The image above is not our own. See here for original.
In a previous article we touched on the concept of non-linear electric loads (referring to the microwave). We (unfortunately) have a great example of where this occurs and what it means, both environmentally and financially.
Many electrical items in our lives have an equipment rating in watts, which is volts x amps. This is an old-fashioned and somewhat mis-used term that doesn’t show the entire demand of some electrical loads. When you measure non-linear loads (e.g. CFL bulbs, pumps, TV’s, stereos) you must also account for power factor. Power factors affect the amperage that equipment uses. The lower the power factor, the more amperage it consumes – i.e., power. This means you can’t always rely on dividing the wattage rating by the voltage rating to determine the equipment amperage. Since your power meter uses amperage and voltage to calculate your energy consumption, Nova Scotia Power still has every electron accounted for.
In my ‘man-space’ I have a perfect little beverage fridge. It’s cold and it fits perfectly under my workbench (readily accessible for beverages during power tool operations…)
My mini fridge has a listing of wattage, with a rating of 136watts. This unit operates at this energy consumption consistently, 24hours a day.
According to the wattage rate on the fridge, THIS IS WHAT WE GET:
0.136kilo-watts x 24hours = 3.25kWh/day (yikes! This is already quite a bit of power.)
Financially, this would suggest that it’ll cost $0.47/day, $3.27/week, $13.09/month to run this mini fridge. But keep reading.
(BTW, when calculating the cost of electricity, don’t forget to add the 15% tax! Your $0.125/kWh should be $0.1438/kWh. Oh, and the new rate hike takes effect in the New Year – happy holidays!)
BUT: My Kill-A-Watt meter verifies that my mini fridge has a volt-amp rating of 226volt-amps (the amperage and voltage will be listed separately and should equal this value if multiplied – which doesn’t equal the nameplate wattage).
If we use the actual operational values of the mini fridge, THIS IS WHAT WE GET:
(Remember, consistent operation for 24hours a day)
0.226 kilo-watts (volt-amps) x 24hours = 5.5kWh/day (!!!)
Financially this means the mini fridge actually costs us $0.79/day, $5.54/week, $22.15/month!
This is a pretty significant difference from what the mini fridge’s wattage list would indicate.
By comparison, our (older) full-size family fridge with top freezer uses 1.5kWh/day (actual value measured by the same Kill-A-Watt meter). This equates to $0.22/day, $1.51/week, $6.04/month.
So my mini fridge uses almost 4 times as much power as our regular fridge. And it costs me the equivalent of a case of beverages every month I use it…how ironic! Bear in mind that I only want it for the hot months…this year should be cheap. Next year my conscience probably won’t let me use it.