I’m pretty sure there was a thread a while back comparing boiling times for one litre of water, and I’m sure I was the winner…although I no longer live in that house, so I’ve got a crappy kettle now.
Microwaves, on a shot blast of full power, give hot water, but not boiling. Not crucial for cocoa, but important for tea (the level of dissolved gas is the important thing there). Kettles, by their design, cannot waste much energy - apart from what goes as noise, or as heat that never reaches the water, they’re basically converting electricity into hot water. Flat-base ones seem to be the faster option, but are more expensive.
Space? Or a highly-efficient vaccum pump with a sealed vessel? (sorry. Taking a break from studying chem) Or, well, altitude? We need to adjust all our experiments in lab, because water boils at about 190F here (which is frustrating as hell when all you want is some late-night ramen!)
In a less-irritating note, I think - in my entirely ignorant capacity - that an electric-kettle type setup is most efficient. The more heating area in contact with the water, then the most heat for electricity used goes into the water, right?
Any inefficiency goes into waste heat, so the question really is: if you boil the same amount of water, which method warms up the room air by the least amount? My WAG is that hot pots (electric kettles) and microwave are about the same - neither appliance incorporates a cooling fan, and the outside surface gets warm to the touch but not hot.
Is it efficiency you’re looking for, or just the fastest boil? A Formula One car will get round a track pretty quickly but I bet my car gets better mpg.
I remember back at school comparing the energy required to boil the same amount of water - we compared an electric heater immersed in the water (like your kettle), and a bunsen burner under the water (like using the cooker). I can’t remember how we measured the amount of energy from the bunsen burner, but the electric heater was by far the more effecient - that is to say it consumed less energy than the bunsen to heat the same amount of water.
Unfortunately we didn’t measure microwave usage, but you should be able to do so:
Boil some water in the kettle, timing how long it takes to reach boiling point. Boil the same amount of water in the microwave, and time that too (start at the same temperature of water).
1kW * time for kettle = energy used by kettle
1.3kW * time for microwave = energy used by microwave
Whichever of these is the lower is the more efficient way to do it. Happy experimenting!
The microwave contains a large volume of air which can absorb a great deal of wasted energy before becoming ‘hot’. A kettle, however, has no such heatsink. If both get warm-yet-not-hot, it suggests the microwave is far less efficient.
A microwave oven uses a magnetron to convert electricity into microwave radiation. Since the magnetron has an conversion efficiency of about 70%, 30% of the electrical power is being wasted in heating the magnetron.
When you heat water using electricity you have to consider that the powerplant also has efficencies, along with the power distrubution system.
So all in all neither way is really that efficient. If you can heat it on a gas stove you will be far ahead, especially if it was in winter and the waste heat went to offset your heating bill,
You’re right - although the powerplant is converting the energy from coal or gas or oil or whatever to electricity on a very large scale - so the efficiency will be greater than if you were to do the same at home.
I like the idea of using the gas stove to heat your house with the waste heat, too
This is true. It’s also true that an electric stove’s heating element is 100% efficient.[sup]1[/sup] Therefore, an electric stove is much more efficient than a microwave oven, correct?
Well, not quite. While all the above statements are true, there’s a big problem with an electric stove: the thermal coupling between the heating element and the thing you want to heat sucks. When a teakettle is placed on top of an electric heating element, for example, how much of the energy is actually absorbed by the water? I don’t know, but a WAG would be 20%.
[sup]1[/sup] [sub]I’m referring here to the ratio of the thermal power produced by the heating element and the electrical power (I*V) consumed by the heating element. I am not taking the conversion efficiency at the power plant into account. This is the right approach, since both an electric stove and a microwave oven draw power from the power plant.[/sub]
Of course, if you heat the water during the summer, then you have to use even more power to pump that waste heat out of your house with an air conditioner.
Not sure I understand you here. The reason the microwave works so well to heat water is that water molecules are particularly good at absorbing the radio waves produced by the magnetron. While air is not at all good at absorbing this energy. And heat loss to the environment during heating due to conduction and convection is probably not worth mentioning, although you could always heat your water in an insulated mug if you were worried about it. So I think the air volume in the microwave is irrelevant.
According to this article, electric heat is most efficient, followed by microwave, and then by gas. With the caveat that you’re more likely to heat precisely the right amount of water in a microwave while you might fill an entire tea kettle on the stove.
The article also notes that the average household spends about $11.00 of electricity on the microwave per year which means that it’s probably not worth worrying about.
I did this experiment a couple of months ago. Anecdotal, yes, but what the hey.
I boiled 3 cups of water in a kettle on my gas stove and in my microwave (don’t know the wattage, but it’s new).
The kettle won by about a minute. However, I still use the microwave because I don’t want to have to drop everything and run to the stove because the kettle is screaming. Also, superheating isn’t a problem if you use something that’s not perfectly smooth (I use a Pyrex measuring cup), or you put a chopstick or wooden skewer in it.
When I just want a cup of something, I use the Sunbeam Hot Shot Water Dispenser. I suspect it’s more efficient than a standard large electric kettle. It heats much faster than the microwave as well (which may imply efficiency but I’m no expert)…
(My bolding)
You mean that you actually use a stove-top kettle? Is that standard practise in the US?
Over on this side of the pond I haven’t actually seen anyone use a stove-top kettle outside camping. When people talk about ‘kettles’ it’s always the electrical variety.
On the other hand, it could be because we have beefier power supply in our kitchens. 230V*16A is pretty much standard, and most electrical kettles are around 2 - 2.2 kW (Except GorillaMans 3kW monster.) whereas in another thread it surfaced that most US electrical kettles are closer to 1kW.
At least one point where Europe is ahead of the US…
Yes, a stovetop kettle. I believe they’re more common than electric ones here in the US. I don’t see why electric is any better, you can’t wash them as thoroughly, can you?
Well, for efficiency in one sense, you can use something else’s waste heat - boil it on the engine of your car, say. My dad used to make baked potatoes by stuffing them between pipes in the boiler room of the ship when he was in the Navy. Not a fast boil, I imagine, but it’s already paid for.
Well, one of the reasons they can be better is they switch themselves off when they boil - no need to go running back to the stove when it’s ready. I think that having the heating element immersed in the water must be more efficient than placing the kettle on top of a hot element - not sure how much more though. You’re right though, it’s not easy to give them a good scrub!
I think that the main reason most Americans use a stovetop kettle is that we already have a stove, and a stovetop kettle is much simpler (and therefore cheaper) than a standalone model. It’s hard to justify a fancy appliance just for one purpose (we take tea much less seriously over here).
That said, in the office, we have a microwave, and someone still thought it worthwhile to bring in an electric kettle in addition. Then also, we have several non-Americans in the office, too.
