Copper vs Aluminum - CenturyLife Boiling Speed Test

Hi seitan,

I have two Vollrath Induction units, the Cadet and Pro, both 1800 watts. I have to run my Pro at 50% for them both to heat water in a pot about the same.

Ray

This is a bit of a fudge. There can’t be much heat being scavenged by the Flare on electric. Should work really well on gas, though.

The Turbo bottom idea is a legitimate energy saver, at least in institutional use where a lot of boiling and simmering is done.

Aloha,
Kaleo

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Here is a study from, I kid you not, “Pablo the Tree Hugger”:

His home brew findings are in line with other studies I’ve seen, which place the electric kettle at around 80-90% efficient, electric induction and coils at 70-80%, the microwave oven at 60-70% efficient, and the gas hob at 30-35% efficient.

Here is another study which shows induction is more efficient than coils for only smaller amounts of water, however, as the amount of water to be boiled increases the regular coil catches up and then surpasses induction:

https://www.centurylife.org/is-induction-more-efficient-than-electric-coil-or-gas-an-energy-efficiency-comparison-between-stoves/

Study Title: "Is Induction More Efficient Than Electric Coil or Gas? An Energy Efficiency Comparison Between Stoves

DEBUNKING THE MYTH THAT INDUCTION IS MORE EFFICIENT THAN ELECTRIC COIL"

It looks like both the induction and the coil are similar to the electric kettle in terms of efficiency, but the kettle wins out because it is a closed insulated system in direct contact with the water and no additional vessel to heat. Again as noted by @kaleokahu above, for stove top applications generally the thinner the vessel, the faster the boil.

Finally, while electric or induction may be more efficient in the kitchen, this does not mean that they are most efficient overall system for the environment due to power losses in transmission over distances. With natural gas there is essentially no power loss in transmission.

Absolutely. Considering my house and the environment, gas and wood are probably the most efficient, and their terrible heat-to-food transfer efficiency is actually a help in keeping my home heating costs down.

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I think the problem is also these pots cost more… so something it is “on average, do I really save money?”

Absolutely agree. The heating element is directly or very closely to the water. The heat transfer is very efficient.

Right. That is different concern too about comparison gas vs induction. One use gas, and the other uses electricity. Beside the power loss over transmission, there is also consideration for the energy generation. It is probably much easier generate/find gas than to generate electricity. Electricity is not a raw (primal) energy. So you may need to burn coal to get electricity? So what about that energy loss?

[quote=“VikingKaj, post:25, topic:7835”]
From the studies I’ve seen, the most efficient home system for heating water is an electric kettle.

Finally, while electric or induction may be more efficient in the kitchen, this does not mean that they are most efficient overall system for the environment due to power losses in transmission over distances. With natural gas there is essentially no power loss in transmission. [/quote]
I can also agree, as the Bodum electric kettle I used to have was faster even than the Turbo Pot kettle I’m using now. (If you’re a thermal carafe user dead-set on pre-heating the carafe with hot water, using an electric kettle wastes far less time, energy, and water than letting the hot water tap run! I used to pre-heat, but my thermometer testing showed it provided little benefit to keeping my coffee hotter longer.)

My decision to replace with a gas-powered kettle over another electric was mostly driven by the occasional power outages I now experience at my new location. When the power fails, I can still boil water for coffee. :slight_smile:

Hi VikingKaj,

Let’s go one step at a time. In one’s kitchen, hobs that use induction for typical tasks that bring liquids to a boil are faster–much faster–than hobs that use electrical coils or gas. If you make a transition from either traditional type of stove to induction, the difference is obvious and impressive–almost amazing.

More importantly, induction hobs give much better control over the temperature of the pot during cooking.

Pablo never considers induction, and the electric kettle he recommends works like induction. Your conflating of induction with coils in your comment mixes very different types of heating.

Franz tests a hypothetical theory of efficiency by carrying out a a boiling water task that would rarely, if ever, be a cooking task. Knowing the induction unit would be much faster, Franz runs it at 50%, arguing that it equates for energy consumed between it and the cheapie electric coil. He heats up more than 1/2 gallon of water, way more than the amount one usually heats up for steaming or pressure cooking. He uses a thick bottom base pot, which reduces the induction effect–especially at 1/2 power. Under those conditions, the induction speed advantage disappears.

So, if one slowly heats up a large volume of liquid in a pot with a thick base, induction doesn’t save any money over a cheapie coil. OK.

Now, if it’s only a small amount of liquid, heated at full power on a pot with a thin base . . .

We know the induction speed to boil will be much faster than coil. As time goes down, cost goes down. Maybe an efficiency comparison under those conditions might give one a different outcome?

Maybe Franz hasn’t debunked anything.

Ray

Hi Eiron,

Thanks for the link. They may be designed for both gas and electric, but their own blurb specifies that the speed performance is noted for gas stoves:

“in fact, in tests performed by Oxford University, Flare Cookware was shown to cook up to 40% quicker on gas stoves than a conventional pan.”

For gas, the design makes some engineering sense. I doubt the fins are doing anything on an electric coil burner.

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Hi Ray,

“I have two Vollrath Induction units, the Cadet and Pro, both 1800 watts. I have to run my Pro at 50% for them both to heat water in a pot about the same.”

Interesting. Maybe some induction units are more efficient than others? Maybe more amps in the Mirage Pro? What do you think accounts for the difference?

Hi Seitan,

Intelligence. The difference between the Pro and Cadet is almost entirely software. That’s why it costs twice as much. And, of course, the smartest of them all (so far) is the Control Freak (and by far the most expensive).

Even at 1800 Watts, my Vollrath is overpowered.

Ray

Not in the slightest.

Thanks for the feedback folks. I don’t have much spare time these days, but here are some thoughts:

  • I did not test everything on flame–for consistency and to avoid problems of using undersized pots. I would prefer testing on induction but copper is incompatible, so coil it was. I tested on electric coil and swapped the pot positions and averaged in case the coils delivered slightly different wattages or wobbles or whatever.

  • However, I did test a copper pot vs. copper-disc base pot (5 quarts each, 4 quarts of water) on a friend’s gas range a while back, and the all-copper pot did not boil faster–even when I cranked up the flame. So I wouldn’t bank on “side heating” to necessarily make clad beat non-clad. And some materials are more conductive than others. Anodized (black-appearance) aluminum would be better than shiny stainless at absorbing hot gas heat, for example. To get a bigger effect on gas, you would want something like the Turbo Pot mentioned above.

  • My results may be counterintuitive except when you consider that the water is drawing heat away from the copper or aluminum disc bottom. So even though copper is more efficient at letting heat pass through, aluminum is pretty good too, and apparently the water-convection current effect is such that it dwarfs the effect of the disc material. See ChemK’s point about glass pots not taking forever to boil despite glass being a far worse conductor of heat.

  • Yes, thickness matters, as Kaleo said. You are losing a bit of energy in heating the metal at the bottom and/or sides which is radiated away. An ultrathin pot would boil faster than anything else. But nobody would buy it. Would you buy a pot made out of paper-thin aluminum foil? Exactly.

  • Some people seem to be wondering if increasing water quantity will seriously change things. The amount of water doesn’t seem to materially change things up to 4 quarts. Even if going up to, say, 6 quarts of water would result in a minor victory for [insert construction of your choice], would that tiny amount of time/energy saved justify a large increase in cost? E.g., would you spend an extra $300 to save two dollars per year? Ignoring inflation and opportunity costs, that’s a 150 year payback period.

  • I believe in quantitative methods when possible. This means accurate, objective measurements. Accurate testing is trickier than it might seem. E.g., I wound up weighing water for far greater accuracy. Equalizing temperatures also took a long time (I let water sit overnight). Etc. These might seem minor but they can impact testing. I’m not even going to get into matters of pressure, humidity, equipment sensitivity and calibration, etc.

Finally, I don’t think any of these things changes the larger point that I made in my writeup: it doesn’t make much sense to spend $$$$$ on a pot used for boiling water when a much cheaper pot performs nearly identically. If you do something other than boiling water then there is more room for argument.

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Franz,

The issue is not rigor. It’s measurement error–and criterion.

There is only one way to establish the reliability of a dependent measure (criterion): one has to measure it. A test-retest correlation gives one a good estimate of the error in your measurement. This can be used to generate error bars.

Temperature may not be as good a criterion as you think it is.

Ray

Nice summary.

Then do your own test, Ray.

I think I see the similarity. An induction hob generates heat via the body of the steel pan which in direct contact with the water it boils. The kettle element heats up and is also directly in contact with the water.

Lots of other differences but direct contact between heating elements is similar.

I’m sure you believe that your “criterion” of stopping when one sees “a certain rolling boil pattern in the water of the pan” is better than simply measuring the temperature. Thanks for the advice, but I’ll stick with my calibrated thermometer and multiple rounds of testing.

Also, I forgot to respond to Seitan in my bullet point list but yes, I’d say that pot material matters little for boiling (within reason; I’m not comparing glass pots or anything). So clad, aluminum, copper, etc. aren’t going to differ much in boiling speed all else equal. Perhaps there would be more of a difference at, say, 30 quarts or something, but I don’t consider that typical residential use.

Franz,

Your missing my point. Any criterion must be established prior to collecting data in a scientific study.

Without any validation, or experimentation, it is obvious that small amounts of water come to a boil at about the same time in most any pan with most any criterion. I did it subjectively with “rolling boil.” That’s common sense–and that’s what you concluded as well.

Now, if you want to do a scientific study, you need to do it the right way, which is to validate your criterion. Your criterion of temperature was not tested for reliability, error bars were not given for your measures, nor was the variable shown to be perfectly continuous with energy changes over the temperature interval you chose to measure.

Either stick with common sense–or do your study correctly.

Ray

I thought his test criteria were clearly established: time to reach 200°F from room temperature water.

He then repeated the experiment 3 times with each pan and averaged the data to reduce errors. He understood that there were uncontrolled variables (pressure, humidity, thermometer accuracy) - but the repetition would tend to average the impact of those as they affect each pan the same way on each day.

OK iff we had the raw data we could check to see if the differences between pans were similar on each experimental run and thus see how statistically reliable the method was. But its only a bit of fun so what is the point…?