Cook Top Shootout!
I did some energy use comparison experiments this morning, and I thought I'd share the results.
The tests consisted of heating two pounds of water (very carefully measured) from 53F degrees to a rolling boil (212F). I used the same pot in each test, and re-cooled the pot before the next test. The power was monitored with a Kill-a-Watt, and I also used a kitchen timer to time how long it took to reach boiling.
I tested three cook tops, the first was a resistance cooker that had a measured wattage of around 900 watts.
The second was an induction cooker, 'Aroma', I bought from Target. It is sold as a 1500 watt cooker, but it's maximum power draw was about 1300 watts. In the tests, I reduced the power level to as close as I could get to 900 watts, which measured to be about 940 watts.
The third was an induction cook top, 'Avantco', I bought online. It is sold as a 1800 watt cooker, but had a maximum power draw of about 1500 watts. In the tests, I reduced the power level to as close as I could get to 900 watts, which measured to be about 860 watts.
Test Run #1:
Resistance Cook Top (aprox 895 watts)
Time to boil 2 pounds of water: 14 minutes
Kwh consumed: .2
Time for boiling to stop: 4 minutes
Avantco Cook Top (aprox 940 watts)
Time to boil 2 pounds of water: 10' 45"
Kwh consumed: .15
Time for boiling to stop: 6 seconds
Accent Cook Top (aprox 850 watts)
Time to boil 2 pounds of water: 9' 10''
Kwh consumed: .14
Time for boiling to stop: 9 sec
Test Run #2:
Resistance Cook Top (aprox 895 watts)
Time to boil 2 pounds of water: 14 minutes
Kwh consumed: .21
Time for boiling to stop: 4 minutes
Avantco Cook Top (aprox 940 watts)
Time to boil 2 pounds of water: 11' 00"
Kwh consumed: .15
Time for boiling to stop: 9 seconds
Accent Cook Top (aprox 850 watts)
Time to boil 2 pounds of water: 9' 00"
Kwh consumed: .14
Time for boiling to stop: 7 seconds
* * *
The 'Watts' reading on the Kill-a-Watt was very stable when measuring the resistance heating device, but was varying when measuring either of the induction heating devices. So the wattage readings from the induction units should be considered approximate. The Kwh readings, on the Kill-a-Watt, on the other hand, are cumulative so should be considered to be more reliable.
It is clear that water was heated much faster on either of the induction cookers than on the resistance cooker, in fact in about 70% of the time. Also, cool down time was very much faster on the induction cookers, calculated as about 3% of the time of resistance, compared to the resistance cooker.
Looking at the power used, it is also clear that the induction cookers used less power to heat water, in fact, about 75% of the power that was used by the resistance cooker, compared to the resistance cooker.
One explanation of the differences can be found in the cool down times, because the resistance cooker has substantial additional thermal mass to heat as it is heating water.
So, if cooking was done on a continuous basis, induction cooking might not show the same benefits as it does when we cook small batches.
But we actually cook in small batches almost all the time.
But interestingly, the cheap induction cooker heated the water fastest, while using least power... and it is much quieter. All very good qualities.
EDIT: Oh, and one more thing, a subsequent reader did the math on efficiencies, here's what he said:
Quote:
Originally Posted by ELGo
Ignoring the container, the water took up 88 * 900 * 4.2 = 332640 Joules = 0.0924 kwh. This works out to 66% efficiency for the better induction device, and 46% for the resistive device.
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Best,
-AC