When we get our electricity bills, it shows that we have used a certain number of units for the given period. When we go to buy appliances, most of them have watts mentioned on them. If you find it difficult to understand the relation between the two, then you are not alone. Electricity bill and its components are confusing to many and with this article we will try to explain what are watt, kilowatt and a unit of electricity. Power and Energy/Electricity are two words that are used so much for each other that many feel that they mean the same. Interestingly both of them have a very different meaning. Power is the rate at which electricity is used and energy/electricity is the actual consumption. To give an analogy, power is similar to speed but electricity/energy is the actual distance travelled. So        Power x Time = Electricity (or energy) Just like          Speed x Time = Distance Travelled. Power is always represented in watt (W) or kilowatt (kW).

A thousand (1000) watts make one kilowatt. So if any appliance is rated as 1.2 kW then it means that it consumes electricity at a rate of 1200 W. Now as we discussed earlier that power is the rate at which electricity is consumed and not the actual electricity consumed, Watt or Kilowatt just represent the rate at which electricity is consumed per hour. Which means that when you buy a 100 W bulb, it does not consume 100 units of electricity but consumes at a rate of 100 W.precision air conditioning unit catalogue A unit (as mentioned on the electricity bills) is represented in kWH or Kilowatt Hour. jeep cherokee air conditioner compressor clutchThis is the actual electricity or energy used. car air conditioning repair bolton

If you use 1000 Watts or 1 Kilowatt of power for 1 hour then you consume 1 unit or 1 Kilowatt-Hour (kWH) of electricity. So the reading on the electricity meter represents the actual electricity used. Just like the odometer on your vehicle that shows the actual distance travelled by the vehicle, electricity meter shows the amount of electricity that is used. So a 100-Watt bulb if kept on for 10 hours will consume: 100 x 10 = 1000 Watt-Hour = 1 Kilowatt-Hour (kWH) = 1 units (on your meter). Now with most of the concepts explained we would like to make it easy for you to calculate how much units does any appliance consume. Most appliances have wattage written on them (either on their container box or somewhere on the appliance). Once you have the wattage, next you need to figure out how many hours a day do you use it. After that you can use the formula below: Daily Units = (Wattage x Usage hours per day) ÷ 1000 Monthly Units = Units x 30 (or 28,29,31 based on month)

Please note that this formula may not work always. For appliances like Air Conditioner, Water Heater, Cloth Iron (any heating or cooling device) and pumps, this will not work. Also check this video that can help you understand how many units your appliances are consuming:It’s peak summer, and one thing that worries most people is: electricity consumption by air conditioners. No wonder, while buying air conditioner, people look for the most energy efficient ones, as air conditioners can bloat the electricity bills quite easily.  Although buying an efficient AC does help, there are more things that impact electricity consumption of an air conditioner while one uses it. While going through an interesting research paper on IIT Madras website we stumbled upon this interesting concept of looking at what impacts electricity consumption in air conditioners, which resulted in this article. Listed below are things that impact electricity consumption: All ACs are rated in watts, but they do not consume the same all the time.

Most 1.5 Ton ACs are rated for about 1.5 kW to 2 kW. But their consumption varies in different settings. The job of an AC is to remove heat and humidity from and enclosed space and it will consume just that much amount of electricity that is required to do so (plus or minus delta based on AC sizing). Which means a 1.5 ton AC if put in a 120 sq ft room will consume different amount of electricity in one hour than a similar AC put in 150 sq ft room in the same location (and in similar conditions). This is because heat will be more in 150 sq ft room and thus it will take extra electricity to remove it. Some cities are hot; some are humid and some cold. An air conditioner does 2 things: cool the air and remove the humidity. If a city is hot, most of the electricity is consumed to bring down the temperature. But some cities are humid but not very hot (costal regions) and because the switching of the compressor depends on temperature. So a 1.5-ton AC in a similar setup in 2 cities will consume different amount of electricity because the temperatures are different.

The consumption will be less in the city with lower temperature. This also brings up a point that the tonnage of AC required for a room varies across cities. A city that is more humid does not require much cooling but needs more of humidity removal. Humidity removal depends on the time for which compressor runs. If the AC is oversized, compressor will run in short cycles and thus will not be able to remove humidity effectively. Thus it makes sense to buy smaller ACs for a humid place. On the whole sizing of air conditioner is important. From colors in the room, we don’t just mean the color of the walls. All dark colors absorb heat. So if your curtains are dark, they do not help. If your walls are dark they absorb heat. Even if you the cloths you are wearing in the room are dark, they absorb heat and will take more time to cool. If everyone in the room is wearing dark jeans! it means your AC is working harder. Most of these things are unavoidable, but some of it might help if you are aware of it.

Recently a friend called us up regarding electricity bills in his coaching classes. On evaluation we realized that he had 2×2 ton ACs in a small room of 150 sq. ft. and both had to be kept on when the classes were on. A class full of 40 kids had so much heat that it needed so much cooling. Human body emits heat based on its metabolic rate. Thus more the number of people, more is the heat in a room and thus more cooling is required. This if more people are expected in a room, more tonnage is required to cool the room. We often observe that our laptops or computers become after long operation. Even mobile phones behave the same way. All electronic and electrical appliances emit heat that will be cooled if Air Conditioner is turned on. Even bulbs and lights emit heat along with light (more on it on our article: ). Thus if you put a lot of lights in a room, the room will need more air conditioning. Thus using lesser lights will have double benefit. A warehouse full of material typically needs a lot of air conditioning, because every object kept in the space needs cooling.

Every solid object is a conductor of heat and thus more the number of things in a space, more is the cooling required. Keeping a room organized thus makes much more sense not just for aesthetic beauty of a room, but also for air conditioner’s electricity consumption. Keeping things in closed almirahs can thus reduce some electricity used by an air conditioner. The walls also absorb heat and thus insulation of walls is important. And now a few things that we have already covered in previous articles: In our article on Ideal Air Conditioner temperature for electricity savings we wrote that the electricity consumption of air conditioners depends on the thermostat temperature. The lower you keep the air conditioner temperature; higher will be the electricity consumption. In point 1 we talked about size of the room impacts electricity consumption. It essentially means that the space to be cooled is more in a bigger room that needs more electricity to be cooled. In a previous article: , we pointed out how if the doors and windows are not closed, the space to be cooled increases.