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The differences between Power (Watts) and Energy (Kilowatts-hour, kWh)

Before you can start saving money by cutting cost on unnecessary electricity usage in an attempt to live a greener life (Essential tips to start living Green today), you need to understand Power and Energy and the units of power (watt) and energy (kWh), what they mean, how do you use these terms etc. I have tried to give a high level explanation on the differences between watt and kilowatt-hour (kWh). Feel free to add your thoughts through the comment are below.

What is Power and Energy?

Simply put, Power is the rate at which work is performed or energy is transmitted. Energy is the capacity of a physical system to perform work.

What is the difference between Watt and Kilowatt-hour (kWh)?

Watt is the unit of power whereas kilowatt-hour (kWh) is the unit of energy.

Watt indicates the rate of using energy in J/s. You can compare this to how fast water is flowing out of a water pipe. If you have a Light bulb that has a rating of 100 watt, it means that the light bulb consumes 100 J per second.

kWh is the unit of energy. You can compare this to the volume of water that comes out of the pipe. A 100 watt light bulb when used for an hour will consume 100 Watt-hour of energy which is 0.1 kWh of energy.

If you multiply the total energy usage kWh with charge per kWh (This should be on your electricity bill), you get your total Electricity cost.

Watt and Kilowatt-hour (kWh) practical example

  • Your electricity provider charges you 11 cents ($.11) per kWh.
  • You have an Electric Heater that consumes 1500 watts (1.5kw). You use the Electric Heater for 3 hours everyday.
  • For 3 hours it will cost you 1.5kw x 3hours = 4.5kWh x .11 = .495 cents (50 cents)
  • Over a month it will cost you .495 x 30days = $14.85

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