Electric Kettle or Gas?

Frondorddu

I know that electric kettles use a lot of electricity and have always assumed that gas is cheaper but as that keeps going up am not so sure now.

Desperate_Housewife_2-2

gas and electric prices have changed recently and I wonder if anyone has any more info about which is cheaper to use, gas or electric kettles?

I have had electric kettles and mine broke last year so i went back to my gas hob one. My gas bill is £65 this month and lec is £50 I a trying to save money and thought buying an electric kettle might be better, what does everyone else think?

Ben84

Desperate_Housewife wrote: »

gas and electric prices have changed recently and I wonder if anyone has any more info about which is cheaper to use, gas or electric kettles?

I have had electric kettles and mine broke last year so i went back to my gas hob one. My gas bill is £65 this month and lec is £50 I a trying to save money and thought buying an electric kettle might be better, what does everyone else think?

Interesting question, and as my electric costs have gone up I decided to calculate approximately how much it costs each time I use my electric kettle.

I have an entirely ordinary 3000w swan kettle with a submerged element, it's quite a large one compared to many modern kettles as it took 1.5 pints to fill it to the minimum level that covers the element sufficiently. This much water would make three mugs of drinks. I filled it with cold water from the tap (sorry, not sure how cold), turned it on and it took 224 seconds before it boiled and switched itself off.

So, I need to turn the known wattage of the kettle and the time it ran for in to watts consumed. The three thousand watts printed on the base means it would use three thousand watts if heating constantly for an hour. However, it heated for 224 seconds. There are 3600 seconds in an hour, so 3600 / 224 = 16 instances of 224 seconds in an hour. From here to find the watts used, 3000 / 16 = 187.5 watts to boil 1.5 pints of water.

I'm billed in kWh, so to turn 187.5W in to a value in kWh, 187.5 / 1000 = 0.1875 kWh. Multiplying this by my cost per kWh, 0.1875 x 0.11 = 0.02. So, 2p to boil the kettle. This is about the same as using a 60W lightbulb for three hours and proves that the electric kettle is a cheap item to use. It may or may not be cheaper than using the gas hob, but I think for gas we would also be looking at a similarly small price of a few pence. From this, even if we discover the electric kettle is cheaper, I don't think it would ever pay for itself in a practical time. You might still want to buy one however as they're fast and most of them turn themselves off when they boil, so you don't have to watch them.

IanMcL

My solar panels are great and most things are 'free' to run during the day, if the sun shines. The exception is the electric kettle, which is a 3kw burst of energy and therefore uses grid as well as self generated.

At night, it is all pay out as there is no sun!

I got talking to my wife about it and we thought about the gas hob kettle. Hence, why I am here!

Great arguments. Thanks. I think a gas comparison like the last electric cost of 2p per boil, is needed. The best for me during the day would be for a 2kw burst of power from an electric kettle! That would then be free. I had thought of the gas for the evening but unsure of the cost equation.

MartinN_2

Hi Ben 84, you say "This is about the same as using a 60W lightbulb for three hours". I can't believe that anyone on this forum still uses an old fashioned incandescent light when CFLs (low energy bulbs) are so cheap and LEDs are coming down in price.
Back to main issue, my hunch is that electric kettles are more efficient with the much greater efficiency of heat transfer exceeding the inefficiency of elec generation.
I have used my plug in energy meter to observe that solid element kettles are more efficient than curly element ones, dramatically so for boiling just one cup of water.
BUT in winter a gas hob is more efficient because you benefit from the "wasted" heat around the edge of the kettle.

larkim

I've often quoted the "all heat is good heat in the winter" argument in discussions, but thinking about it this can't always be taken to be a good argument.

For example, many people will not be spending much time in the room which has been heated up after a kettle has boiled (typically the kitchen). So you might use your gas to boil the kettle, bring the temp of the kitchen up a small amount, then leave the room and sit down in the lounge. The thermostat controlling your central heating might well be in the hall or somewhere else unconnected with the rise in temp of the kitchen, and unless you have a highly temperature sensitive heating system in the kitchen, the kitchen will not "demand" any less heat from the supplying system. So all you'll end up with is a kitchen which is slightly warmer than it usually is, which will then overnight lose the heat from the whole house system (via windows, walls, floors etc) and you'll have wasted that energy.

Does that make sense?

Matt

Ben84

MartinN wrote: »

Hi Ben 84, you say "This is about the same as using a 60W lightbulb for three hours". I can't believe that anyone on this forum still uses an old fashioned incandescent light when CFLs (low energy bulbs) are so cheap and LEDs are coming down in price.
Back to main issue, my hunch is that electric kettles are more efficient with the much greater efficiency of heat transfer exceeding the inefficiency of elec generation.
I have used my plug in energy meter to observe that solid element kettles are more efficient than curly element ones, dramatically so for boiling just one cup of water.
BUT in winter a gas hob is more efficient because you benefit from the "wasted" heat around the edge of the kettle.

The 60w bulb is just a popular measure of energy consumption that I think people understand. However, I do still use some around the house.

podcake

Hello All,

I wonder if I can help at all here.

Firstly, let me say theres a lot of confusion flowing through this board regarding this topic.

To offer the OP a definitive answer:

1) the ELECTRIC kettle will be MORE efficient than the GAS
2) depending on your various purchase prices the GAS will probably be cheaper. (this is because you will use in the order of twice the kWh but gas is often 1/3 of the cost per unit)

Basically, choose: Cost or 'Ecofriendlyness' (yes, i made the word up)

Source: Experimentation for my Postgraduate degree in 'Advanced Engineering'


now to address some of the confusion:

Ben84 wrote: »

So, I need to turn the known wattage of the kettle and the time it ran for in to watts consumed. The three thousand watts printed on the base means it would use three thousand watts if heating constantly for an hour. However, it heated for 224 seconds. There are 3600 seconds in an hour, so 3600 / 224 = 16 instances of 224 seconds in an hour. From here to find the watts used, 3000 / 16 = 187.5 watts to boil 1.5 pints of water.

I'm sorry to pick on you Ben84, but I have to say that you seem to be terribly confused here. (although your maths corrects itself along the way, and your result is correct).

Watts is NOT a measurement over time in the way that you say. A Kettle rated at 3000W does not use 3000W in an hour. It uses 3000W CONTINUALLY. if it ran full pelt for an hour it would use 3000 Watt hours.

Also, in reality, boiling the amount of water you want for JUST the cup of tea you require is not always the best way to go about it, mainly because of the laws of thermodynamics. In reality, you are best off heating the water to boiling AS FAST AS POSSIBLE and keeping it there through heat insulation. If anybody wants me to explain that further, ask and I'd be more than happy to go into some depth with you.

rogerblack

podcake wrote: »

Also, in reality, boiling the amount of water you want for JUST the cup of tea you require is not always the best way to go about it, mainly because of the laws of thermodynamics. In reality, you are best off heating the water to boiling AS FAST AS POSSIBLE and keeping it there through heat insulation. If anybody wants me to explain that further, ask and I'd be more than happy to go into some depth with you.

Unfortunately, your clarification is mislead.
If you heat a half a cup of water to 100C, you will use about 25 watt-hours. (80C*4180J/C/kg*0.25kg=23Wh)

This takes the same amount of energy if it's heated slowly or fast, unless heat leaks out while it's heating.

How much energy would it take to keep a kettle warm?

To keep a 2l kettle, with diameter 12cm, height 20cm warm, with a wall thickness of 1cm, and an insulation quality the same as good as decent house insulation:
Area = .08m^2
DeltaT = 80C
Thickness = 0.01m
Thermal resistance = 0.02W/m/C. (equal to Kingspan, or comparable PIR/PUR foams)
*
.08m^2*80C*.02W/m/C / .02W/m/C = 12W.

So, you can boil half a cup of water every couple of hours on the losses from keeping a well insulated kettle hot. (I question if you can buy a kettle this well insulated)

Your points on the gas kettle also neglect the extra ventilation needed to remove the humidity from the air from gas combustion.

celerity

If you really want to be efficient, you could decant cold tap water into a black jug and stand it on the window sill and use that water to fill your kettle. On a sunny day you should be able to help the kettle out by a few degrees .

/\dam