So, my wife bought me a Cosori CO108-NK electric kettle, and I am usually very skeptical about electric kettles in the US because the 120V electric supply means they are usually so slow.
But interestingly enough the Cosori is as fast as the 9000 btu/hr gas stove when I tested with 8 to 24 oz. samples brought up to boiling, sometimes slightly faster. At 32 oz the stove was much faster, though.
So, I am suspecting that what is going on here is that the Cosori has much less heat loss than typical electric kettles. How this works I am not sure, but I think some of it has to do with the weird shape of the kettle and some may have to do with the long thin spout and tiny cap airholes which do not let much vapour out when compared with other electric kettles.
Now, in terms of actual time to boil it's no better than the gas ring, but IT IS NO WORSE which makes it a marvel in the field when you don't have a gas stove handy. What is also handy is the shutoff at sub-boiling points so you can get water for green or oolong without having to keep an eye or an ear on the bubbles.
If I drank green tea regularly I would definitely want this even though I have the gas stove. If I had an electric stove I would definitely want it.
Recommended. Three stars. Joe Bob says you can drink it.
--scott
-- You can stop here but if you want to see the math you can keep going --
The gas range was an older Magic Chef with four 9,000 btu/hr gas burners, with a flat-copper-bottomed Revereware teakettle used. This would be equivalent to about 2650 watts of power or 37,100 cal/min although that power is not very well coupled into the heat load. No attempt was made to measure actual heat generation or measure gas consumption.
The Cosori measures only 10 amps at load, so 1200 watts or 16,800 cal/min.
8 oz:
250cc should take 20kcal to boil with no heat loss (starting at 20c) The stove took 1:45 to boil (65 kcal input to pot) The Cosori also took 1:45 to boil (29 kcal input to pot)
16 oz:
500cc should take 40kcal to boil with no heat loss (starting at 20c) The stove took 3:30 to boil (130 kcal input to pot) The Cosori took 3:40 to boil (61 kcal input to pot)
24 oz:
750cc should take 60 kcal to boil with no heat loss (starting at 20c) The stove took 5:10 to boil (191 kcal input to pot) The Cosori also took 5:10 to boil (87 kcal input to pot)
32 oz:
1000cc should take 80kcal to boil with no heat loss (starting at 20c) The stove took 6:20 to boil (233 kcal input to pot) The Cosori tok 7:00 to boil (118 kcal input to pot)
I think the discontinuity between 24 and 32 oz has something to do with higher heat loss from the smaller top section of the pot.