Hi all.
I thought I would share with you my thoughts on reducing energy usage.
First of all, you have to know what you are actually using.
I like tea.
A lot.
But how much energy does it cost to heat enough water for a mug of tea?
Time for an experiment.
Starting with a cold kettle, my daughter and I measured out 500ml of room-temperature (20 C, 68F) water and put it in the kettle. That is enough for two mugs of tea.
We then timed how long it takes to boil (the kettle as a "auto cut-off", so we used that to end the test).
It took us 68 seconds.
A few hours later, when everything was cool and stable again, I repeated the experiment with 250ml of water (still at 20 C, 68F)
Now it took 40 seconds.
We have a 3KW "flat plate" kettle.
On the assumption that the full 3 KW was being drawn for the time the kettle was on:
3KWx 40s = 2KWmins = 1/30 KWh.
My electricity tariff charges 13.53p per KWh
so 13.53 divided by 30 = 0.451p per cup of tea.
Now that assumes that I boil just the "right amount" of water each time.
What actually happens is that I don't measure the water with a graduated jug (as I did for the experiment), but I estimate the amount needed.
So I actually put more like the "two-cup" amount in for one cup.
In reality then, I use approx 3 kW x 68seconds x 13.53p/KWh
Which is 0.7667p per cup.
So, providing I only boil a cup or two of water each time I make tea, that really isn't going to be much of a usage.
Must do some more experiments on how much it costs to boil, say, a half-full kettle of water, rather than just one or two cups worth.
The great advantage of a "jug" kettle is that the user can boil just a small amount of water, and that small amount is reduced even further if the kettle has a flat element in the bootom, rather than the "traditional" coil that needs to be covered.
But, as even the one-cup/two-cup experiment above demonstrates the ACTUAL energy saving depends on the way the kettle is used as well as its intrinsic design features.
So why not try out a similar experiment with your kettle?
What will you discover?
Update 8th January 2015:
I filled the same kettle with a measured 750 ml of water at room temperature.
Being January, although our house has the heating on, the kitchen may be a bit colder than it was when I did the experiments mentioned above.
Anyway, I came up with the figure of 102 seconds for the 750 ml of water.
So, with three data pairs, I have enough to draw a graph:
What could be done to improve the experiment?
Well, for a start the various tests could be repeated many times, just to check the results are consistent.
I could also have formally measured the water temperature in the jug, just to make sure it is at the 20C (68F) I have assumed.
But this isn't about me - it is about you doing your own experiments, and hopefully saving energy as a result of what you learn.
I thought I would share with you my thoughts on reducing energy usage.
First of all, you have to know what you are actually using.
I like tea.
A lot.
But how much energy does it cost to heat enough water for a mug of tea?
Time for an experiment.
Starting with a cold kettle, my daughter and I measured out 500ml of room-temperature (20 C, 68F) water and put it in the kettle. That is enough for two mugs of tea.
We then timed how long it takes to boil (the kettle as a "auto cut-off", so we used that to end the test).
It took us 68 seconds.
A few hours later, when everything was cool and stable again, I repeated the experiment with 250ml of water (still at 20 C, 68F)
Now it took 40 seconds.
We have a 3KW "flat plate" kettle.
On the assumption that the full 3 KW was being drawn for the time the kettle was on:
3KWx 40s = 2KWmins = 1/30 KWh.
My electricity tariff charges 13.53p per KWh
so 13.53 divided by 30 = 0.451p per cup of tea.
Now that assumes that I boil just the "right amount" of water each time.
What actually happens is that I don't measure the water with a graduated jug (as I did for the experiment), but I estimate the amount needed.
So I actually put more like the "two-cup" amount in for one cup.
In reality then, I use approx 3 kW x 68seconds x 13.53p/KWh
Which is 0.7667p per cup.
So, providing I only boil a cup or two of water each time I make tea, that really isn't going to be much of a usage.
Must do some more experiments on how much it costs to boil, say, a half-full kettle of water, rather than just one or two cups worth.
The great advantage of a "jug" kettle is that the user can boil just a small amount of water, and that small amount is reduced even further if the kettle has a flat element in the bootom, rather than the "traditional" coil that needs to be covered.
But, as even the one-cup/two-cup experiment above demonstrates the ACTUAL energy saving depends on the way the kettle is used as well as its intrinsic design features.
So why not try out a similar experiment with your kettle?
What will you discover?
Update 8th January 2015:
I filled the same kettle with a measured 750 ml of water at room temperature.
 |
| The water is measured out ... |
 |
| ... and poured into our "flat plate" jug kettle |
Anyway, I came up with the figure of 102 seconds for the 750 ml of water.
So, with three data pairs, I have enough to draw a graph:
What could be done to improve the experiment?
Well, for a start the various tests could be repeated many times, just to check the results are consistent.
I could also have formally measured the water temperature in the jug, just to make sure it is at the 20C (68F) I have assumed.
But this isn't about me - it is about you doing your own experiments, and hopefully saving energy as a result of what you learn.
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