DIY, Super-Efficient Fridge Uses .1 kWh a Day

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by Tim Fulton on December 1, 2008

You know the cool feeling on your feet every time you open the refrigerator door? If you didn’t know, that’s the feeling of all your cold air falling out on the ground. Cold air is heavy and naturally sinks down, which makes the design of most refrigerators suboptimal for conserving that cold air when opened. Though convenient, this means that your refrigerator will be using a lot more energy than is necessary.

Well, what can you do about it? In Japan there are refrigerators with pull out drawers that help eliminate some of the problem, but importing a massive Japanese appliance isn’t likely to happen for most of us. Luckily, there is a DIY solution that involves converting a deep freeze into an incredibly efficient refrigerator chest.

You can check out the DIY PDF here, but in summary, what the creator, Tom Chalko, did was get a chest freezer and modify the temperature control so that it held foods at the normal temperature a standing refrigerator would. In the end, Tom had a fridge with a slightly non-traditional organization of foods, but one that only used about 100 watt hours of power a day, compared to most refrigerators, which use between 1 and 2 kilowatt hours per day. If you’re interested, be sure to check out the PDF for some more specifics.

Also, check out our article on a DIY Passive Cooled Fridge, and our series on DIY improving your freezer’s efficiency.

{ 9 trackbacks }

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{ 41 comments… read them below or add one }

1 John Clemence July 13, 2009 at 2:13 am

Any idea where the thermostatic switching can be sourced – the plug in device mentioned earlier in this post would not work as it senses room temp not temp of fridge.
John

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2 Chris August 11, 2009 at 12:31 pm

Google “johnson controls refrigerator thermostat”
around $60.00 est.

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3 Jeff August 12, 2009 at 12:37 pm

When I was a kid we had a US-made slide-out freezer like the Japanese variety mentioned. It was a style-thing (possible ergonomics for fat folks) during the 70s to have the freezer side-by-side. We used to be smarter: more energy efficient and free exercise when you reach for the ice cream.

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4 Ben August 13, 2009 at 1:38 pm

What about a freezer? To make this work you’d need to spend $400 buying at least a 5 cu ft fridge and 5 cu ft freezer. You’d have 10 cu ft of space. If the fridge uses half the power of the freezer mode, based on the energy tags that are on these, the fridge would cost $12.50/yr and the freezer $25 for a total of $38 for only 10 cu ft of space. On the other hand a $400 upright fridge/freezer combo is 18 cubic feet (almost twice the size) and uses $39 per year worth of power (numbers come from energy ratings at lowes.com).

Not to mention the fridge unit would probably break down much sooner due to the constant switching of power. This sounds impractical.

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5 Chris August 13, 2009 at 4:21 pm

Ben

Thanks for the cost comparison.
The $25/year cost on the freezer would be reduced by the run time. I have seen min run times on large compressors. A timer could be integrated to protect the compressor from overheating. My upright freezer cuts on and off for as short a 1 min. I imagine if the min run time has been engineered out of the equation to reduce elctrical cost from the mfg. A thermal switch could be integrated as well.
The larger your refigeration needs the larger freezer you obviously need. The larger the freezer the electrical eff% goes up on some scale. When this tread was started I looked for a small Chest type freezer just for Drinks/Snacks. I wanted to start with a small Energy Star Rated freezer. When you look at the Sears/Lowes type stores the EStar Freezers are larger than my needs.

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6 John S August 13, 2009 at 6:22 pm

“A typical household refrigerator uses about 2 KW-hrs/day of energy. That is about 7% of household electrical usage. Many have two refrigerators, which means 14%”

Actually Steve, doubling the raw value does not double the percentage.

(Example: 2 kWh is 7% of 28.57 kWh. Adding another 2kWh/day fridge would bump the household daily power consumption to 30.57 kWh. Thus the two fridges would combine to 4kWh/day, or 13.08% of the household electricity bill, not 14%.)

It doesn’t change your point, however. :-)

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7 Chris August 13, 2009 at 7:52 pm

I checked out that $400 Refigerator at Lowes. Annual cost $41.00

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8 Chris August 13, 2009 at 7:55 pm

My Bad $41 for 9.7 cf $43 for 18 Cf

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9 Ben August 13, 2009 at 8:00 pm

The one I looked at was item # 144787 which is $39/year (also 17 cu ft), though a difference of a couple dollars a year or a single cu ft is really splitting hairs. It still stands that overall this isn’t a good deal unless you can get by with only a fridge and no freezer. I know that I can’t.

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10 Chris August 13, 2009 at 8:35 pm

I can’t live with out a freezer either.
I have both an upright refigerator and a Chest Freezer. Excuse the run on sentences and spelling.
Lets say my old 13 CF chest Freezer cost me $34.72 a year and my Refigerator Cost me $39.23 a year. Your Looking at $74 a year. I Spent say $400 ea for a total of $800.
Maybe I could get rid of both and purchase a New Amana 25.1 cf from sears Model ABB2522FEB for $1,232.49. This is the most eff. refigerator that I can find from sears with a KWH/Cubic Foot rating of 18.92 or annual cost of $50.59. Great Deal.
Or I could purchase a Kenmore 24.9 CF freezer for $722.49 with a 20.56 KWH/CF rating reduce the run time from est 30 min/hour to est 3 min/hour with an anual electric cost of $5.45. I could keep my old Chest freezer or purchase a new one. If I purchase a new 13 cf chest freezer and the 24.9 cf freezer I will have 24.9 cf of refigerated space and 13 cf of freezer space for $1104.98 and my annual electric cost will be $40.17.
What have I gained by modifing a chest freezer vs. purchasing a new up right. Well I saved $127.51 -$60.00 for the Thermostat Control. Saved $10.00 a year in electricity and I gained 7.1 CF of refigerated space and 5.7 CF of Freezer space. If I compare the savings to what I have right now I will save $35 a year in electricity and still gain about 6 cf or refigerator space.

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11 Chris August 13, 2009 at 8:42 pm

Ben

I was not trying to call you out I did not read your post correctly I thought you stated the 18 Cf upright has an annual cost of $12 my bad again. Somebody might want to recheck my math :-)

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12 John Clemence August 14, 2009 at 1:54 am

Hi,
Comparing price for running fridge and freezer is a good measure for establishing power used while I assume most comparisons are for equipment running grid mains voltage, I am more interested on “off grid” values – I have a holiday home with no mains power and got by with 100 watt solar panel with an inverter for lights, radio & tv and had a caravan gas fridge which has now died.
I am looking at what to replace the fridge with, I could get another gas one but my wife is rather reluctant, (after the last one leaked gas). I could buy a 12 volt (compressor?) fridge and I thought I could get another 100 watt solar panel & battery – would 100 watt be enough for just the fridge? or another thought was to get a mains powered fridge and run it off the new solar panel via an inverter.
I have also thought about converting a chest freezer into a fridge as mentioned on this list. Does anyone have any experience on this, 12 volt compressor fridges are very expensive – do fridges and freezers run off cheap inverters? are the freezer converted fridges really that much more efficient?
Any input most welcome.
Regards,
John.

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13 jonny August 22, 2009 at 2:57 am

I run a Vitrifrigo 12v compressor fridge, 2 100w panels, 2 golf cart batteries, and a 25 amp charge controller in my motorhome. I have converted the interior lights to LED style, I have a small 500w microwave , and an 600w constant / 1200watt surge inverter.

System keeps the batteries fully charged even when not moving for one week.

Regards
Jonny
Sonoma California

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14 jonny August 22, 2009 at 2:59 am

I meant an 800w constant / 1200w surge inverter

Jonny
Sonoma California

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15 Chris August 14, 2009 at 8:46 am

John Clemence

A 200 watt solar panel array will keep a bank of batteries charged. Batteries can get exspensive esp. if you need a charger/transformer. The KWH demand, full load amps and run time of your refigeration needs would determine the size of your battery bank.
I think you need to know the size refigerator you need to come up with your electrical load. Im interested in your plans!

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16 Chris August 14, 2009 at 10:02 am

John Clemence

I’m guessing your caravan fridge was in the 3 to 8 CF range. Check out this thread.

http://www.fieldlines.com/story/2007/4/24/161341/327

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17 jackson | [url=http://www.websecuritysysetms.co.uk/]alrams[/url August 28, 2009 at 5:38 am

I believe that the eco-efficient wave nowadays is totally self-indulgant, every new technology, every new latest thing, is just a selfish -self-promoting, improving way for western society to become happier, whilst all our time and effort is devoted on this, about 0.03 % of our weekly thoughts and efforts are about the 3rd world. Donating £3 a month to a charity is going to be a drop in the ocean. We need to be investing billions a month into all the African nations to give them food and water and to re-educate them so tyrannical leaders do not take charge in government and ruin the country.

0.03% of your weekly thoughts are on 3rd world thousands dying.

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18 EllisGL August 28, 2009 at 8:45 am

How about the kids that are dying in our own country?

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19 jackson | [url=http://www.websecuritysysetms.co.uk/]alrams[/url August 28, 2009 at 5:39 am

Very nice idea, would love to see it in action.

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20 lala April 30, 2012 at 12:46 pm

Learn new eating habits. Learn to live without a effing fridge! Started it a yr and 1/2 ago and am blown away how easy it was. Now have 2 big barrels on my roof which the sun heats and it does all my dishes and bathing with lots left over.Many things you can do. 2 ie’s, use milk?? use powered. Eat eggs? They don’t need a fridge. look it up. Eat more veg period!! And get off the meat!! Look that up and see what raising and killing poor animals does to the planet!! EDUCATE YOURSELVES!!…..have a nice day now,,,,ya hear

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21 Swamp thing September 5, 2013 at 9:33 pm

My usage is very important. When you look at a conventional ‘energy star’ unit you will find the consumption for a year is at least 200-500 kwh. My 16 panel solar system produces 1000 kwh per year. That would be almost half of my production from solar.
Within 100-150 kwh per year, it becomes feasible to have refrigeration. Major problems are with the limited insulation. Why dont they just add another inch so you dont have to? And the position of the compressor and condenser coil. Why on earth would you put in under the fridge? Put it on top like in the old days and the heat goes in a direction that does not affect the fridge. Putting it under just transfers all that heat it just removed right back up towards the fridge. Some things just arent rocket science. If you want to get really chic put two compressors on the unit and one is outside. In summer, valves like a heat pump valve put all the heat outdoors and in the winter, indoors to help heat the house.

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