Water Heater Calculator, Formula for Time Required to Heat

Water Heater Calculator:

Enter the water quantity in litre, initial and final temperature in degree Celsius. Then press the calculate button to get the power required to heat the water in one hour.

Enter Water Quantity: Liter
Initial Temperature: Celcius
Final Temperature: Celcius
Required Heater Capacity:

Water heater Calculation:

Water heater power P(kW) in kW is equal to the 4.2 times of the quantity of water L in Liters and the temperature difference divided by 3600. Hence, the required power to heat the different temperature formula can be written as,

P(kW) = 4.2 x L x (T2-T1) / 3600

T1 = Initial water temperature

T2 = Final water temperature.

From the above formula, we can calculate the net kW required to heat the L qty of water. For calculating Time to heat the water, the formula can be,

Time required = P(kW) / Heating Element capacity in kW


Let we take an example of 10 Liter water temperature to be raised from 25 deg to 70 deg. Calculate the kW required for heating the element, here we have 4.5kW heating element in our hand. Calculate the time to heat the water.

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P(kW) = 4.2 x 10 x (70-25) / 3600


It requires 525 Watts heating element on one hour.

But you have 4.5kW heating element, then

Time required = 0.525/4.5 = 0.12 Hours [7 minutes].

In 7 Minutes, you can heat the 10-litre water from 25 deg to 70 deg with 4.5kW heater.



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