Tank Capacity (Liter) Selection

Selecting the correct storage volume is one of the most important design decisions in electric water heater engineering.

Improper sizing leads to:

Tank capacity must be determined based on hot water demand profile.

1️- Domestic Hot Water Demand Estimation

The required tank volume depends on:

Typical hot water consumption per activity:

Shower : 30–50 liters

Hand wash : 3–5 liters

Kitchen sink : 10–15 liters

Bath : 80–120 liters

A simplified engineering estimation:

Vt=Vu * (Tu−Tc) / (Tt-Tc )

Vu=N*Ve

Where:

This formula accounts for mixing between stored hot water and incoming cold water.

Using the formula:

Vt=Vu * (Tu−Tc) / (Tt-Tc )

Vtank Vt = 120 * ( 40-20 ) / ( 70 -20 ) = 48 Liters

very simple formal function of N if we assume other parameters as above .

Vt = N *Ve (Tu−Tc) / (Tt-Tc )= N*40*(40-20)/(70-20)

Vt = N * 16

if N = 3 then Vt = 3*16=48 Liters

So: 👉 A 50 L water heater would be appropriate.

1 Person : 30–50 L

2 Persons : 50–80 L

3–4 Persons : 80–100 L

5+ Persons : 100–150 L

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