use.
Mixed Shower Water = Showers × Minutes × Flow Rate
Mixed Bath Water = Baths × Bath Volume
Mixed Dishwashing Water = Minutes × Flow Rate
Mixed Laundry Water = Loads × Hot Water Per Load
Mixed Sink Water = Minutes × Flow Rate
Total Mixed Water = Sum of all mixed water uses
The hot share of mixed water depends on temperatures.
Hot Fraction = (Use Temperature − Cold Temperature) ÷ (Heater Temperature − Cold Temperature)
Pure Hot Water = Total Mixed Water × Hot Fraction
Cold Mixing Water = Total Mixed Water − Pure Hot Water
The energy estimate uses water heating physics.
Energy kWh = Liters × 4.186 × Temperature Rise ÷ 3600
Enter how many people live in the home. Then add daily shower count, average shower time, and shower flow rate.
Enter bath use if needed. Add dishwashing minutes, laundry loads, sink use minutes, and their flow assumptions.
Set cold water temperature, target use temperature, and heater temperature. These values determine the true hot water fraction.
Choose the number of days for your planning period. Press the calculate button to see the result above the form.
Use the CSV button to export the result table. Use the PDF button to save or print the result section.
Hot water demand affects comfort, energy use, and storage needs. A rough estimate often misses real habits. This calculator gives a more complete view. It combines fixture use, temperatures, and daily patterns. That makes planning easier.
The tool measures mixed water first. Mixed water is the water you actually use at taps, showers, and baths. It then finds the pure hot water part. This is important because not all used water comes straight from the heater. Some is cold mixing water.
Temperature changes the result. If incoming water is cold, more hot water is needed. If heater temperature is much higher, less stored hot water is needed for the same outlet temperature. This mixing method is more realistic than simple fixture totals.
Showers often dominate hot water use. Bath filling can also be large. Laundry and dishwashing add more demand. Sink use seems small, but it builds over many short uses. Adding all sources creates a stronger estimate.
You can use the result to size water heaters, compare usage patterns, and estimate heating energy. It also helps when reviewing conservation steps. Shorter showers and lower flow rates reduce daily demand quickly. Better habits can lower both water and energy use.
The result shows daily mixed water and daily pure hot water. It also gives weekly, monthly, annual, and custom period totals. The energy section shows approximate heating demand. These values help with budgeting and equipment decisions.
It estimates daily and long-term hot water use. It also estimates mixed water demand, hot water fraction, and heating energy based on your fixture use and temperatures.
They determine how much pure hot water is needed. Warmer incoming water needs less heating. A higher heater temperature can reduce the stored hot water share.
It shows both. Mixed water is the water used at the fixture. Pure hot water is the amount drawn from the heater before mixing.
The main inputs and outputs use liters. The result also shows daily pure hot water in gallons for quick comparison.
No. It is an estimate. Real systems lose heat through tanks, pipes, standby losses, and operating conditions that this simplified model does not fully include.
Shorter showers help a lot. Lower-flow fixtures also reduce demand. Efficient laundry settings and fewer hot-water sink uses can further cut both water and energy.
Yes. It helps estimate demand. That can support sizing decisions. Still, peak-time demand and recovery rate should also be reviewed before buying equipment.
Laundry machines differ widely. Some use little hot water. Others use more. Entering hot water per load gives more control and better practical accuracy.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.