Steve Whitehorn

iTrader: (13)

My Mum and Dad are living in the dark ages. Born in the 30s etc ...you get the picture. Now...

They only use gas in their kitchen. So for toast their grill is brutaly efficent - you can see that it far more cost effective than an electric toaster could ever hope to be.

Now on to the cup of tea - of which they drink rather a lot.
At the moment they heat up an old school kettle on their gas stove. Would an electric kettle be a cheaper option for them?

Does electricity cost more than gas?
Anyone know the answer

Stainy

I was always told that electricity is significantly more expensive than gas....Hence you don't use the immersion heater much on the hot water tank....gas all the way???

CrisPDuk

We've gone back to a cooker powered kettle (with a whistle) for two reasons;

1/ The average electric kettle doesn't seem to last much above 18 months these days

2/ We were forever turning the kettle on, then walking away to do something else and forgetting to actually brew up, thus the kettle usually needed to be boiled twice for each brew

So in our case gas power is definitely better than electric

LG John

I hope someone does some calculations on this. I'm a nerd and it'll make for good reading. My initial thought is that whilst electricity is, technically speaking, more expensive boiling a kettle with gas may cost more in the long run. My logic is this: the electric element is immersed in the water and therefore most of its energy is directly absorbed by the water. However, a metal pot/kettle placed over a gas flame causes much of the flame and heat to pass around the side of the kettle and into the atmosphere. Furthermore, the base of the pot/kettle absorbs a lot of the heat meaning that far less of the energy is making its way to the water. Whether this alone is enough to swing the electricity vs gas argument.....I don't know

kingofturds

iTrader: (1)

A few years ago we used to have this right tight git at work. He would shower/shave at work, and at the end of the he would boil the kettle and take a flask of hot water home with him

Think I may take a leaf out of his book

ricardo

There is definitely a lot more heat wasted when using a kettle on a gas hob. In the winter it isn't really wasted, since it will help to warm the house.

The electric one is safer in that it cuts off, leaving one on the gas can be seriously bad news. The gas one may be able to boil smaller quantities of water compared to a normal electric one, although some electric ones have a flat element in the base.

I doubt whether it is worth worrying about, there are probably other things like insulation in the house that would make a much bigger difference.

Chip

Gas is much cheaper.

Chip

g7prs

iTrader: (5)

Yes but what is quicker at say boiling a litre of water? You really need to find out how long it takes to boil the same amount using both methods and then work out the costs.

Chip

Basically, the amount of energy needed to get to water to boiling doesn't change. It can be calculated from knowing the initial temperature of the water, the final temperature (100 c), and the specific heat capacity of the water.


Chip

CrisPDuk

Just go to the cupboard and watch the electric meter spin like a CD when you switch the kettle on

The gas may take slightly longer, but the meter isn't half as scary

ScoTTyB

I liked the sound of this, so did these calculations on the back of my *** packet this afternoon.

Electric kettle vs boiling water on the hob
As an experiment I tried different ways of boiling 0.5 litre of water (measured using a small measuring jug).

N.B. 1kWh=3600kJ (because by definition 1 Watt is 1 Joule per second, and there are 3600 seconds in an hour).
Plastic electric jug-kettle (2200W rating)
Time to boil: 1m40s (100 seconds)
Energy used: 100s×2200J/s = 220000J = 220kJ
220kJ / 3600kJ/kWh = 0.061 kWh. Using 0.54 kgCO2/kWh gives 33 grammes CO2
Small-sized electric hob at full power (1200W rating)
In medium/small aluminium saucepan weighing 0.374kg
Time to boil: 9m00s (540 seconds) for vigorous boil [8m00s for begin to boil]
Energy used: 540s×1200J/s = 648000J = 648kJ
648kJ / 3600kJ/kWh = 0.180 kWh. Using 0.54 kgCO2/kWh gives 97 grammes CO2
Medium-sized gas hob burner at full power (2000W rating)
In medium/small non-stick aluminium saucepan weighing 0.337kg
Time to boil: 6m00s (360 seconds) for a decent rolling boil [5m20s for lazy bubbling boil]
Energy used: 360s×2000J/s = 720000 = 720kJ
720kJ / 3600kJ/kWh = 0.200 kWh. Using 0.19 kgCO2/kWh gives 38 grammes CO2

The electric hob is easily the worst option, costing three times as much energy and CO2 as the kettle. Although the gas hob still results in almost three times as much energy (heat) being delivered to the home, this comes at very little extra CO2 cost. If that warmth is useful to you, then why not? On the other hand, because the hob takes longer you're more likely to forget about it and/or leave the water boiling for longer than necessary, which uses more energy and will also put more humidity into the house. Further considerations might include whether using a saucepan is going to result in extra washing-up, and whether you really want the extra humidity from the burner and drying the saucepan afterwards...

Chip

All depends on the KW/h cost of which the gas is a lot lower.

Chip .

Steve Whitehorn

iTrader: (13)

Excellent Stuff
Scoobynet at its best

ScottyB

Two more factors -
The gas is never left on for longer than necessary
And the water is in a kettle - the whistling type

Your impressive stats seem to suggest that Electric Kettle is the best, when the consensus is gas is the most cost effective!

I posted this out of curiousity really. But given how many cups of tea we get through coupled with energy prices it could make a difference.

ronjeramy

iTrader: (1)

what about low watt kettles?

ronjeramy

iTrader: (1)

Oh and Steve are you Scottish per chance?

LG John

That's all very well but the key variable is the amount of energy that is actually getting to the water. With a submerged element vs an external flame on the otherside of a metal casing the efficiency is going to differ greatly.

Scotty's experiment demonstrates this well and despite the cheaper price of gas I still stand by my guess that a kettle is cheapest.

By the way if your parents are that tight why not get them to chop down some trees, rig up some sort of frame and hang a pot over an open fire

Steve Whitehorn

iTrader: (13)

LOL

Low watt kettles....thats an added complication I didn't need.

Steve Whitehorn

iTrader: (13)

Thats a good idea SB - I will put it to them

Shark Man

We've gone tight-****....if I want a mug of tea...I boil a mug of water.

Beauty is, with a 3kw kettle, I get a cuppa within 30seconds. And don't waste 3mins worth of eleccy boiling 1 litre of water that I'm not going to use.


For cooking we use gas, actually bought a nifty energy saver for the sunday lunch: A hob powered steamer, patatoes in the bottom with the water, and veg in the next two tiers....so we use 1 hob on low to cook all 3 veg, as opposed to using 3 hobs.

warrenm2

ok I'll have a go at this (also using the convention of . means multiply and · is the decimal point)

Etotal = m.c.⌂T.µ

where

m=mass of water (g)
c=specific heat capacity of water (J/K.cm³)
⌂T=temperature change in water (K)
µ=efficiency of heat transmission from heat source to fluid (dimensionless)

(Note that c is related to volume but as water has a density of 1 am using ml/cm³/g interchangeably )

Assume that :-

m=400g (to cover that a mug would be less than that but you never boil the exact amount, you always have a bit more)
c=4·184 J/K.cm³
⌂T= 85 (assume tap water is at 15°C and it obviously boils at 100°C)
µ = 0.9 for electric flat element in a kettle and 0·7 for gas hob. I have no evidence to back these figures up, they are simply rough guesses. Due to the way these are used they need to be reciprocals (ie Ive expressed them as percentages)

The rating of the kettle or hob doesnt matter substantially, it is more to do with the speed at which energy is put in the water, not the total amount of energy consumed. (there will be some effect with low powered heaters due to the fluid having more time to cool but this will be small and hence ignored)

So we have Etotal=400.4·183.85.1/0·9=158kJ for electric kettle and Etotal=400.4·183.85.1/0·7= 203kJ for gas hob.

Now for the cost of these. As mentioned above 1kWh = 3600kJ.

Typical prices I found were gas = 3·453p per kWh and leccy = 12·66p per kWh

Therefore price to boil a cuppa on

gas = 203.3·453/3600 = 0·195p
leccy =158.12·66/3600 = 0·555p

Surprised at the kettle one, but HTH

sarasquares

iTrader: (1)

no one mentioned heating the water in a microwave

Scoobychick

iTrader: (1)

It's threads like this that remind me what a bunch of nerds we all are on Scoobynet

alcazar

iTrader: (2)

Beat me to it: under 1 minute at 700W to bring EXACTLY one mug of water to the boil

I make that under 42kJ.

Alcazar

Mitchy260

Anyone tried boiling the water in the microwave and working out its relevant cost

Scoobychick

iTrader: (1)

OK nerds, so what about my coffee machine? How does that compare? Here are the stats:

1260W

It pushes approx 100ml of hot water through at a pressure of 19 bar

Frother then pushes steam through to heat and froth the milk

It's switched on all day and keeps the water to a certain temp all day, I don't know what that is but I'm sure you lot can work it out

oldsplice

Are the teabags re-used?

Leslie

Depends on the size of the kettle base in relation to the flame width really. Most kettles have a pretty broad base for that reason.

The metal tubing surrounding the electric element would also absorb some of the heat as you say the kettle base does, however it seems to me that most of that energy will be transferred to the water in each case.

I feel that the biggest factor will be the relative costs of electricity or gas.

Les

AndyC_772

iTrader: (2)

Sal,

There's no way to know how much energy it uses maintaining a constant temperature, since that depends on the rate at which is loses heat to its surroundings - which is an unknown.

I have one of these: Maplin > Plug-In Mains Power and Energy Monitor - which would tell you very quickly how much energy it's using.

I did compare the amount of energy taken to make a cup of instant coffee using the kettle with the amount of energy used by the capuccino machine. There was very little difference.

Brun

What about the stats using one of these? I know they don't boil water as such, but they do provide a drink which imo is hot enough to be included in this thread

scoobyster

My colleague used to work testing cookers and was waxing lyrical about induction hobs yesterday after I asked him for advice on what type of cooker to get. I'd guess these would be a pretty efficient way to make a cuppa since they heat the water rather than the pan, much like a microwave.

As an aside, he recommended I get a 'domino' hob arrangement of 2 gas and 2 inductions hobs: gas being better for frying and elec for boiling. He didn't know about ovens though; anyone have views on this - gas or elec?