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I have often heard it said that it's essential to use a gas burner for cooking fried rice because you need to get the wok very hot, and only a gas burner has that kind of heat. (they're referring to those jet engine kind of burners)

enter image description here

However, I have an induction hob at home, and it has a "Power" setting, which can be used to get a pan of water boiling very quickly. The power of that setting is terrifying, but I don't know exactly how many Watts it's delivering.

I wonder if an induction hob shaped to match a wok, like this one, might actually have as much heating power as a gas burner:

enter image description here

My questions:

  1. How much actual power (in Watts) is delivered by a wok gas burner? I.E. If I added 1 litre of water to the wok, how long would it take to raise the temperature of that water by 1 degree?
  2. Does anyone know if these wok induction hobs are actually used in practice, cooking fried rice for the kinds of people who would notice if their rice wasn't fried properly?
Rocketmagnet
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    Does this answer your question? [Induction range vs gas](https://cooking.stackexchange.com/questions/5124/induction-range-vs-gas). In addition there are a ton of these questions already - use the search bar and have a browse through them to see if any suit. The answer to 1 is it depends entirely on the exact make and model of the hob and 2 is if they sell them, then people do use them... – bob1 Apr 30 '23 at 21:01
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    @bob1 Woks are a unique situation, because of the unusual (and potentially problematic for induction) shape, and because the power requirement is so far above any other cooktop situation. – Sneftel Apr 30 '23 at 22:20
  • I don't think this is a duplicate. None of the other questions specifically talked about the specialized induction wok burners. – FuzzyChef Apr 30 '23 at 22:32
  • @Sneftel I appreciate that; as I am sure you know, the major difference between gas and electric/induction is the ability of gas to significantly heat the sides of the wok beyond the contact area. I don't see that this question changes that. Induction could work for the heat requirement (I think, not being much of a physicist), but not the spread of heat, which is the major issue here and for flat bottom "woks". – bob1 May 01 '23 at 00:34
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    @bob1 - Thanks, but my question is not a duplicate of your suggested question. I'm interested in the actual amount of power delivered by the two types of hob. The other question only addresses subjective experience of using the two types of hob. – Rocketmagnet May 01 '23 at 11:23
  • Power ratings or heating applications is usually measured in British Thermal Units (BTUs), not watts. I don't know what the conversion is, but gas burners are typically rated at less than 10,000 BTUs. – Nello Lucchesi May 01 '23 at 14:56
  • Like I said in my comment - this is unanswerable as it depends entirely on the output of the hob; which will depend on the make. A professional kitchen gas wok hob in a restaurant in Hong Kong will have a different output to a home electric hob and that's about all you can say - note that even @FuzzyChef 's answer doesn't go into specifics and asks essentially "what power output do you have or can you achieve?": – bob1 May 01 '23 at 21:39
  • @bob1 - Although we can't give very specific numbers, it must be possible to give some ballpark figures. For example, if I was comparing hair dryers with kettles, I might say that hair dryers are typically in the range 1500W - 2100W. And kettles are in the range 1500W to 3000W. Our conclusion would be that hair dryers have a similar power to low end kettles, but not as high as high power kettles. Surely we can say something similar when comparing induction vs wok gas burners. – Rocketmagnet May 02 '23 at 13:12
  • @bob1 I disagree; one can totally compare heat outputs on induction and gas. I did that for a couple months when I was buying my new stove. One just has to keep in mind that energy output is only one of several factors that define the cooking experience. – FuzzyChef May 03 '23 at 17:08
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    @FuzzyChef I think we are arguing at cross purposes - of course you can compare outputs, but that wasn't the question asked, which was: *How much actual power (in Watts) is delivered by a wok gas burner?* to which the answer is "it depends on the hob". – bob1 May 03 '23 at 20:44
  • "Find the burner's BTU and apply this formula ( ( BTU / 3.41 ) * 0.4 ) for effective delivery watts" also works. – FuzzyChef May 03 '23 at 20:54

2 Answers2

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TL;DR: you can make this work, but it will require adaptation, and you need to get a high-powered burner

Despite not being Asian, I cook in my woks a lot. When I shopped for a new stove, I chose to get gas, and making wok cooking easy was one of the reasons. Several wok cooking techniques rely heavily on being able to move the wok while continuing to heat it, and only gas permits that.

However, there are folks who disagree, such as Jon Kung. In a video, he demonstrates that you can definitely make fried rice in a wok over induction. You'll notice that his technique is different, though; it's all spatula, and pretty much no shaking the wok. So clearly, it can be done, although I'll note that quality wok induction burners are quite expensive.

"How fast does water boil" is pretty much the exact wrong measure for whether a burner will work for a wok. One rarely, if ever, boils water in a wok. Instead, you need to know:

  • What's the maximum temperature that the burner supports? Wok-frying needs to go to at least 500F (260C), and many induction burners stop at 400F or 450F.
  • How quickly does the burner return the wok to temperature after ingredients cool it?

It's the latter part that makes conventional electric elements fail for woks; no matter how hot those resistance elements get, they take a long time to get there. Induction is much more promising.

As for heat equivalents: the coventional multiplier for converting electric watts to BTU is 3.41. Thus, the induction burner that Kung recommends would be about (1500 x 3.41) the equivalent of a 5000BTU gas burner, which would be pretty low. However, as you note, a lot of heat is lost by gas burners. Induction is around 90% efficient, whereas gas is as low as 40%.

So that 1500W burner would be equivalent to ( 1500 * 3.41 * (90/40) ) a 11500 BTU gas burner. Still pretty underpowered for stir-frying, though; notice that Kung gets around this by making very small batches. For comparison, I use a 25000BTU gas burner, and restaurant ones go up to 150000. So you're going to want an induction burner that's at least 2500W, which is more easily done in Europe than in the USA, where it would require special wiring in the kitchen.

FuzzyChef
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    Thanks, this is a good answer with some useful numbers to compare the power delivery. However, I must disagree about the water boil indication. The maximum possible temperature of the wok, and the time taken to return to temperature after cool ingredients go in are both affected by the power delivered to the wok by the hob. One way we can measure the actual power delivered to the wok (not just wasted as hot gas) is to time how long it takes to heat up some water. – Rocketmagnet May 01 '23 at 11:33
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    One Watt of power equals one Joule delivered per second. 4190 Joules of energy heats up one litre of water by one degree. If it takes 10 seconds to heat the water from 20 degrees to 30 degrees, then we can see that the hob is delivering 4190 Watts of power. – Rocketmagnet May 01 '23 at 11:33
  • @Rocketmagnet sure, it's one way, but it's a bad way, if what you care about is not a water-boiling vessel. The "how long does water take to boil" test was introduced by vendors of electric stoves, because those do OK at boiling water while they fail at other tasks. The "boiling water is a test of heat delivery" ignores the fact that no stove is a perfect energy-to-water system, and as such HOW the heat is delivered makes a huge difference if you're trying for specific cooking techniques. – FuzzyChef May 01 '23 at 15:41
  • If you want why it's bad in scientific terms: water has a very high thermal inertia. As such, it's a very poor way of testing how quickly heat is delivered because the difference between a rapid blast of heat vs. more gradual, but still powerful, heating is erased since the initial heat is absorbed by the water. But whether or not you have that rapid blast of heat is an essential question if you're making, say, crepes -- or fried rice. – FuzzyChef May 01 '23 at 15:45
  • If you want an analogy: consider two cars. Both have top speeds of 150mph. But car #1 has a 0-60 of 4 seconds, and car two takes 19 seconds. On a cross-country 1000mile race, the two cars are on equal footing but in a 1 mile drag race car #1 will win every time. – FuzzyChef May 01 '23 at 16:05
  • By "Thermal Inertia", I assume you mean [Specific Heat Capacity](https://en.wikipedia.org/wiki/Specific_heat_capacity). – Rocketmagnet May 01 '23 at 20:25
  • The specific heat capacity of the water is exactly what allows us to measure the power transfered to the food from the hob. The *rate* at which the water temperature increases is proportional to the power delivered by the hob, and this will let us determine the difference between, as you put it: "a rapid blast of heat vs. more gradual, but still powerful, heating" I don't mean to offend, but I honestly think you're misunderstanding power and heat capacity. – Rocketmagnet May 01 '23 at 20:32
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    I think the crucial difference between the performance boiling water and the performance frying stuff will be the temperature of the pan. The heat transfer from the gas to the pan will be proportional to the temperature difference between the gas and the pan, so will be less efficient at frying than boiling water. An induction hob would be about equal efficiency. – User65535 May 03 '23 at 13:30
  • @Rocketmagnet you came to SA looking for feedback from people who have more experience cooking in woks than you do. But once those folks share their experience, you argue with it and say it's not valid. That says to me that you don't actually want a real answer for your question; you want the answer you already believed in. – FuzzyChef May 03 '23 at 17:06
  • @User65535 did you mean "more efficient at frying"? Otherwise I don't quite understand your argument. – FuzzyChef May 03 '23 at 17:09
  • @FuzzyChef If the gases of the burner are at 800 C, the frying pan is at 400 C and the water pan is at 0 C the gases will impart roughly twice the energy into the water than they will into the frying pan, because the temperature gradient is double. The induction hob would impart about the same energy into both. – User65535 May 03 '23 at 19:41
  • Er, no? I mean, first, not a physicist but I'm pretty sure that thermal gradients are more complicated than that. Also, a natural gas flame burns at around 1900C. Also: nobody does this test using ice. – FuzzyChef May 03 '23 at 19:57
  • @FuzzyChef - I don't wish to get off on the wrong foot here. I don't doubt that you know much more about cooking than I do. But let's think about the physics here. The hob is transferring energy to the wok at a certain rate, and over a certain area of the wok. Those are the only two variables we are interested in when comparing gas and induction's ability to get a wok up to temperature. In a both hobs, the maximum temperature that can be reached by the wok is the equilibrum temperature when the heat energy leaving the wok by radiation and convection equals the energy entering the wok. – Rocketmagnet May 07 '23 at 22:06
  • @FuzzyChef - Assuming for the sake of similicity that the area of energy entering the wok from both types of hob is roughly similar, then the only variable we're interesting in is the rate at which energy is being transferred from the hob to the wok. This will determine the equilibrium temperature of the wok, and the rate at which it can be heated (including how quickly it recoveres after cold food is put in it). The energy rate is called power, and is measured in Watts. – Rocketmagnet May 07 '23 at 22:09
  • @FuzzyChef - Whatever a wok is normally used for, we can measure the power transferred from the hob to the food be measuring the rate at which something in the wok heats up. It's very convenient to use water for this, because we know its specific heat capacity, and it makes good contact with the surface of the wok. You could use an oil instead. This simply allows us to compare the difference between types of hob with regard to the power transferred (which in my opinion is the main variable relevant when people talk about induction hobs not being powerful enough). – Rocketmagnet May 07 '23 at 22:14
  • @FuzzyChef - If you know of another variable that's relevant to the question of induction hobs being powerful enough compared to a good gas burner, and a way to measure that variable, then I'm genuinely interested to know. – Rocketmagnet May 07 '23 at 22:14
  • Why not measure the temperature of the surface of the wok? That's what you care about, after all. You'd want to know it both over time (at, like 10s intervals), and over a map of the surface (gas will be more spread out). – FuzzyChef May 08 '23 at 16:45
  • Anyway, this sounds like it should be its own separate question (regarding the best/worst way to measure real stove output). – FuzzyChef May 08 '23 at 16:47
  • @FuzzyChef - No, I'm less interested in the temperature of the surface of the wok, and more interested in the *power* delivered by the hob to the wok, as was described in my question. – Rocketmagnet May 09 '23 at 15:44
  • So, you want that information, even though it's irrelevant to actually cooking in the wok? I can't help you then. – FuzzyChef May 09 '23 at 16:12
  • Completely by chance, I came across this video by J. Kenji López-Alt, talking about different types of wok burners. In that video, he mentions the technique of judging the power of a burner by timing how long it takes to boil water. https://www.youtube.com/watch?v=cpoSvprBJpE – Rocketmagnet May 27 '23 at 15:59
  • You may have noticed that you're not getting any other answers to this question. That isn't a coincidence. – FuzzyChef May 27 '23 at 19:54
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I had a chance recently to measure the power delivered by a reasonably high power gas burner. A professional Taiwanese chef was using it to cook egg fried rice, which everyone agreed tasted delicious, so I am going to assume it was of sufficient power.

I placed 500g of water in the wok and let the temperature equilibrate for a few seconds, then measured the temperature. Then I put the gas burner on full blast for 10 seconds, then switched it off and let the water equilibrate again for a few seconds.

The initial water temperature was 22.8ºC. After heating, the water was 44.3ºC; a rise of 21.5ºC.

The specific heat capacity of water is 4184 J/(kg K), meaning that approx 45 kJ of energy had been delivered to the water, over 10 seconds. Or 4.5kW of power over that period.

Most consumer induction hobs only seem to go as high as 3kW (presumably measured on the wire, and not as actual power delivered to the wok) so probably aren't delivering as much power as this gas burner.

However, some commercial induction hobs designed for woks, like the Target Catering Equipment range can go as high as 5kW. However, it's not clear if that's the maximum power consumed by all the rings together, or the maximum power that a single ring is capable of.

In conclusion, consumer induction hobs aren't far off the power, but don't get as high as needed, but some companies may produce hobs with enough power.

Rocketmagnet
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