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Now that I'm looking into home automation, I'm thinking about automatically cutting off the fridge power from 3am ~ 5am. Given that modern refrigerators are well insulated, it should be able to withstand 2 hours of non powered cooling.

If I proceed with this project, will I see a big reduction in my monthly electrical bill?

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Direct data measurements for this project available here: kenmankoff.com/data/fridge –  mankoff Apr 29 '11 at 16:52
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It is likely to end up costing a lot more - in terms of buying a new fridge: diy.stackexchange.com/questions/5990/… –  mankoff Apr 29 '11 at 17:06
    
@Level1Coder, you can save alot of electricity by not having a refrigerator at all. Why do you even need a refrigerator for? –  Pacerier Dec 18 '13 at 7:08

6 Answers 6

up vote 27 down vote accepted

You'd need to run an experiment to confirm this, but I think it would be a false economy.

Even though the fridge is well insulated it will warm up by some amount. Then when it's switched on again the cooling would have to work harder/for longer to bring the temperature back down again probably using the same (if not more) energy in the process.

Let the thermostat do it's job and keep the fridge using a little energy over the 24 hours to keep the temperature constant.

You'll save more energy by opening the fridge less often during the day.

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@ChrisF beat me to it ... was thinking the same thing ... and the repeated powering off and on of the fridge might put a strain on the compressor instead of keeping a low running current on the compressor at all times. It would be more advantageous to look at the energy usage ratings of the existing fridge and consider buying a more eco-friendly fridge. –  Scott Vercuski Nov 5 '10 at 11:03
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And clean the coils. –  aphoria Nov 5 '10 at 11:34
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Exactly right -- at night, when no one's opening the door, it's entirely possible that the built-in thermostat is already giving you 2 hours of compressor idle time anyway. –  Mike Powell Nov 5 '10 at 13:07
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+1, But this only holds true if you pay the same rate during all the day. You might have two-rates payment plan - say N cents per KW-h in the night and 3N cents per KW-h all the other time. Such plans are typical in some regions. If that's the case it really makes sense to shift all cooking (as far as it is convenient of course) and the same would make sense for the fridge - if you shut it off for say four hours before the night rate comes into effect it will then drain the same energy when the cheaper night rate is in effect and that could save you money. –  sharptooth Nov 5 '10 at 14:02
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This answer is wrong and has been proven wrong with scientific studies. It is all about energy conservation. You are comparing cooling things to a constant 35 degrees or letting things sit for a few hours to a possible 40-42 degrees and instantly cooling to 35 degrees one time. Also the emptier the fridge is the more wrong this answer is - a fridge with just a few items makes this dramatically wrong. Now there is a downside - dairy will spoil faster, compressor on fridge might be overworked after but that isn't part of the question. –  DMoore Jun 8 '13 at 6:15

The basic rule:

It takes a certain amount of work to move a certain amount of heat out of your fridge. You can do it now or later, but it's the same amount of work. So the first approximation says you save (or lose) nothing.

Turning the motor on and off takes some energy, but it's pretty small compared to the actual cooling load.

How quickly the fridge loses heat depends on the temperature difference, the insulation, and the skin surface area. So:

  • Letting the fridge be warmer makes its job easier. So does letting your house be cooler. Or putting the fridge outside in the shade during the summer.

  • A modern, well-insulated unit will use less energy.

  • All other things being equal, a smaller fridge will take less energy. Most of what we put in our fridge, our ancestors left in a cool cellar or just on the counter. You could adopt some of those habits and shrink your fridge.

In the winter, I keep my house warm with an electric furnace connected to a thermostat. All the energy that goes in to my fridge comes out as "waste" heat, making my house a little warmer. If I optimized my fridge, then my furnace would just run more to make up for it. So there's almost nothing to be gained, at least during the winter. (In the summer, if you run the AC, then you're paying twice to cool your food!)

I use a Kill-A-Watt to measure the energy consumption of my appliances and computers. It doesn't measure everything (240V items, hard-wired fixtures), but it helped me learn a lot about where my power is going.

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I have a friend who is a serious electonics guy. He has done exactly what is described here. He built a controller/timer that switches off power to his freezer/regrigerator during peak hours (noon to 6 PM). It also shuts off when the temperature reaches 6 degree F; If the temperature reaches 20 degrees F, it switches back on.

He demanded (and got) a time-use electricity meter from the power company, thus he can optimize the price/usuage formula (basically, avoid peak times). He says that he has saved a lot of money, over time. He built his control unit, and measures KW-hours of usage, converted into pricing.

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Welcome to the site. It's best not to post personal information in your answers, so I asked a moderator to remove it. You can have it in your profile if you want (in the about me box) and mention that it's there in your answer. –  Niall C. May 23 '12 at 19:22
    
OK, I have submitted my email address in the profile. I have a very simple mission here: To get my friend's idea about energy savings, with freezers/refrigerators, out there in the public. He is not out to make money. He is willing to provide schematics for free. Please cntact me, if you are interested (especially ChrisF). –  Craig Laughton May 23 '12 at 20:42
    
This "idea" does not save electricity, it saves "money". –  Bryce Jul 10 at 17:16

There is a basic reality that is being missed in several posts on this issue. No matter what energy is being used--gasoline, electricity, wood, coal (or even nuclear)--it takes MORE energy to GET a thing moving, cooling, heating, than it does to KEEP a thing moving, cooling, or heating. If you doubt this basic scientific principle--albeit, stated in layman's terms--just hop on a bicycle, and start peddling. You will quickly find that it is far harder to GET it moving, than it is to KEEP it moving. The same is true for an automobile, and that is why highway travel mileage is so much higher than city travel mileage.

The same principle applies to refrigeration, which includes refrigerators and freezers, as well as air-conditioners. It takes far more energy, that is electricity, to cool something warm, than it does to KEEP cool something that is already cool. I learned this as a small child, from my father, who was a commercial and industrial mechanical engineer, with a specialty in air-conditioning and heating, so it does not take a very experienced adult, with years of education, to understand the basics.

YES, if you turn off a refrigerator you are using less--indeed, NO--electricity, while it is off, but the same thing holds true for an automobile. Next time you are going somewhere, simply turn the ignition key off, and you will be surprised how much gas you save. Of course you will not get very far, but... That is no less true for refrigerators. Besides using MORE electricity to GET the fridge cool again, you will lose much of the health benefits of keeping food much cooler than room temperature. As stated on the FDA Website, "When it comes to protecting yourself and your family from foodborne [sic] illness, one of your most effective tools is the kitchen refrigerator. In fact, at room temperature, the numbers of bacteria that cause foodborne [sic] sickness can double every 20 minutes! Chilling foods to proper temperatures is one of the best ways to slow the growth of these bacteria."

If you are contemplating turning your refrigerator off once or twice a day, for a couple of hours, or all night, and you are doing so because a power company suggested it, consider the source. Do you really think that a power company is concerned about saving you money, or is it perhaps that it wishes to reduce its power demands?

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what if the fridge were to be switched off for the whole night every night? (from about 9 - 6:30). I live in a studio apartment and the noise it makes is annoying to say the least.

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Maybe this would work for those that don't mind having all your frozen food melt and refrigerated food spoil. –  BMitch Sep 11 '13 at 11:46

Switch off the fridge for three hours from 06.30 pm . this will not harm the food stored and will save upto 15percent in consumption.

First of all let me explain the importance of the issue and the benefit to the nation. The country is facing acute power shortage during the evening hours which lead to load shedding in almost all the areas of the country. It is creating difficulties to students, housewives and the public at large. I was suggesting an easy solution to the stalemate with the co operation of the public.

Moreover the peak power costs much to the individual electric supply agencies and hence this solution will reduce the financial burden on them and there by tend to reduce the tariff.

The friends who made the comments unfortunately overlooked the greater national interest and concentrated on the difficulty to individuals.

Anyhow scientific studies and close examination of the technical issues have shown that the concerns raised by my friends are baseless.

The research wing of Kerala State Electricity Board has made detailed research on the subject. It had discussions with experts of different areas including microbiologists. The food materials stored in fridge undergo a cooling process which involves much time depending on the size of the material. At first the surface gets cooled and then it gradually goes to its core. Fish and meat of normal size takes 5 to 7 hours for this. Even if these materials are exposed to atmosphere it takes at least three hours to lose cooling to the core and will take much more time for the bacterial action leading to decay to start.

In the case of switching off the fridge for three hours is much safer. By three hours the temperature rise has been observed to be less than 2 degrees. Hence I can guarantee that nothing will happen to the food materials. On the other hand this time will be utilized by the fridge to defrost the cooling tubes and it will enhance the cooling capacity of the fridge thereby helping to keep the food materials safe for more time. As the phrase “switching of the fridge for three hours during the peak hours” has to be repeated several times let us use the term “Save-switch” hereafter to denote it, as we had done during the research project.

Now let us see how consumption is reduced by save switching. During peak hours the voltage and frequency of the supply will go below the rated values. This will seriously affect the efficiency of the compressor motor of the fridge. Thus the amount of cooling can be done at off peak hours with smaller amount of electricity. We have observed that a saving up to 15 percent can be achieved in the total consumption of the fridge through save switching. At lower voltage and frequency the motor current will be higher and it will reduce the life of the motor. Save switch avoids this and will increase the life of the fridge. Automatic defrosting uses heaters to defrost causing double wastage of precious electricity on for heating and the to remove that additional heat. save switching avoids the need for automatic defrosting thus again helps saving electricity.

Stabliser used with the fridge makes several switching during the peak load because of drastic variations in the supply voltage. This cause inducing of high voltages in the inductive circuits of the motor and agin it affects the life of the motor which can also be avoided by save switch.

Thus we can see that save switch helps the country to face the power crisis and helps the consumer through saving in consumption and increased life of the fridge. I am ready to clear any more doubts on this.

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