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Name: Steven
Status: student
Age: 30s
Location: N/A
Country: N/A
Date: 1999 

I am working on a project for a Marketing 230 at Elmhurst College. I need to know how a kilowatt is consumed. I also need to know how a kilowatt is metered and billed. How would a grocery store go about lowering their electricity usage cost?

Connoisseurs will insist that a kilowatt be gently decanted and allowed to ``breathe'' for up to 30 minutes at room temperature before being consumed, but regular folks would tend to chug it straight from the fridge, without even bothering to pour it into a clean glass, and will assert that the flavor is in no way compromised thereby.

Oops. Sorry about that.

Wouldn't it make sense to drop in on a neighborhood store and ask the manager these questions? They might be delighted with your interest, especially if you offered to make some detailed analysis for free and give them the results to use as they see fit. Just a thought.

Electricity is metered by measuring the current through a motor installed outside the store in a little glass case. As more current flows, the motor runs faster and it makes the little numbers the meter reader records advance faster. It is billed by the kilowatt-hour, with one kilowatt-hour being the amount of electricity used by a 100 watt bulb in 10 hours.

Personally, I'd guess a grocery store consumes most of its power in refrigeration, which is an inefficient process, especially if you leave off the doors of the refrigerators and/or pesky consumers keep opening and closing the doors for no better reason than buying the merchandise. You could reduce the power consumed by installing doors or flexible plastic flaps over the refrigerators to keep in the cold air, or by facing the doors straight up (cold air is heavier than warm air). In frigid parts of the world you could perhaps chill by using ambient air, sometimes. That would involve a lot of capital expense that seems unlikely to be recovered fast. You could also perhaps buy electric power at off-peak rate times and use it to chill water. Then you could refrigerate during peak rate times with your cold water.


First of all, the measurement used by electric companinies is generally the kilowatt hour, which means that you used 1000 watts of energy for an hour.

This electrical energy is used for any electrical device that is used by the store. This includes lights, heaters, air conditioners, registers, scanners, etc.

Each device consumes energy at a different rate, and adds to the total amount of energy used.

Lights are generally given a wattage that tells you how much energy they use. For example, if you have 10, 100 Wat light bulbs on for an hour, that will use 1 kilo-watt hour of energy.

Some devices measure the power they use in Amps. That can be converted to Watts by multiplying the voltage and the amp rating. For example, if you have a 5 Amp motor which operates a saw and runs on 110 Volts, it uses 550 Watts of energy, and would use a kilowatt hour up in an 1 hour, 50 minutes.

Other devices may measure their energy consumption in horse power, and you may have to convert that to watts--1 hp is equal to 746 watts.

So, to determine how much energy something in the store uses up, find out how many watts of energy the device uses, and multiply that by the number hours it is on during the month, and then divide by 1000 to get kilo watt hours.

Obviously doing that for every device in the store would be a time consuming process. But, generally, heaters, lights, motors, scanners, printers, copiers, microwaves, stoves are high-energy consuming devices.

The light company attaches a meter to the incoming power meter to the store. This meter measures how much electricity passes through it and turns faster when more energy is flowing, which sets some dials. This works very much like your car odometer. Each month the power company records the number on the meter, and subtracts the current number from last months to figure out how many kilowatt hours were used.

Then, based on how many kilowatt hours used, they will bill you. Usually the cost is about 6 cents per kilowatt hour.

Hope this helps.

--Eric Tolman

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