I have to program a relatively simple program so I can display values on dashboard representing the part kWh a system is responsible for generating. This will be represented as a percentage.

I have a known value -> total generated cooling in kilowatt-hour.

I have 2 cooling machines where I had to calculate the required power to cool a medium (water) resulting in a kilowatt value.

Using this formula (energy required to heat or cool a medium water in kW).

How do I convert the resulting kW value to a kWh value so I can calculate the fraction of cooling my machine A or B was responsible for?

I wasn't able to figure it out using google, so any help would be greatly appreciated!

  • 1
    \$\begingroup\$ what's difficult about multiplying by time? \$\endgroup\$
    – user16324
    Commented Aug 26, 2022 at 15:12
  • 1
    \$\begingroup\$ How do I convert mph to miles? I have a known value -> distance to travel in miles. I have 2 cars where I had to calculate the required speed to travel a road resulting in a mph value. How do I convert the resulting mph value to a miles value? \$\endgroup\$ Commented Aug 26, 2022 at 16:36

2 Answers 2


How do I convert generated cooling capacity in kW to kWh?

  • 1 kW generated or consumed for one hour is an energy of 1 kWh

  • 2 kW over 30 minutes is an energy of 1 kWh

  • 0.5 kW over 30 minutes followed by 30 minutes at 1.5 kW is an energy of 1 kWh

  • In joules it's 3.6 MJ.


Your formula \$P = m*c*\Delta t * 1/3600 \$ is complete nonsens, if you interpret the symbols in your way.

I haven't found a good Web site for that so far (only https://sciencing.com/calculate-time-heat-water-8028611.html) but this site seems to be unscientific...

In fact, to cool (or warm) liters of water, the following equation can be used: $$ E = c \cdot m \cdot \Delta T $$ If you handle with pure water (not ice, nor H2O gas) the specific heat capacity \$c\$ is about \$4.19\,\frac{\textrm{kJ}}{\textrm{kg K}}\$. The \$m\$ is the mass of the water, and \$\Delta T\$ is the temperature difference in Kelvin (i.e. the temperature difference from starting point to the end point in degree Celsius). Because the density of water is about 1 g/cm3, mass and volume correspond. The volume of 1 liter of water corresponds to the mass of 1 kg.

So you will get the Energy \$E\$ in Kilojoule (kJ) which is equal with: $$ 1\,\textrm{kWh} = 3600\,\textrm{kJ} $$ To calculate the kWh, you can simply divide the result (given in kJ) with 3600 and \$E\$ becomes the amount in kWh.

To calculate the power \$P\$ for a period of Time \$t\$, use $$ E = P\cdot t $$


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