Power requirement to heat water

[hohe]

What is the power required in watts, to heat 200 litres of water from 5c to 60c.

[New Forester]

What you are asking is for energy, rather than power. The power required also depends upon the time it needs to take. So first find the energy needed, in joules. The specific heat capacity of water is 4.187 KJ/Kg/K. That means it takes 4187 Joules to raise one kilogramme one degree Kelvin. One kg of water is the same as 1 litre; 1 degree K is the same as 1 degree C. The rest is simple arithmetic, which I'll leave you and your calculator to do. One watt is one joule per second. From that you can work out the watts needed to achieve your temperature rise in whatever number of seconds you like.

[hohe]

Many thanks for your answer. I am working on a micro-hydro power project and trying to work out if I will have enough energy to heat the water as well as run the house. Great help, thank you.

[hohe]

New Forester, just one more question. After working out how many Jules are required to heat 200 Lts by 55C (46.057.000), and using a 3KW boiler, do I divide the figure by 3.000 to come to the time required in seconds? Thank you. Hohe

[Tweed]

Yes. Every second will use 3000J, you require a total of 46057000J so it'll take that value / 3000 to get the time in seconds (divide by 180000 for time in minutes).

[Tweed]

...if working in joules.