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).
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
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.
Heat loss is proportional to temperature difference, under conditions of forced convection.
You paid for that heat, and now you are letting it out of the window.
Andy
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?
How many did you make?
If you made a million items he just saved nearly a million quid...
Andy
eh? Please show your workings.
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
Why would you bother employing a buyer for a low volume device?
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