All day long, and throughout the night we have electricity working for us in so many different ways. We can purchase it from the power company that delivers it to our meter. Alternatively, we can buy ‘canned electricity’ in batteries. The rate with which we consume energy determines our electrical energy cost. An appliance power rating tell us how much electricity it uses.
How Appliance Power Ratings Work
Power equals the rate at which the appliance does its work. Thus we can expect a higher-rated vacuum cleaner to soak up the dust faster.
However, this benefit does come at a disadvantage, because we are using more electricity that we pay for. Thus, we need to set off the extra benefits against the added cost.
Take a corded electric drill for example, as opposed to a cordless rechargeable one. If we just plan to do a few light jobs around the house, then one with a 500-watt power rating should do the job. However, we will need a more powerful one if we want an effective hammer action to drill through concrete.
Using a Power Rating to Calculate Consumption
Let’s say, for example we want to find out the annual operating cost of a desktop computer with flat screen. The one we are considering purchasing has a power rating of 80 watts.
We plan to use it at night to surf the internet for three hours, and we will do this every day except Sundays because we keep the time for our family.
The formula we use is [hours of daily use]times [number of days a year]times [power rating]. Our answer is [3 x 312 x 80] / 100] = 74.8 kilowatt-hours a year. We can convert this to dollars according to the actual kilowatt-hour rate we pay.
We could lower this cost significantly by allowing the computer to go to sleep while we are helping the kids with their homework. The lower power rating could reduce the electricity cost by up 95%, depending on the system design and settings of the device.
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