which uses less energy....a micowave oven or an electric kettle?

Question

my husband likes to heat water for tea in the microwave. i like to use the electric kettle, which i believe uses less electricity and saves energy. he says it doesn't matter. who's right?

Answer 1

The microwave should use a little less power, because it does not heat some of the water to boiling and let it escape as steam (which means heat loss).

Answer 2

Probably the kettle is more efficient, since the magnetron in the microwave converts only 75% or so of the input energy into microwaves - the rest is blown out as hot air, and does little or nothing to help heat the water.

But there is no need to guess. Why not make an experiment and find out?

1) look at the kettle and the microwave to find out how much power each one requires in watts. This information is always required to be listed on any electrical appliance.

2) Put equal amounts of water at room temperature into the microwave and the kettle. The amount of water should be similar to what you would normally use, i.e. one or two cups.

3) With a stopwatch, time how long it takes each device to heat the water to a rolling boil

4) multiply seconds x wattage to find out how much energy was used. If you started with equal amounts of water at equal temperature, the device with the lower seconds x watts product is more efficient.

The experiment will be a little bit skewed because the result for the kettle includes the energy needed to heat the kettle, and the result for the microwave includes the energy needed to heat the container for the water. But the specific heat of water is so high compared with most metals and ceramics that if you use a reasonable amount of water (at least 1 cup) these other effects will be pretty small.

Answer 3

In a microwave oven, the line power must be converted to microwaves, which involves some inefficiency not inherent in the kettle. However, the resulting microwave energy directly heats the water to be consumed and little else.

On the other hand, the power from the kettle goes directly into heat, so there is no inefficiency in converting to microwave power. However, that heat gets used up in heating up the kettle itself, the unused water, and possibly the surrounding air.

This is a tough call to make. If you use all of the water in the kettle to make your tea, the kettle would probably be more efficient; but if you heat more water than you use immediately, the balance may tip in favor of the microwave.

It would be an interesting experiment to try, and you can do it. First, turn off any air conditioning, refrigerators, freezers, or any other load in your house that may turn on or off or otherwise vary during the course of the experiment. Have one person stand by the watt-hour meter going into the house that the power company reads for your monthly bill, keeping eye on the meter wheel that drives the dials and pointers. Have the other person standing by to make the tea.

When the wheel gets to a convenient point, have the meter reader signals the tea maker to start heating the water to make tea. While the water is heating, the meter reader keeps track of the number of revolutions (and partial revolutions) that the meter's wheel makes. When the water is boiling and the kettle or microwave is shut off, the tea maker shouts a signal to the meter reader to stop counting and record the revolutions.

For best accuracy, a third reading of the meter should be taken for a time approximating that required to make tea. The times between the start and stop signals should also be noted for each tea-making process and the difference noted. This allows compensation for any offsets in the readings from other power loads in the house, multiplied by the time difference between the two ways to heat the tea water.

Answer 4

In answer to your question the microwave will only heat the amount you need and the cup too so there is no need to pour away water in order to preheat your cup or kettle etc. I will include a link with an answer to your question near the bottom of the page. Following that will be my starting commentary that I have kindly edited to the bottom of the page here. Hope you enjoy.

http://michaelbluejay.com/electricity/cooking.html

Have you ever noticed that a microwave oven can superheat water? When I get my cup of hot water from the microwave it continues to boil for a short while after-ward. If you drop the tea bag in straight away the water around the tea bag boils violently for a second or two before just being hot. My theory is that since microwaves heat water by spinning the water molecules the electric charge separation in each water molecule makes it behave like a tiny magnet that keeps it separate from neighbouring water molecules that spin in the same direction and thus reinforce each others magnetism while opposing fields would cause collisions that convert the spin energy to Brownian motion (rise in temperature). Any larger molecule "contaminant" disrupts the magnetic fields causing immediate conversion to heat energy (with a boiling over effect).

Answer 5

I would imagine the electric kettle is more economical as the heater is immersed in the water whilst waves just bounce around in the microwave. On top of that you must have noticed that the water heated in a microwave has a peculiar taste due the method of heating(molecular agitation). Personally I would not use a microwave for this purpose on a regular basis.

Answer 6

I would think the electric kettle since you really only have to heat a little coil inside whereas a microwave you have to power a whole unit to produce microwave energy. But I am just hypothesizing here.

It may not matter in the end because both are not typically used for long periods of time.

Answer 7

Do the math. see how long it takes to in the microwave then how long it takes on the kettle.

How many watts is the microwave how many watts is the kettle.

I would guess the kettle takes more energy.

Answer 8

It depends upon the wattage and how long will it takes for the water to boil.

Answer 9

depends on how long you are using the microwave for.