[EvaH (OP)]

Bobby wants to know:

Induction stoves are described as being more efficient than traditional electric stoves. When boiling, for instance, a pot of water, it takes the same amount of energy to heat the water to a boil no matter what the heat source is. My question: how is heating the pot through induction more efficient than heating the stove underneath? The stove heating element is designed to produce heat, but the pot isn't.

What do you think?

[syhprum]

The element in the stove is not designed to produce heat only the oscillating magnetic field that produces heat in the pot placed above it any heating of the stove element is only due to conduction from the pot.
The gain in efficiency is due to no energy being wasted heating the stove element.

[Petrochemicals]

Bobby wants to know:

Induction stoves are described as being more efficient than traditional electric stoves. When boiling, for instance, a pot of water, it takes the same amount of energy to heat the water to a boil no matter what the heat source is. My question: how is heating the pot through induction more efficient than heating the stove underneath? The stove heating element is designed to produce heat, but the pot isn't.

What do you think?

Being electric, they are undoubtedly more efficient than gas at the burner face,  but it depends on where you get your electric frome,  probably carbon via steam down aluminium.

[bbissett]

The element in the stove is not designed to produce heat only the oscillating magnetic field that produces heat in the pot placed above it any heating of the stove element is only due to conduction from the pot.
The gain in efficiency is due to no energy being wasted heating the stove element.

Hi, I should maybe have been more clear. I know there's not a heating element in an induction stove. Am wondering how it's more efficient to cause the pan to produce heat compared to a traditional electric stove with a heating element designed for that purpose.

Thank you

[Bored chemist]

with a heating element designed for that purpose.

It's difficult to design an electric heater which doesn't have an efficiency of practically 100%.

However, with a heating element on the hob of a cooker, some energy is lost to heating the air without doing anything useful- like heating the pan. And, in order to heat the pan quickly, the hob has to get very hot- often red hot. That means it's losing heat in all directions, and only some is going into the pan.
With an induction hob, the heat is generated in the pan, so there's less loss.

[Colin2B]

I know there's not a heating element in an induction stove. Am wondering how it's more efficient to cause the pan to produce heat compared to a traditional electric stove with a heating element designed for that purpose.

As @syhprum says, it takes energy to heat the element before it can heat the pan whereas the inductor heats the pan directly. There is some heat lost to the stovetop, but not as much as in the element.

EDIT: crossover with @Bored chemist

[alancalverd]

An ohmic heater immersed in water (an electric kettle) is clearly the most efficient means of boiling water, particularly if the kettle is an insulator, but an induction cooker is the most efficient device for any form of cooking that begins with shallow frying.

[hamdani yusuf]

There are some models of electric kettle where the heating element is located inside and fully submerged by the water. This could be more efficient than induction stove which usually need a cooling system for their high frequency generator electronics.

[vhfpmr]

Wikipedia are quoting the US DoE efficiency tests as an average of 72.2% for induction hobs, and 71.2% for resistive ones.

https://en.wikipedia.org/wiki/Induction_cooking

[hamdani yusuf]

Wikipedia are quoting the US DoE efficiency tests as an average of 72.2% for induction hobs, and 71.2% for resistive ones.

https://en.wikipedia.org/wiki/Induction_cooking

I think the number refers to resistive heater where the heating element is located below the pot.

[vhfpmr]

Wikipedia are quoting the US DoE efficiency tests as an average of 72.2% for induction hobs, and 71.2% for resistive ones.

https://en.wikipedia.org/wiki/Induction_cooking

I think the number refers to resistive heater where the heating element is located below the pot.

The figure for resistive elements refers to resistive elements, and the figure for induction hobs refers to induction hobs.

[hamdani yusuf]

Wikipedia are quoting the US DoE efficiency tests as an average of 72.2% for induction hobs, and 71.2% for resistive ones.

https://en.wikipedia.org/wiki/Induction_cooking

I think the number refers to resistive heater where the heating element is located below the pot.

The figure for resistive elements refers to resistive elements, and the figure for induction hobs refers to induction hobs.

The article describes the method. It uses aluminum block as the heat load and compares heat content in the block with energy consumed by the heat element.
In case of fully submerged resistive heater, almost all of the energy is transfered to heated media.

[alancalverd]

Problem is that an induction cooker won't heat an aluminum block directly. You have to use a ferromagnetic intermediate layer, which reduces the efficiency of energy transfer to the aluminum. One might have hoped the DoE would use a steel block for both tests.   

[vhfpmr]

In case of fully submerged resistive heater, almost all of the energy is transfered to heated media.

The thread is about hobs, not kettles

Problem is that an induction cooker won't heat an aluminum block directly.

That's why they're using stainless steel.

[hamdani yusuf]

The thread is about hobs, not kettles

Here is the original question.

Induction stoves are described as being more efficient than traditional electric stoves. When boiling, for instance, a pot of water, it takes the same amount of energy to heat the water to a boil no matter what the heat source is. My question: how is heating the pot through induction more efficient than heating the stove underneath? The stove heating element is designed to produce heat, but the pot isn't.

case A : heating the pot through induction
case B : heating the pot through heat conduction
The efficiency is defined by portion of electrical energy input which is transfered to the heated media. The confusion came from the examples given, which one is counted as the heated media. Is it the water? Is it the pot?

Is it acceptable or even preferred to heat the water without having to heat the pot? This is possible using various methods, such as microwave, electrode boiler, and immersed resistive heater. In this cases, the pot can be made of heat insulating materials.