Five Percent: Conserve Energy

Climate Change Is Important: Energy Conservation is the First Step

December 13, 2010

Why Is My Refrigerator Running When It’s Colder Outside?

Category: Economics,Household – Tom Harrison – 12:02 am

Steam Heat

Baby Its Warm Outside

Last week, it was colder outside than the temperature inside my fridge and freezer … but the fridge kept running — why can’t it use the cold air from outside? And while I am asking questions, why do I need a humidifier in winter while exhausting that nice, hot, humid air from our showers outside with a fan? Or, that nice hot humid air from the dryer — big plumes of hot air into the icy cold? It smells nice, too.

Our homes and their appliances are dumb as stumps. Or, is it us?

To be sure, the bathroom exhaust fan is not a simple problem — there are indeed times when that which is being exhausted is, um, best left outside.

But the clothes dryer — if you put in a dryer sheet, you’re sending nice smelling, warm, humid air outside (and, by blowing air outside through one hole, it is replaced by sucking in cold, dry, outside air through some other leak or hole). The fridge is even more perverse: 20°F outside, and the motor is running? Huh?

Afraid To Be Too Smart

Of course the reason for these inefficiencies is simply that adding smarts to appliances increases complexity, and that increases cost.

Making my dryer do the right thing would require a humidity and temperature sensor, a relay, and a servo motor plus some additional ducting, and most likely some other smarts that make sure mold isn’t building up. A heat-exchanger on the vent pipe might be a start.

The fancy fridge that uses cold air only makes sense north of New Jersey, probably. And yes, you have to duct the cold air in from somewhere. But hey, that same duct could probably be used to push hot air (from the motor running) outside when it’s warm.

Why cannot these appliances be smart?

It probably costs too much.

Heat Exchange

Efficient houses that are tight and insulated need to draw in air from outside in order to maintain air quality. These houses use heat exchangers, which are fundamentally simple devices. If it’s cold outside, they pull heat from the warmed indoor air being exhausted and use it to warm up the fresh air being pulled in.

If it’s warm outside, they pull the coolness (lack of heat, technically) out of the air being sent outside to cool off (un-heat) the air being drawn in. I ain’t rocket science — fins like the ones on radiators are used to transfer heat. Fans blow one way or the other, although that’s even optional.

Am I being overly simplistic?

Costs More Than I Have

Part of the answer lies in total efficiency. Forgetting (for a moment) the materials cost of creating the additionally complex systems needed to manage this heat exchange, or the effort and energy needed to install the equipment, the question may simply be: how much energy that we’re using from electricity (or gas) to do one thing is being done for free by mother nature … and that we can get at without too much trouble. But: the costs of adding one sort or other of heat exchanger to any heating or cooling device is likely to be more than a few dollars.

How much more is irrelevant for most consumers: more cost (now) is: worse.

In a competitive world, where cash now is valued above all else (irrationally so, say the behavioral economists) … and in a world where we cannot put an accurate price on energy (such that the energy from coal has lower cost than energy from sun or wind or nuclear) … no consumer is going to pay the extra $100 to $300 it might cost for such a contraption. Even if it saves them the extra cost in a year or two.

Internal Rate of Return

This equation, known as internal rate of return, or IRR by business people, is the basis for most business investments. If there’s no risk (as in this case), an IRR that exceeds the expected cost of money over time, or interest rate, is a good investment. It wouldn’t matter whether it took 1 year or 10 years to break even, it’s still a good investment.

Yet, IRR appears to be almost completely irrelevant for regular people. Like me. In this case the calculus is usually a trade-off between a given expenditure and what I can afford now. So if I have $800 to spend, and need a new fridge and can get one that is big enough for $700, I have $100 to spend on something else. Even if the extra $100 spent would result in savings of $100/year. Normal people don’t calculate IRR. They calculate how much is left.

(It was my great epiphany, 20 or so years after graduating from college with an Economics degree, that most people don’t even begin to follow the basic assumptions that underly traditional economic theory. Back then, I spent my paycheck, and (hopefully) not a penny more. Or less. And after another 5 years, I realized the same was true with most companies. And after 25 years, I don’t think most people are that different, even if they may have the luxury of spending a little more.)

Common Sense Isn’t Common

It’s obvious to anyone with common sense that blowing hot air out of a house in winter is dumb. Are we really willing to accept “dumb” just because the economics don’t quite work out?

Answer: yes, we are willing to accept dumb until the economics work out. So: let’s make the economics work out. The sooner we do, the easier it will be.

Photo credit: striatic via Flickr


  1. […] This post was mentioned on Twitter by Tom Harrison, Spencer Kline. Spencer Kline said: RT @tomharrisonjr: Why Is My Refrigerator Running When It’s Colder Outside? […]

    Pingback by Tweets that mention Why Is My Refrigerator Running When It’s Colder Outside? | Five Percent: Conserve Energy -- — December 13, 2010 @ 1:52 am

  2. Maybe in the future, homes will be piped so that the hot and cold water lines are actually used as heat sinks for a variety of applications. Link the water heater, HVAC, refrigerator, and dryer (via heat exchangers) to the existing water lines so that waste heat from the heat pump and fridge heat water or run the dryer in the summer. In the winter, water heating and the heat pump could cool the freezer.

    In fact, this doesn’t sound impossible to me from a plumbing standpoint since it could use existing hot and cold water lines and simply add a pump and a few heat exchangers. Most of those appliances are already situated near water lines anyway!

    Comment by Daniel — December 13, 2010 @ 11:30 am

  3. Daniel —

    In my work at Energy Circle, I have been involved in understanding what it takes to avoid wasting energy in residential buildings. Techniques such as those you mention are indeed possible, and as you suggest they often need to be “built in” to the house; retrofits are even more costly.

    Thanks for your comment!


    Comment by Tom Harrison — December 13, 2010 @ 11:59 am

  4. Those are some excellent questions Tom. I guess it really comes down to ROI or does it? It seems like Americans could do so many money saving projects but the lack of education.

    To answer your question, are we really that dumb. I’ll be cynical and say most people are too busy watching Dancing with the Stars, Jersey Shore or watching YouTube to care.

    If we can make the ROI easy to understand I think more people would adopt green living. At what price of electricity and bulbs is LED light bulbs and CFL bulbs cost effect? How about a hybrid car?

    Comment by Dean — December 13, 2010 @ 11:31 pm

  5. I moved to northern Pennsylvania about 5 years ago and could not believe how long the winter dragged on here. Time and again the electricity would go out as it does in most places, so here I am without electric and without my frig working and hoping that the power will come back on so the food in my refrigerator does not spoil. O, did I happen to mention that it was about 15 degrees outside. Daaaaaaaaa. Well I decided then that would be the last time I would be in that situation. I happen to be a electrical systems designer for a defense contractor or at least I was at one time. That coming summer I designed and installed an indoor refrigerator that uses the outside cold air. The only shortcoming that it has is that I can only use it about 5 months out of the year. The items I used to build it cost about $ 20.00 dollars except for the 1 1/4th inch copper pipe. If any of the walls in your kitchen are on a outside wall then you can do the same thing. I used one of my kitchen cabinets that was on an outside wall, insulated it using 1 inch green pressed foam, drilled an 1 1/4th inch hole out the back top of the cabinet and installed a small 12 volt blower fan 1 1/2 inch in diameter, this feed a 1 1/2 inch PVC pipe on the outside of the house that then branched into 3 copper pipes 1 1/4th inch in diameter each being 5 feet long that then feed back into the bottom of the cabinet, The unit is controlled on the outside of the house by a snap disk thermometer preset at at 40 degrees N.O. about $ 3.00 dollars and also by a standard refrigerator thermometer on the inside of the cabinet about $ 8.00 dollars. The unit is powered by a 1 amp. 12 volt plug in transformer, it also has a back up battery to power it when the electricity goes out. The refrigerator uses .26 amps at 12 volts, to make that understandable to non electrical engineers it means that it will run for about a week on the same amount of electricity used to power a 60 watt light bulb for 1 hour. If anyone would like more detailed information and photos (For Free) just email me at Take care. Raymond B.

    Comment by Raymond — July 17, 2013 @ 3:19 pm

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