Saturday, March 5, 2011

The Crock Pot - Energy Efficient Dream Machine?

Crockpots are often praised for being incredibly money and energy-saving.  But is this just hype to sell crockpots?

I have been reading around and doing some analysis of my own since then, and I've decided that the hype is...well....kind of true.  It depends.  But the information out there is somewhat lacking, so I've done my own calculations.

Wondering whether crock pots are really the efficient way to cook?  Here is what I discovered:




 I wanted to know what was applicable to my own kitchen.   I know that cooking energy amounts to very little of most people's energy bill, and people get their energy from a zillion different places, so I haven't converted anything to prices.

 I just want to see how much fuel is consumed.

(Note: If you are anti-numbers, anti-math, or anti-units that make you feel like you're in Physics class, just ignore the rest of the text and check out the chart.
Note #2: If you are super pro-math, and the electricity conversions from kWh to BTU don't seem right (like off by a factor of 3), please keep reading and see why I did it that way.)      

If you want a little more of the process, feel free to continue.  I got most of my data from "Mr. Electricity," who has a pretty great site devoted to saving energy in your home.

If you're using all electric appliances, the comparisons are very straightforward:

If you're cooking a roast, a typical crock pot on low for 8 hours will use about 0.8 kWh.
The typical electric oven at 350 for 1 1/2 hours will use about 3 kWh.

I'd use the crock pot.

If you're making soup, a typical crock pot on low for 8 hours will still use about 0.8 kWh.
The typical electric stove on medium heat for 1 hour will use about 0.8 kWh.

This one looks like a toss-up

But if you're making chili that has to simmer for hours anyway, 
Same 0.8 kWh for the crock pot, but typical electric stove on medium for 4 hours will use more like 3.2 kWh.

The crock pot is the way to go for sure on this one.

But what if I cook with gas?

Then things get a little hairier.  Gas appliances are rated in therms, not watts.  So we can convert our kWhrs over to British Thermal Units or BTU to compare electric to gas.  In addition, electricity is notoriously inefficient to produce from fossil fuels in power plants (like 33% efficient).  So comparing BTU's side by side is only meaningful if we multiply our electricity BTU's by 3, to see how much actual fuel has been consumed.  I assume the gas flowing through the pipes to your appliance is 100% efficient.  Obviously, if your electric comes from solar, wind, or hydroelectric, this will not apply to you.

If I'm cooking a roast, the same average crock pot will use 2,730 BTU each hour, or about 29,000 BTU to finish the 8 hour job.  The fossil fuel usage to make this much energy back at the old power plant is more like 87,000 BTU.
In contrast, the gas oven uses about 112,000 BTU at 350 for 1 hour, or 168,000 BTU for cooking a roast for 1 1/2 hours.  Plus, if it has an electric ignition (which for almost all models, stays on for the whole cooking time...who knew?), it is drawing another 300W for 1 1/2 hours, or another 1,535 BTU (x3, to make 4605 BTU) .
This makes almost a whopping 173,000 BTU to cook a roast!

I think the slow cooker wins again!

Now, if I'm making soup: I'm still using 87,000 BTU worth of fuel back at the power plant to run my crockpot for 8 hours.
But the average gas range only uses 9,000 BTU on medium for 1 hour.  Adding in my electric ignition (300 W for an hour, x3 for inefficiency), that makes a total of 12,071 BTU for an hour.

The stove top seems to be the clear winner here.

Even my slow-simmered chili,   in the crock for 8 hours at 87,000 BTU, will simmer up on the gas range for only 48,282 BTU.  


Now, just because I have a gas stove doesn't mean I'm giving up the crock pot.  Even though it is less efficient for some applications, I still use my crock pot often, because:

  • You can leave it on while you're out of the house or while you sleep.
  • It makes even the toughest cuts of meat tender enough to fall apart on your fork.
  • Long simmering times mean fantastic flavor!
  • And my personal favorite, you can prepare dinner at 8 am when the kids are playing happily instead of at 4:30, when they've just woken up from their naps and are acting like hungry, post-hibernation bears.

I hope this long-winded comparison has been in some way helpful to you.  I really just wanted to know some facts for myself, and it got a little out of hand.  If you found this technical look at a domestic topic helpful or interesting, be sure to check out my Pressure Canning post - compete with a pressure-temperature graph! Pin It

15 comments:

  1. I'm a die-hard crock pot user - my biggest beef is that the new Crocks are made in china and they do NOT work in the same way as the "old" models used to.

    Even on Low, my new crocks heat the soup up to actual roiling and boiling - not something I feel comfortable leaving alone for long!

    Cooking times are much shorter - should I complain? well, I just find that if I want to cook a tough cut slowly for a few hours, the over hot crock is not accomplishing the same low and slow mode that I expect

    And finally, I find that the new crocks do not come with bake liners and are all oval in shape.

    My old Crock was round and had a bake liner and I was able to bake some pretty outstanding cakes in it.

    I have had several new crocks crack during cooking - in fairness, I was able to get them replaced free, but still, I don't like the threat of a pot full of soup cracking in half!

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  2. Wow, I didn't realize there were so many differences in the new Crock Pots! I had noticed they are all ovals and they seem to cook a little faster, but I didn't realize that the old ones had bake liners that are now missing. That would be pretty frightening to have a whole pot of boiling soup crack - especially if it is left alone. Wow! I have heard too that the new removable crocks are less energy-efficient. I guess every "improvement" has its drawbacks. Thank you for sharing your experiences!

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  3. I was really interested to learn that, as you found out, there are times that it is actually more energy efficient to use a regular stove top.

    I guess I had always felt that I was being very environmentally responsible by using a crock. So much for that idea!

    I'm not so sure that the newer Crocks are an improvement over the old ones - I can't bake and I can no longer get the roasting trivets for doing meat - and they overheat.

    I hope that if enough complaints are made some changes will occur. I notice on the Rival consumer complaint site there are a ton of moans about these new pots.

    I also discovered that almost no Crockpots of any type are made other than in China.

    I believe that there are two manufacturers left - one in Germany and one in Switzerland and their product costs a small fortune.

    I think it is a sad reflection on our society that we have become so consumerist that we are willing to compromise jobs and quality merchandise - if people refused to buy made in china crap, big companies would be forced to rethink their strategy.

    Well, happy crocking!

    Louise

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  4. The newer crock pots also get very hot on the OUTSIDE. I wouldn't want a kid to touch that metal on the outside, for sure. It heats up my kitchen just as much to use these newfangled crock pots as it does to use the stovetop. My kitchen is quite small, so in the summer I don't want to heat it up. In order to avoid this, I took our huge old turkey roaster (they still make them and sell for about $80) with the lift out liner and put it on a table out on the back deck, near a plug in. I've baked pies, roasted chickens, baked muffins and cakes, reheated stews and chili . . . very handy and I don't have to watch like a hawk if I keep in on a low setting. It has a knob just like ovens used to have, where you select your temperature number. My new stove is digital and something went wrong with it recently, and now I can only have the thing at 350 because it won't go higher or lower with the touchpad. Very aggravating since it's only a couple of years old.

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  5. The thing most often left out of calculations is that low temp cooking does enable the use of cheaper cuts of meat.

    So, while the crockpot may at times consume more energy its cost is a small fraction of the savings from less expensive cuts of meat. For beef dishes that can mean several dollars or more per meal. Spread the ingredient savings out over other non-beef meals and you may or may not find a net positive savings.

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    Replies
    1. Anonymous, I 100% agree. We generally use the crock pot with cheaper cuts of meat too, and it is wonderful for the job! Especially if you're trying to eat higher quality meat, every little bit you can do to save money can count! Thanks for pointing this out.

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  6. I like to use my crock pot in the summer, as I can put it out on my porch, and then I don't have to run the oven and heat up the house. The difference between using the oven and crock pot may not be substantial, but running the air conditioning, sure is costly. Our electricity rates in my area are double in the summer, over what they are in the winter.

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    Replies
    1. That's such a smart idea - cooling the house in the summer is such a energy drain. Thanks for sharing your strategy!

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  7. Best for summer is nat gas grill with baking stone on low to slow cook.

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    Replies
    1. Cool idea - I've never heard of a baking stone in a gas grill before. How do the logistics work out on that? where do you put the stone, how long/how hot do you cook, etc.?

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  8. Great idea to compare these, but I'm confused as to how to compare an electric, plug-in slow cooker with a gas hob!

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    Replies
    1. Great question. The lower half of the chart compares gas appliances (oven or stove) with electric crockpots. The energy usage can be converted into BTU (British Thermal Units), which compare electric and gas side-by-side.

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  9. I bought a Premier gas range. It has electric ignition, old fashioned knobs and no computer chips. If the power goes out during use, it will still work. The oven pilot can be lit manually if the power is out. The electronics died on my two year old stove and the cost to repair it was just too much.

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    Replies
    1. Lack of computer chips is a big bonus when the power goes out - or if you need to repair it yourself! Sounds like a good buy.

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  10. Thanks for sharing fabulous information. It' s my pleasure to read it.I have also bookmarked you for checking out new posts.solar power

    ReplyDelete

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