Why aren't kettles insulated?
1. Safer as the casing will not be as hot.
2. Less noise as the insulation would absorb the sound of the boiling water.
3. More economial/enivromentaly friendly as less heat would escape via the casing.
4. Quicker as the water in the kettle would retain heat for longer thus reducing reboiling time.
I can think of 2 disadvantages:
1. Cost. It would clearly cost more than current kettles.
2. For the insulation to be effective the spout would have to be sealed in some way. This would mean that pressure would build up inside the kettle.
The first of this disadvantages is unavoidable, but the second could be address by use of a pressure valve of some kind. Neither seem like show-stoping problems.
So why aren't kettles insulated? Is it that the current kettle is good enough? Am I under-estimating the cost factor? Or am I missing something?
Cheers
Ben
Answer:
A very good question, and one I have sometimes wondered about. What you say makes complete sense, yet kettles are never insulated. This leads me to suspect that the causes are either economic or totally irrational.
Leaving aside the irrational (such as "kettles just don't look like that"), what about economic factors? In other words, would an insulated kettle really save money?
I'm going to guess some numbers. Let's say it's a 1kW kettle and is typically used to boil 0.5 litre of water from a starting temperature of 20°C.
With perfect insulation, you can work out that the time to boil would be 500 × 80 × 4.2 / 1000 = 168 seconds. In reality it takes about 240s (4 minutes) so the energy lost is (240 – 168) × 1000 joule = 72kJ = 0.02kWh.
Now where I live 1kWh costs 9p (18 US cents) so the money saved per boiling by having perfect insulation would be 0.18p (0.36c). I would guess that even the best practical insulation would only reduce the losses by 50%, so the money saved would in reality be about 0.9p (0.18c).
Let's say you use the kettle twice a day for five years. The amount you would save with perfect insulation would be 0.9 × 2 × 365 × 5 = 329p = £3.29 ($6.57). So the insulation would have to add no more than this amount to the price of the kettle to make it worth having.
As an electric kettle costs about £15 ($30), the manufacturer would have to able to add insulation without increasing the price by more than about 3.29 / 15 × 100 = 22%. I doubt if this is possible. I think we have our explanation: adding insulation would cost more energy than it saves.
Of course, if kettles were built to last 10 years they would cost more in the first place, the additional cost of insulation would be a smaller percentage, and insulation would be worth having. But 10 years is seen as a very long time these days. Your idea is probably one for the (near?) future rather than the present.
Strangely enough, the best approach may be irrational: "Insulated kettles are just so coool..."
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If you insulate the kettle, how will you heat the water inside?
Insulation works *both* ways, keeps heat in and keeps heat out.
I think you have a good idea
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