kW vs kWh
Whether or not you are a student of physics, especially electricity, it is prudent to know the difference between Kilowatt and Kilowatts hour. Maybe you are not interested, but what if you were told that these are concepts related with the power (read electricity) you get from the electricity department and the amount of electricity you consume (read the payment you make). Interested? Read on to know the differences between kW and kWh.
If you understand the difference, and the relation between kW and kWh, it becomes easier to make energy calculations as also saving on energy. Let us first take a look at kWh, which is a unit of energy. This is however not the only unit of energy and we also have BTU, calorie, Joule, also watt hour. There are even some that most of us even haven’t heard of, but we really do not need any other unit apart from kWh for our purposes. It is like describing a distance in feet, meter, km or miles depending upon the unit with which you are most comfortable. But, all units of energy are convertible into any one that you prefer. Even a cookie that gives us a few calories means it can be converted into kWh unit (though it is impractical to do that).
What is kW then? It is the rate at which energy is produced or generated (in reality, electricity is not produced; it is rather converted from one form into another). kW is a unit of power, and if you have an air conditioner that has a rating of 2 kW, all it means is that it consumes 2kW or 2000 watts of energy per hour. Kilowatt describes the energy consumption rates of an appliance, and higher this rating, more expensive is the running cost of that appliance. If you have a 100 watt bulb or a fan, what it signifies is that it will consume 1 kW of electricity or power, if you keep it running for 10 hours. (100 watts X10 = 1000 watts or 1 kW).
It is clear then that the relation between kW and kWh is the same as that between power and energy. The rate at which work is performed is power, whereas energy is the capacity to perform. Multiplying kWh (energy used) in your bill with the rate charged per kWh by Electricity Company gives the amount you are required to pay to the company. Let us understand this with a practical example.
Let us assume the Electricity Company in your area charges 10 cents ($0.10)/kWh, and you are using a room heater to beat the chill. This heater has a rating of 1.5 kW and you use the heater for an average of 8 hours a day. This means that you are using up energy to the tune of 8 X 1.5 = 12 kWh. Just multiply this with the charge that is $0.1 and you get a figure of $1.2. Now you know that your heater is costing you $1.2 per day, and in a month it is eating up 30 X 1.2 = $36. Similarly you can calculate how much all the appliances are costing you in a month, and accordingly draw up a saving plan to start on electricity saving.