Home Energy Saving Blog

Since ‘The year of the Fridge’ appeared in The Times on Sat 5th Jan, we have had a number of emails asking questions about how to best use the Plug-in Consumption Monitor with a fridge or freezer, what results to expect and how to translate that into running costs.

Feel free to ask any questions / make any comments at the bottom of this entry, no need to register or anything. All questions will be answered.

How Fridges & Freezers work

Fridges use a thermostat to control the temperature. When the temperature inside the fridge becomes too warm the cooling mechanism is switched on until the temperature is lowered and the thermostat switches the cooling system off.

Throughout the day the fridge constantly cycles on & off to maintain the temperature.

How to use the Plug-in Power Monitor with a Fridge / Freezer

If you look at the bottom half of the Plug-in Consumption Monitor page, you’ll see the various modes the meter has. Two of the modes are of interest to us here:

Mode 1 - Wattage Display

This mode will tell you how much power (in watts) is currently being used. It’s great for measuring anything that draws a steady current such as a TV / DVD / Freeview etc on standby but not ideally suited to a fridge or freezer.

If you were to use this mode on a fridge you would see it spends lots of it’s time using little power at all and some of it’s time drawing maybe 100 watts or so when the cooling system does switch on.

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Blackle.com is just Google on a black background. So simple.

The claim is that a Black Google would have the potential to save 750 megawatt hours of electricity per year by simply not being white, based on the theory that it takes less energy to display black images than white images.

To quote from the blackle.com website:

Blackle saves energy because the screen is predominantly black. “Image displayed is primarily a function of the user’s color settings and desktop graphics, as well as the color and size of open application windows; a given monitor requires more power to display a white (or light) screen than a black (or dark) screen.” Roberson et al, 2002

So, armed with our trusty Plug-in Electricity Consumption Monitor we set out to do a few tests on the power required to display a white screen and a black screen on 2 different types of display.

Test 1: JVC 26″ CRT television (5 years old) Black Image: 59 watts White Image: 107 watts

Test 2: Dell 19″ LCD monitor (3 years old) Black Image: 24.3 watts White Image: 21.7 watts

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