A little OT: electric kettle versus kettle on induction ring

[Paul]

My solar installation is limited to 5kW. It can go to 7 for a bit, but I try
to avoid it. Trouble is, our kettle uses almost 3kW. So if the water heater
is on and the aircon etc. at the same time, we can have problems.

I noticed that our new induction hob has a "boost" facility which makes a
pan of water boil very quickly. I'm pretty sure it consumes at a lower rate
than the kettle. Is this possible? I would have thought a kettle with
submerged element would be nigh on 100% efficient.

Opinions?

--

Paul.
https://paulc.es

[spuorg...@gowanhill.com]

On Thursday, 16 June 2016 17:32:14 UTC+1, Paul wrote:
> I noticed that our new induction hob has a "boost" facility which makes a
> pan of water boil very quickly. I'm pretty sure it consumes at a lower rate
> than the kettle. Is this possible? I would have thought a kettle with
> submerged element would be nigh on 100% efficient.

A kettle with a submerged element is nigh on 100% efficient.

You will have to check the hob instructions for details of its consumption at various powers.

If you want to reduce instantaneous load, get a smaller and lower-wattage kettle for occasional cuppas.

Owain

[Andy Burns]

Chris Hogg wrote:

> Paul wrote:
>
>> My solar installation is limited to 5kW.
>

> That reads as if solar is your only source of electricity. Surely not,
> or are you out in the sticks with no mains supply?

Spain IIRC.

[Tim Watts]

The kettle is more efficient as you say - the only 2 losses from that
system are:

1) Heating of the supply cables;

2) Some loss to the air through the wall of the kettle.

Otherwise, it's practically a perfect system.


However, the induction cooker on metal boost will do the job extremely
quickly. But I suspect there will be some losses from the electronics as
heat and could even be some small losses as eddy currents in more remote
metalwork.

[Robin]

ISTM both are 100% efficient at converting energy from electrical to
heat. The problem is how much of that energy goes "usefully" to raise
the water to boiling and how much is "wasted" by way of heating the
kettle itself, the hob, the worktop, and the room generally by way of
evaporation, convection, conduction, radiation and noise. So I'd think
a first order test would be to put the same amount of water in each
kettle and let them come to equilibrium at the same temperature. Then
time how long each takes to boil the water. Multiply those times by the
power of each (as a first approximation the rated power) to give a
relative[1] measure of efficiency with the lower figure the better.

<envy_mode? Or - since you are living with solar power - forget
efficiency of boiling water and open a bottle of something cool :)

[The same mass of water is raised by the same temperature using the same
energy.

If the hob's power is P1 kW and the kettle's P2 and they take times T1
and T2 respectively to boil the water then the *total* energy each used
- including waste - is P1 x T1 and P2 x T2. SO the more efficient is
the one with the lower PxT figure.]




--
Robin
reply-to address is (intended to be) valid

[ARW]

"Paul" <wibble...@gmail.com> wrote in message
news:dsg2kc...@mid.individual.net...

> My solar installation is limited to 5kW. It can go to 7 for a bit, but I
> try
> to avoid it. Trouble is, our kettle uses almost 3kW. So if the water
> heater
> is on and the aircon etc. at the same time, we can have problems.

Then do not use them all at the same time.

How do you make a brew at night?

What happens if you cook a dinner?




--
Adam

[Rod Speed]

Paul <wibble...@gmail.com> wrote

> My solar installation is limited to 5kW. It can go to 7 for a bit, but I
> try
> to avoid it. Trouble is, our kettle uses almost 3kW. So if the water
> heater
> is on and the aircon etc. at the same time, we can have problems.

What you need is some way to turn the
water heater off when running the kettle.

> I noticed that our new induction hob has a "boost"
> facility which makes a pan of water boil very quickly.
> I'm pretty sure it consumes at a lower rate than the kettle.

No it doesn't if it boils the same quantity of water quicker.

> Is this possible?

Nope.

> I would have thought a kettle with submerged
> element would be nigh on 100% efficient.

Correct.

> Opinions?

Facts are better.

[Brian Gaff]

Well, kettles elements are insulated, so that insulation has tobe heat
conducting. The surface area of the element cannot be as great as the bottom
of a pan, and you have thermal churning in both systems to be able to get
the water uniformly hot. As you say though, induction through a gap should
one would imagine be far lessefficient overall.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
bri...@blueyonder.co.uk
Blind user, so no pictures please!

"Paul" <wibble...@gmail.com> wrote in message
news:dsg2kc...@mid.individual.net...

[harry]

On Thursday, 16 June 2016 17:32:14 UTC+1, Paul wrote:

The way to go is to get a jug instead of a kettle.
They are lift off (the base) too.
You can boil the precise amount of water you need (They have a measuring scal, often takes only seconds.
Boils very small quantities if that's all needed.
Usually they have a smaller (in Kw) heating element than a kettle.

[polygonum]

You make it sound as if the "boost" comes from magic!

All that happens, so far as I am aware, is that some induction rings
allow themselves to be over-run for a few minutes.

A ring rated at, say, 1.8 kW, would run at 2.7 kW for five minutes. Or
something like that. At the end of the over-run it will revert to
standard rating. So using boost wouldn't help you significantly reduce
your maximum loading.

On a typical four ring hob, you'll probably find that only two rings at
a time can be on boost.

I really doubt a kettle can be beaten for efficiency.

--
Rod

[Paul]

harry wrote:

> On Thursday, 16 June 2016 17:32:14 UTC+1, Paul wrote:
>> My solar installation is limited to 5kW. It can go to 7 for a bit, but I
>> try to avoid it. Trouble is, our kettle uses almost 3kW. So if the water
>> heater is on and the aircon etc. at the same time, we can have problems.
>>
>> I noticed that our new induction hob has a "boost" facility which makes a
>> pan of water boil very quickly. I'm pretty sure it consumes at a lower
>> rate than the kettle. Is this possible? I would have thought a kettle
>> with submerged element would be nigh on 100% efficient.
>>
>> Opinions?
>
> The way to go is to get a jug instead of a kettle.

I thought all modern electric kettles were "jugs".

--

Paul.
https://paulc.es

[Paul]

ARW wrote:

> "Paul" <wibble...@gmail.com> wrote in message
> news:dsg2kc...@mid.individual.net...
>> My solar installation is limited to 5kW. It can go to 7 for a bit, but I
>> try
>> to avoid it. Trouble is, our kettle uses almost 3kW. So if the water
>> heater
>> is on and the aircon etc. at the same time, we can have problems.
>
>
>
> Then do not use them all at the same time.

I already have the water heater on a timer so it's only on during sunlight
hours, but on a hot summer day, we may have the aircon on at midday and
fancy a cup of tea.

> How do you make a brew at night?

Put the kettle on.

> What happens if you cook a dinner?

Well, yes, every evening the usage peaks at around 5kW. We avoid making tea
while dinner is cooking.

--

Paul.
https://paulc.es

[Paul]

Chris Hogg wrote:

> On Thu, 16 Jun 2016 18:32:11 +0200, Paul <wibble...@gmail.com>
> wrote:
>
>>My solar installation is limited to 5kW. It can go to 7 for a bit, but I
>>try to avoid it. Trouble is, our kettle uses almost 3kW. So if the water
>>heater is on and the aircon etc. at the same time, we can have problems.
>

> That reads as if solar is your only source of electricity. Surely not,
> or are you out in the sticks with no mains supply?

We have gone off grid. In Spain they decided to tax sunlight, so we threw
the fuse.

> Induction hobs have an efficiency of around 72%*, but a kettle should
> be pretty close to 100% as you say, so if your hob boils water faster
> than the kettle boils the same quantity of water, then your assumption
> that the hob uses less power must be incorrect.

I'll have a look later for interest's sake, but it sounds so far like my
basic hunch was right ie; the kettle will be more efficient.

--

Paul.
https://paulc.es

[charles]

In article <797f36ac-6f73-4c26...@googlegroups.com>, harry

They are kettles = jug kettles

--
from KT24 in Surrey, England

[whisky-dave]

On Thursday, 16 June 2016 17:32:14 UTC+1, Paul wrote:

I donl;t understand how a kettle can be clos eto 100% efficient.
My kettle is just over 3KW after I;'ve boiled it I can burn my hand on it;s plastic case even the handle gets warm.
I aslo see steam coming out of teh lip.
I assume this heat is effectively wasted as it doesn;lt end up in my cup of tea.

So other than my physics teacher explaining on the latent heat of evapouration of water and how using a calorimeter or a dewer flask can anyone explan to me how a standard kettle can be anywhere near 100% efficient ?

[whisky-dave]

On Thursday, 16 June 2016 20:25:52 UTC+1, Tim Watts wrote:
> On 16/06/16 17:32, Paul wrote:
> > My solar installation is limited to 5kW. It can go to 7 for a bit, but I try
> > to avoid it. Trouble is, our kettle uses almost 3kW. So if the water heater
> > is on and the aircon etc. at the same time, we can have problems.
> >
> > I noticed that our new induction hob has a "boost" facility which makes a
> > pan of water boil very quickly. I'm pretty sure it consumes at a lower rate
> > than the kettle. Is this possible? I would have thought a kettle with
> > submerged element would be nigh on 100% efficient.
> >
> > Opinions?
> >
>
> The kettle is more efficient as you say - the only 2 losses from that
> system are:
>
> 1) Heating of the supply cables;
>
> 2) Some loss to the air through the wall of the kettle.

so the walls of the kettle don;t get hot. news to me.
Steam never comes out of teh kettle.

yuo know why steam is an efficint clearer don;t you.
It''s the energy it holds and when it comes out of the spout of your kettle it's lost.

[whisky-dave]

I have a jug gettle which is 3kw.

can anyone explain why the case of rthe kettle gets hot and reamins hot
for a while after the water is gone.
And where does the ENERGY comes from to heat the kettle (rather than the water)
and where the ENERGY comes from to create the steam that comes out of my kettle ?

[dennis@home]

Different kettle designs may have different efficiency.
The obvious one is to make them tall and narrow so you can heat less
water and to have a flat element in the base rather than the rings in
old style kettles. And you can insulate them to make them safe to touch
as well as potentially saving energy.

And alternative is a one cup dispenser of which there are two types..
one that puts out a flow of near boiling water that is suitable for
coffee but not real tea and the other that puts out a whole cup of
boiling water that is OK for tea but maybe a bit hot for coffee.

They are probably both more energy efficient than a kettle if they
dispense the correct quantity.

[The Natural Philosopher]

On 17/06/16 12:03, Chris Hogg wrote:

> The argument is that almost all of the electrical energy dissipated in
> the heater element gets transferred to the water. OK, so a small
> amount of heat escapes through the sides of the kettle and is lost,
> and a small amount of heat escapes via steam from the spout when the
> kettle starts to boil and before the thermostat cuts off the supply.
> But both of these heat losses are small compared to the amount of heat
> used in heating the water from say 20C to 100C, especially if the
> kettle is insulated and the thermostat quick to respond. No one is
> claiming exactly 100% efficiency, but it must be well over 90% I
> should think.
>
> Ironically, when comparing the energy compared to boil water on a gas
> hob versus an electric kettle, the gas hob probably comes out on top,
> because of the energy losses in generating the electricity, and
> transmission losses getting it to your house.
>
Well that implies that the gas hob is better than 40% efficient, which I
doubt...


--
All political activity makes complete sense once the proposition that
all government is basically a self-legalising protection racket, is
fully understood.

[Paul]

Chris Hogg wrote:

> Ironically, when comparing the energy compared to boil water on a gas
> hob versus an electric kettle, the gas hob probably comes out on top,
> because of the energy losses in generating the electricity, and
> transmission losses getting it to your house.
>

I have a gas cooker in my garage (just in case). Haven't had to use it yet.
We get a lot of sunshine here. Paid out for a generator as well (just in
case), but haven't needed it yet in 6 months or so.

I think my inverter is quite efficient and the leccy only has to travel from
the roof to the inverter. Oh, and it's free :-)

--

Paul.
https://paulc.es

[dennis@home]

It implies the gas kettle is good at capturing the heat as the hob is
just burning 100% of the gas.

[dennis@home]

On 17/06/2016 11:51, whisky-dave wrote:


> I have a jug gettle which is 3kw.
>
> can anyone explain why the case of rthe kettle gets hot and reamins hot
> for a while after the water is gone.

OK but you have to supply some information..

what's it made from
what's the wall thickness
what's the dimensions
what is the surface texture
are there any draughts
how much water do you boil
how much is left
how long between boils

> And where does the ENERGY comes from to heat the kettle (rather than the water)
> and where the ENERGY comes from to create the steam that comes out of my kettle ?
>

That's the easy one.. the sun and a supernova.

[dennis@home]

On 17/06/2016 18:51, Chris Hogg wrote:

> Not exactly a lab comparison, but this guy reckons the total energy
> efficiencies of boiling water on a gas hob or in an electric kettle
> are about the same. But as with so many things these days, the result
> you get depends on the initial assumptions you make, in this case on
> the efficiency of the generating and transmission process.
> http://tinyurl.com/jgm7ynb
>

Thats not even a kettle designed for gas, most of the heat would just go
up the sides.

This is a kettle designed for gas, you may notice the heat exchanger
lets the flame in to capture more of the heat.

https://www.amazon.co.uk/Simplex-Heritage-Gas-Kettle-Chrome/dp/B0006GMMCM

[Dave Plowman (News)]

In article <3ud8mbdu7ut16apru...@4ax.com>,

Chris Hogg <m...@privacy.net> wrote:
> Not exactly a lab comparison, but this guy reckons the total energy
> efficiencies of boiling water on a gas hob or in an electric kettle
> are about the same. But as with so many things these days, the result
> you get depends on the initial assumptions you make, in this case on
> the efficiency of the generating and transmission process.

I'd be surprised. In a small kitchen, boiling anything on a gas hob tends
to increase the temperature in the room. Not sure I've ever noticed that
with an electric kettle.

--
*Eschew obfuscation *

Dave Plowman da...@davenoise.co.uk London SW
To e-mail, change noise into sound.

[Dave Plowman (News)]

In article <hnjamb15t978js5s7...@4ax.com>,
Chris Hogg <m...@privacy.net> wrote:

> On Sat, 18 Jun 2016 11:36:54 +0100, "Dave Plowman (News)"
> <da...@davenoise.co.uk> wrote:

> >In article <3ud8mbdu7ut16apru...@4ax.com>,
> > Chris Hogg <m...@privacy.net> wrote:
> >> Not exactly a lab comparison, but this guy reckons the total energy
> >> efficiencies of boiling water on a gas hob or in an electric kettle
> >> are about the same. But as with so many things these days, the result
> >> you get depends on the initial assumptions you make, in this case on
> >> the efficiency of the generating and transmission process.
> >
> >I'd be surprised. In a small kitchen, boiling anything on a gas hob
> >tends to increase the temperature in the room. Not sure I've ever
> >noticed that with an electric kettle.

> You might if the 60-65% inefficiency of a power station was directed
> into your kitchen (in proportion to the power you were using, of
> course).

Working out the true efficiency of any domestic power source accurately is
impossible. Far too many variables. Even within the same day.

--
*I want it all and I want it delivered

[Dave Plowman (News)]

In article <1qjambt6hm5pv6rs1...@4ax.com>,

Chris Hogg <m...@privacy.net> wrote:
> >Thats not even a kettle designed for gas, most of the heat would just
> >go up the sides.

> Which is probably why the guy found that a small flame was more
> efficient than a larger one. Less of the heat lost up the sides, more
> absorbed by the water.

But the longer it takes to reach boiling point, the greater any heat
losses become as a percentage.

--
*Vegetarians taste great*

[Dave Plowman (News)]

In article <n4lamb91spnakit6p...@4ax.com>,
Chris Hogg <m...@privacy.net> wrote:
> Well, quite, but you can make a reasonable estimate. Hence my 60-65%.
> We're not looking for three-decimal-place accuracy! My point still
> stands. The heat from a gas ring that doesn't go into the water goes
> into the kitchen. The heat from a power station furnace that doesn't
> go into generating electricity goes up the chimney.

That assumes all power generation is by gas. Or, indeed, heat.
Then there's how much energy is needed to get the gas out of the ground,
transport it, etc.

--
*I don't suffer from insanity, I enjoy every minute of it *

[charles]

In article <180620161646248544%timst...@greenbee.net>, Tim Streater
<timst...@greenbee.net> wrote:
> In article <n4lamb91spnakit6p...@4ax.com>, Chris Hogg
> <m...@privacy.net> wrote:

> >On Sat, 18 Jun 2016 14:48:56 +0100, "Dave Plowman (News)"

> ><da...@davenoise.co.uk> wrote:
> >
> >>In article <hnjamb15t978js5s7...@4ax.com>, Chris Hogg
> >> <m...@privacy.net> wrote:
> >>> On Sat, 18 Jun 2016 11:36:54 +0100, "Dave Plowman (News)"
> >>> <da...@davenoise.co.uk> wrote:
> >>
> >>> >In article <3ud8mbdu7ut16apru...@4ax.com>, Chris Hogg
> >>> > <m...@privacy.net> wrote:
> >>> >> Not exactly a lab comparison, but this guy reckons the total
> >>> >> energy efficiencies of boiling water on a gas hob or in an
> >>> >> electric kettle are about the same. But as with so many things
> >>> >> these days, the result you get depends on the initial assumptions
> >>> >> you make, in this case on the efficiency of the generating and
> >>> >> transmission process.
> >>> >
> >>> >I'd be surprised. In a small kitchen, boiling anything on a gas hob
> >>> >tends to increase the temperature in the room. Not sure I've ever
> >>> >noticed that with an electric kettle.
> >>
> >>> You might if the 60-65% inefficiency of a power station was directed
> >>> into your kitchen (in proportion to the power you were using, of
> >>> course).
> >>
> >>Working out the true efficiency of any domestic power source accurately
> >>is impossible. Far too many variables. Even within the same day.
> >

> >Well, quite, but you can make a reasonable estimate. Hence my 60-65%.
> >We're not looking for three-decimal-place accuracy! My point still
> >stands. The heat from a gas ring that doesn't go into the water goes
> >into the kitchen. The heat from a power station furnace that doesn't go
> >into generating electricity goes up the chimney.

> Steam from the cooling towers, Shirley?

water vapour -

[Dave Plowman (News)]

In article <8cqambphniasqqt03...@4ax.com>,
Chris Hogg <m...@privacy.net> wrote:

> On Sat, 18 Jun 2016 15:47:25 +0100, "Dave Plowman (News)"
> <da...@davenoise.co.uk> wrote:

> >In article <n4lamb91spnakit6p...@4ax.com>,
> > Chris Hogg <m...@privacy.net> wrote:
> >> Well, quite, but you can make a reasonable estimate. Hence my 60-65%.
> >> We're not looking for three-decimal-place accuracy! My point still
> >> stands. The heat from a gas ring that doesn't go into the water goes
> >> into the kitchen. The heat from a power station furnace that doesn't
> >> go into generating electricity goes up the chimney.
> >
> >That assumes all power generation is by gas. Or, indeed, heat.
> >Then there's how much energy is needed to get the gas out of the ground,
> >transport it, etc.

> Assumes nothing of the sort. My point still stands. The reason a
> kitchen gets hot when boiling a kettle with gas but not with
> electricity is because the waste heat from generating electricity is
> dissipated elsewhere.

Sorry - but don't get that. Suppose I have suitable solar panels and the
sun is shining and I use that electricity to boil the kettle? Or lived in
a country where much of the power is hydro?

--
*What do little birdies see when they get knocked unconscious? *

[Dave Plowman (News)]

In article <1tvambdh2dkuh3b6a...@4ax.com>,

Chris Hogg <m...@privacy.net> wrote:
> >> Assumes nothing of the sort. My point still stands. The reason a
> >> kitchen gets hot when boiling a kettle with gas but not with
> >> electricity is because the waste heat from generating electricity is
> >> dissipated elsewhere.
> >
> >Sorry - but don't get that. Suppose I have suitable solar panels and the
> >sun is shining and I use that electricity to boil the kettle? Or lived in
> >a country where much of the power is hydro?

> Then the total efficiency of the electric kettle would be much greater
> than that of the gas heated kettle. But the guy I linked to was saying
> that the total efficiencies, gas vs. electric, were about the same,
> because he was including the heat wasted in generating the electricity
> and from transmission lines, i.e. 64% was wasted, so he assumed was
> electric was only 36% efficient before it even got to his kettle. As I
> said in my post, the result you get depends on the initial assumptions

> you make, in this case on the efficiency of the generating and
> transmission process.

IMHO, he assumes too much.

How much energy is wasted pumping gas round the country? And in leaks?
If the turbines are blowing hard, gas use for generating reduces. And so
on. I'm also willing to bet electricity transmission losses are dependant
on distance.

These sort of figures tend to be produced to make some point or other.

--
*A day without sunshine is like... night.*

[jjjuu78]

"Tim Streater" <timst...@greenbee.net> wrote in message
news:180620161747358806%timst...@greenbee.net...
> In article <9ksambpgdivla5dqa...@4ax.com>, Chris Hogg
> <m...@privacy.net> wrote:
>
>>On Sat, 18 Jun 2016 16:46:24 +0100, Tim Streater
>><timst...@greenbee.net> wrote:
>>
>>>In article <n4lamb91spnakit6p...@4ax.com>, Chris Hogg
>>><m...@privacy.net> wrote:
>>>
>>>>On Sat, 18 Jun 2016 14:48:56 +0100, "Dave Plowman (News)"

>>>>Well, quite, but you can make a reasonable estimate. Hence my 60-65%.
>>>>We're not looking for three-decimal-place accuracy! My point still
>>>>stands. The heat from a gas ring that doesn't go into the water goes
>>>>into the kitchen. The heat from a power station furnace that doesn't
>>>>go into generating electricity goes up the chimney.
>>>

>>>Steam from the cooling towers, Shirley?
>>

>>'up the chimney' was just a turn of phrase. Wherever it goes, it
>>doesn't end up in DP's kitchen, unlike the waste heat when he boils a
>>kettle on gas.
>
> Roger that.

I wish you wouldn’t roger things in public, there are clearly children
reading here.

[bm]

"jjjuu78" <jjj...@nospam.com> wrote in message
news:dsm5a0...@mid.individual.net...

> I wish you wouldn't roger things in public, there are clearly children
> reading here.

Piss off Bosco.

[howard...@gmail.com]

Drink green tea, you only heat to 80C…a saving of 20% of normal cuppa and less energy wasted in evaporation and the eddy currents. Also less energy lost to kettle material and room as Delta with environment is lower. I'm pretty sure my induction pans don't get as hot as the kettle too ie they somehow transfer more of the energy to what's inside the pan. But induction pan lids are not sealed like a kettle

It really is a simple test, heat water in both, record time and temp change, and do watts X time comparison

[The Natural Philosopher]

On 04/06/2020 10:02, howard...@gmail.com wrote:
> Drink green tea, you only heat to 80C…a saving of 20% of normal cuppa and less energy wasted in evaporation and the eddy currents. Also less energy lost to kettle material and room as Delta with environment is lower. I'm pretty sure my induction pans don't get as hot as the kettle too ie they somehow transfer more of the energy to what's inside the pan. But induction pan lids are not sealed like a kettle
>
> It really is a simple test, heat water in both, record time and temp change, and do watts X time comparison
>

Ah. One of those people who thinks that heating the odd 350ml of water
20C less will save more than heating a whole 6000 cu ft house 0.1C less.

Once again the ability to Do Sums shows that saving money by heating
less water or water less is simply completely irrelevant in the context
of heating a whole house.

Especially since the heat in the water ends up in the house anyway. So
you are probably only looking at the marginal cost of heating it via
electricity rather than gas...or oil.

--
Labour - a bunch of rich people convincing poor people to vote for rich
people by telling poor people that "other" rich people are the reason
they are poor.

Peter Thompson

[Jack Harry Teesdale]

On 04/06/2020 10:02, howard...@gmail.com wrote:

> Drink green tea, you only heat to 80C…a saving of 20% of normal cuppa and less energy wasted in evaporation and the eddy currents. Also less energy lost to kettle material and room as Delta with environment is lower. I'm pretty sure my induction pans don't get as hot as the kettle too ie they somehow transfer more of the energy to what's inside the pan. But induction pan lids are not sealed like a kettle
>
> It really is a simple test, heat water in both, record time and temp change, and do watts X time comparison
>

It will be a spurious saving at best. Induction hobs are not a
particularly efficient method of heating water.

[Paul]

howard...@gmail.com wrote:
> Drink green tea, you only heat to 80C…a saving of 20% of normal cuppa and less energy wasted in evaporation and the eddy currents. Also less energy lost to kettle material and room as Delta with environment is lower. I'm pretty sure my induction pans don't get as hot as the kettle too ie they somehow transfer more of the energy to what's inside the pan. But induction pan lids are not sealed like a kettle
>
> It really is a simple test, heat water in both, record time and temp change, and do watts X time comparison

http://insideenergy.org/2016/02/23/boiling-water-ieq/

A microwave is about 50 percent efficient.
Most of the energy is lost in the process of converting electricity
to microwaves (which are part of the electromagnetic spectrum).

An electric stovetop is about 70 percent efficient,
although that varies widely depending on the type of pot or kettle
you use. Most of the energy is lost heating the air around the stove.

An electric teakettle is about 80 percent efficient, although again this
varies from kettle to kettle. Electric kettles are generally very well
insulated, and the heating coils sit directly in the water, so less
heat is lost to the air.

An induction stove or hot plate is about 85 percent efficient. It creates
an electromagnetic current directly in a pot to generate heat, losing
very little to the air.

To me, the results make no sense. Common sense.

https://www.aceee.org/files/proceedings/2014/data/papers/9-702.pdf

Table 2. Cooking efficiency results measured according to EPRI test procedure

Large Vessel Small Vessel

Half Power Full Power Half Power Full Power
Induction Cooker A 74.9% 77.6% 76.5% 77.4%
Induction Cooker B 75.7% 77.2% 75.6% 75.1%
Electric Coil 81.6% 83.4% 48.2% 41.5%
Natural Gas 41.7%* 35.2%* - 30.2%* <=== *bogus technique...
not that it matters

So the message here, is that electric kettle designers don't
give a rats ass about efficiency. If they did, they would beat
the induction design. The design of the vessel ("large" vessel
versus "small" vessel) is making a big difference to the
test result there.

This has been discussed in another context. Induction charging
for electric cars is proposed. However, the off-the-cuff analysis
for the induction technique, saw an additional 10% energy wasted
in the induction feature. Making it less attractive when
scaled to national scale. I would hope we continue to plug in
the cars, using the various connector designs, to save on that
10% waste. As that 10% waste could represent the entire output
of a single power plant (for nothing).

It's possible with an electric coil, to *completely insulate*
the test case. Resistive heating is 100% efficient (P=V*I type heating)
barring the usage of stupidly thin power cabling, leading up
to the element. If you had to, you could hard wire the heating
appliance, to reduce losses.

But the appliance designs are cheap, with the emphasis on
cheapness. Nobody is going out of their way to shave 5%
losses off a kettle.

Although the attempt to ban toasters was interesting... :-)
And that fight probably isn't over.

Paul

[Jack Harry Teesdale]

Interesting that those efficiency figures are for 'cooking efficiency'.

Induction heating by it's very nature does not have such a high
efficiency when you consider the actual eddy losses. ie power input v
power induced out.

[The Natural Philosopher]

On 04/06/2020 12:01, Jack Harry Teesdale wrote:
> Induction heating by it's very nature does not have such a high
> efficiency when you consider the actual eddy losses. ie power input v
> power induced out.

Oh dear. You don't know much electrical theory do you?


--
“Some people like to travel by train because it combines the slowness of
a car with the cramped public exposure of 
an airplane.”

Dennis Miller

[The Natural Philosopher]

On 04/06/2020 14:53, Tim Streater wrote:
> On 04 Jun 2020 at 13:35:05 BST, The Natural Philosopher <t...@invalid.invalid>

> wrote:
>
>> On 04/06/2020 12:01, Jack Harry Teesdale wrote:
>>> Induction heating by it's very nature does not have such a high
>>> efficiency when you consider the actual eddy losses. ie power input v
>>> power induced out.
>>
>> Oh dear. You don't know much electrical theory do you?
>

> Eddy losses? Eddy losses *where*, exactly?
>
Well exactly.

And if the power* in doesn't end up as heat, where the fuck is it going?


*As opposed to VA...


--
If I had all the money I've spent on drink...
..I'd spend it on drink.

Sir Henry (at Rawlinson's End)

[Dave Plowman (News)]

In article <rbag9r$kao$1...@dont-email.me>,

Jack Harry Teesdale <noreply49...@yahoo.co.uk> wrote:
> On 04/06/2020 10:02, howard...@gmail.com wrote:

> > Drink green tea, you only heat to 80CŚa saving of 20% of normal cuppa

> > and less energy wasted in evaporation and the eddy currents. Also less
> > energy lost to kettle material and room as Delta with environment is
> > lower. I'm pretty sure my induction pans don't get as hot as the
> > kettle too ie they somehow transfer more of the energy to what's
> > inside the pan. But induction pan lids are not sealed like a kettle
> >
> > It really is a simple test, heat water in both, record time and temp
> > change, and do watts X time comparison
> >
> It will be a spurious saving at best. Induction hobs are not a
> particularly efficient method of heating water.

I'd guess the thermal mass of a suitable pan much more of an issue than a
kettle? A plastic one will have very little.

--
*Eat well, stay fit, die anyway

[NY]

"The Natural Philosopher" <t...@invalid.invalid> wrote in message
news:rbavj3$htp$3...@dont-email.me...

> On 04/06/2020 14:53, Tim Streater wrote:
>> On 04 Jun 2020 at 13:35:05 BST, The Natural Philosopher
>> <t...@invalid.invalid>
>> wrote:
>>
>>> On 04/06/2020 12:01, Jack Harry Teesdale wrote:
>>>> Induction heating by it's very nature does not have such a high
>>>> efficiency when you consider the actual eddy losses. ie power input v
>>>> power induced out.
>>>
>>> Oh dear. You don't know much electrical theory do you?
>>
>> Eddy losses? Eddy losses *where*, exactly?
>>
> Well exactly.
>
> And if the power* in doesn't end up as heat, where the fuck is it going?
>
>
> *As opposed to VA...

Exactly. Both a kettle and an induction-heated pan will have some loss of
energy as heat that is radiated / conducted from the pan or which causes
convection heating of the surrounding air, but eddy "losses" are precisely
the way in which an induction pan heats the water.

Energy in => induction heating in pan ("eddy losses") + heat lost to
surroundings (radiation, convection and conduction)

[Tim+]

Four years after the question was asked....

Tim

--
Please don't feed the trolls

[NY]

"Dave Plowman (News)" <da...@davenoise.co.uk> wrote in message
news:587b648...@davenoise.co.uk...

> In article <rbag9r$kao$1...@dont-email.me>,
> Jack Harry Teesdale <noreply49...@yahoo.co.uk> wrote:
>> On 04/06/2020 10:02, howard...@gmail.com wrote:

>> > Drink green tea, you only heat to 80COa saving of 20% of normal cuppa

>> > and less energy wasted in evaporation and the eddy currents. Also less
>> > energy lost to kettle material and room as Delta with environment is
>> > lower. I'm pretty sure my induction pans don't get as hot as the
>> > kettle too ie they somehow transfer more of the energy to what's
>> > inside the pan. But induction pan lids are not sealed like a kettle
>> >
>> > It really is a simple test, heat water in both, record time and temp
>> > change, and do watts X time comparison
>> >
>> It will be a spurious saving at best. Induction hobs are not a
>> particularly efficient method of heating water.
>
> I'd guess the thermal mass of a suitable pan much more of an issue than a
> kettle? A plastic one will have very little.

If the object of the exercise is to bring the water to the boil and then
stop heating (eg when boiling water for a cup of tea) then I imagine thermal
mass is a significant factor. But for boiling vegetables, where you *keep*
the water boiling gently for tens of minutes, it may be less significant
because the pan will take longer to cool so the hob can be turned off
shortly before cooking needs to end.

I wonder how heat losses from a silvered steel pan compare with from a
plastic kettle.

[polygonum_on_google]

If you were designing a water heater, you could make the "kettle" out of plastic or glass and place a magnetic plate inside and entirely surrounded by water. An induction source outside would make that plate heat up. Which could be a neat approach.

I actually thought it was neat enough that you could have one kettle for water, another for milk. Both able to tell the base unit what temperature they were at. You could heat water for green tea, milk for baby, or whatever is needed, very accurately. Especially of the kettles had something to swirl the contents - also driven by the induction field.

[NY]

"polygonum_on_google" <magpie...@gmail.com> wrote in message
news:d8d2b103-d376-4985...@googlegroups.com...

>> Exactly. Both a kettle and an induction-heated pan will have some loss of
>> energy as heat that is radiated / conducted from the pan or which causes
>> convection heating of the surrounding air, but eddy "losses" are
>> precisely
>> the way in which an induction pan heats the water.
>>
>> Energy in => induction heating in pan ("eddy losses") + heat lost to
>> surroundings (radiation, convection and conduction)
>
> If you were designing a water heater, you could make the "kettle" out of
> plastic or glass and place a magnetic plate inside and entirely surrounded
> by water. An induction source outside would make that plate heat up. Which
> could be a neat approach.
>
> I actually thought it was neat enough that you could have one kettle for
> water, another for milk. Both able to tell the base unit what temperature
> they were at. You could heat water for green tea, milk for baby, or
> whatever is needed, very accurately. Especially of the kettles had
> something to swirl the contents - also driven by the induction field.

I haven't used our kettle for over a year, since we've lived in our new
house that has an Aga. I've got it down to a fine art: put pan of cold water
on the boiling plate (the hotter of the two hotplates), retrieve cafetiere
and cereal bowl from dishwasher (*) and put in a spoonful of coffee, put
cereals in bowl and stir in the milk, water is bubbling nicely by then so
pour over coffee, then put cereal in microwave - and start emptying rest of
dishwasher. All that makes me sound like a time-and-motion nerd who has
spent ages working out the critical path analysis ;-)

The last time we got the kettle out was when we had some building work and
the builders needed to make tea.

I never know about the economics of a gas-fired Aga versus a gas cooker or
electric cooker, but any waste heat keeps the kitchen warm so that
radiator's thermostatic valve rarely turns on. And it's great being able to
cook things *now* without having to wait for an oven to heat up.


(*) I get flak from my wife if I forget to empty the rest of the things in
it ;-)

[Tim Lamb]

In message <rbbmq0$p9e$1...@dont-email.me>, NY <m...@privacy.invalid> writes

I think this is an age thing.

Lots of us have had exposure to time and motion studies but I am
beginning to believe it comes down to making the best use of the time
you have left for routine activities.


--
Tim Lamb

[Vir Campestris]

On 04/06/2020 21:50, NY wrote:
>
> I never know about the economics of a gas-fired Aga versus a gas cooker
> or electric cooker, but any waste heat keeps the kitchen warm so that
> radiator's thermostatic valve rarely turns on. And it's great being able
> to cook things *now* without having to wait for an oven to heat up.

It may be different today, but the last few weeks our heating has been
off. Waste heat in the kitchen would be a damn nuisance.

My mum likes Agas - but she used to turn it off in hot weather.

Andy

[tabb...@gmail.com]

On Thursday, 4 June 2020 21:50:10 UTC+1, NY wrote:
> "polygonum_on_google" <magpie...@gmail.com> wrote in message
> news:d8d2b103-d376-4985...@googlegroups.com...

> > If you were designing a water heater, you could make the "kettle" out of
> > plastic or glass and place a magnetic plate inside and entirely surrounded
> > by water. An induction source outside would make that plate heat up. Which
> > could be a neat approach.

You could, but a traditional element would probably waste less and cost way less and last longer.

Or you could go the whole hog & make it a stinger kettle.

> I never know about the economics of a gas-fired Aga versus a gas cooker or
> electric cooker, but any waste heat keeps the kitchen warm so that
> radiator's thermostatic valve rarely turns on. And it's great being able to
> cook things *now* without having to wait for an oven to heat up.

ok in winter, dire in summer.

Re the 80 something % efficiency figure for kettles, I've always suspected it, it seems unlikely. Does the author have a motive for exaggerating a kettle's losses? IIRC yes.


NT

[NY]

"Vir Campestris" <vir.cam...@invalid.invalid> wrote in message
news:rbebtk$rtt$2...@dont-email.me...

Our house had both an Aga and a conventional electric oven fitted by the
previous owners. We've found that the extra heat given out by the Aga in hot
weather isn't a problem, mainly because we tend to have windows open anyway
(even to let out "greenhouse heat" from the sun) in hot weather. Our Aga has
AIMS, a system which allows you to control how much gas is used at different
time of day, so it allows the Aga to cool overnight and (when we weren't
working from home!) between breakfast and dinner. I always wonder how much
energy is used to maintain a constant temperature versus letting the device
cool down and then heating it back up to operating temperature. I think last
year we just turned the Aga down to minimum (we didn't have the courage to
turn it off completely in case we couldn't relight it!) for a week last
summer when it was very hot, and used the electric oven/grill, and a little
portable induction hob for veg.

Our central heating is "always on" in the sense that it *can* come on at any
time the temperature drops below what the thermostat is set to. During the
sunny period I think it came on once in early morning when the house had
cooled at bit overnight, but now the sun has gone, it's on every morning and
intermittently throughout the day as required. We have Hive controllers
(two, for radiators in two different "wings" of the house) and these allow
you to set different temperatures at different times of day - eg 20 during
daylight hours and 15-17 overnight. In winter, this will prevent the house
getting very cold overnight, while keeping it cooler at night than during
the day. The ability to control the heating from a mobile phone when away
from home is brilliant - when we go away on holiday we set the temp to about
10 deg (to prevent fridges/freezers getting too cold, since modern ones are
fussy about that) and then when we are a few hours away on our way back, we
turn up the thermostats to 20 so the house is warm for when we get home.

[NY]

<tabb...@gmail.com> wrote in message
news:d352648f-3c54-4cc4...@googlegroups.com...

> Re the 80 something % efficiency figure for kettles, I've always suspected
> it, it seems unlikely. Does the author have a motive for exaggerating a
> kettle's losses? IIRC yes.

A kettle will lose *some* heat by radiation and conduction to the air, but
I'd be surprised if it was as much as 20%. It's easy enough to work out how
much energy it takes to heat a known volume/mass water from about 10 degrees
up to boiling (assumed to be 100), and to measure the power consumption
(probably better than using the rated power on the appliance plate!). From
this you can calculate how long it would take to heat the water and compare
this with how long it actually takes.

I'll have to try it some time: I'll be intrigued by the result.

[Chris Green]

NY <m...@privacy.invalid> wrote:
> I always wonder how much
> energy is used to maintain a constant temperature versus letting the device
> cool down and then heating it back up to operating temperature.

That old chestnut! It *always* takes more heat to keep something hot
than to let it cool and then reheat it, basic physics. The heat lost
is proportional to the (4th power of?) the temperature so if it's hot
all the time it loses (a lot) more heat than if it's allowed to cool.

The better the insulation then the less the difference is, so if you
had 'perfect' insulation then there would be no saving if you turned
it off (and it wouldn't get any cooler if you did of course).

--
Chris Green
·

[tabb...@gmail.com]

On Saturday, 6 June 2020 12:56:25 UTC+1, NY wrote:
> <tabbypurr> wrote in message

There won't be any significant heat radiation at 20-100C.
Re convection/conduction losses, one way would be to boil the kettle, let it cool for say a minute then see how long to takes to reboil. I'll try it if I remember.


NT

[polygonum_on_google]

On Saturday, 6 June 2020 12:56:25 UTC+1, NY wrote:

I suggest that a lot of the waste is due to the combination of the physical mass of the kettle and excess water. All of which gets heated up - then slowly cools down. Probably reaching ambient shortly before its next use.

That was one of the reasons for my induction kettle idea. Very easy to keep down to minimum water and kettle mass.

[Max Demian]

On 06/06/2020 13:21, Chris Green wrote:
> NY <m...@privacy.invalid> wrote:
>> I always wonder how much
>> energy is used to maintain a constant temperature versus letting the device
>> cool down and then heating it back up to operating temperature.
>
> That old chestnut! It *always* takes more heat to keep something hot
> than to let it cool and then reheat it, basic physics. The heat lost
> is proportional to the (4th power of?) the temperature so if it's hot
> all the time it loses (a lot) more heat than if it's allowed to cool.

Heat loss is proportional to temperature difference, under conditions of
forced convection.

--
Max Demian

[Vir Campestris]

On 06/06/2020 12:51, NY wrote:
> We've found that the extra heat given out by the Aga in hot weather
> isn't a problem, mainly because we tend to have windows open anyway
> (even to let out "greenhouse heat" from the sun) in hot weather.

You paid for that heat, and now you are letting it out of the window.

Andy

[The Natural Philosopher]

As an example of wasting enormous effort to achieve no worthwhile
savings, this has to match a buyer I knew once who spent three weeks
getting a 0.1p reduction of the price of resistors, that totalled less
than a pound in total component cost in a £250 value item


--
“The fundamental cause of the trouble in the modern world today is that
the stupid are cocksure while the intelligent are full of doubt."

- Bertrand Russell

[Dave Plowman (News)]

In article <rbgrn3$h8t$1...@dont-email.me>,

The Natural Philosopher <t...@invalid.invalid> wrote:
> As an example of wasting enormous effort to achieve no worthwhile
> savings, this has to match a buyer I knew once who spent three weeks
> getting a 0.1p reduction of the price of resistors, that totalled less
> than a pound in total component cost in a £250 value item

Look after the pennies and the pounds look after themselves is a very apt
proverb in business. Now remind us of just how successful yours was?

--
*Why is it that most nudists are people you don't want to see naked?*

[Vir Campestris]

On 06/06/2020 20:44, The Natural Philosopher wrote:
>
> As an example of wasting enormous effort to achieve no worthwhile
> savings, this has to match a buyer I knew once who spent three weeks
> getting a 0.1p reduction of the price of resistors, that totalled less
> than a pound in total component cost in a £250 value item
>

How many did you make?

If you made a million items he just saved nearly a million quid...

Andy

[Dave Liquorice]

On Mon, 8 Jun 2020 21:11:49 +0100, Vir Campestris wrote:

>> As an example of wasting enormous effort to achieve no worthwhile
>> savings, this has to match a buyer I knew once who spent three
weeks
>> getting a 0.1p reduction of the price of resistors, that totalled
less

>> than a pound in total component cost in a £250 value item

>
> How many did you make?
>
> If you made a million items he just saved nearly a million quid...

eh? Please show your workings.

--
Cheers
Dave.

[The Natural Philosopher]

Er no. The TOTAL COST of the resistors was less than a pound. The saving
per set was a couple of pence


--
"When a true genius appears in the world, you may know him by this sign,
that the dunces are all in confederacy against him."

Jonathan Swift.

[Vir Campestris]

On 08/06/2020 21:29, The Natural Philosopher wrote:
> On 08/06/2020 21:11, Vir Campestris wrote:
>> On 06/06/2020 20:44, The Natural Philosopher wrote:
>>>
>>> As an example of wasting enormous effort to achieve no worthwhile
>>> savings, this has to match a buyer I knew once who spent three weeks
>>> getting a 0.1p reduction of the price of resistors, that totalled
>>> less than a pound in total component cost in a £250 value item
>>>
>> How many did you make?
>>
>> If you made a million items he just saved nearly a million quid...
>>
>> Andy

> Er no. The TOTAL COST of the resistors was less than a pound. The saving
> per set was a couple of pence
>
>

Ah. I thought you meant nearly a quids worth for each gadget.

In which case it was indeed a complete waste of time.

Especially since you seem to have made only a few tens of them.

Andy

[Dave Plowman (News)]

In article <rbu51n$mpb$1...@dont-email.me>,

Why would you bother employing a buyer for a low volume device?

--
*Some people are only alive because it is illegal to kill.