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Steven Skoczen

Sustainability Showdown: Microwave vs. Toaster Oven

The Dilemma

You've pulled some leftover mac n' cheese out from the refrigerator, glance over at your counter, and see a microwave and a toaster oven. Which do you toss your plate of pasta into, if you're looking to be the most sustainable?

The Answer

The biggest sustainability concern in this case is energy usage, and the microwave wins out handily over the toaster oven. The best news is that you can easily verify this in your own home. Most microwaves and toaster ovens have the wattage they use printed directly on them. That number is pretty close to the actual power each device pulls. So, if you have an 1200W toaster oven and a 600W microwave, your microwave is generally using about half of the power of your toaster oven.

On average in the US, microwaves use 925 Watts, while toaster ovens average 1225W. So, on the surface, microwaves use about 20% less power than toaster ovens. However, microwaves also typically require less cooking time, leading to more significant savings. According to a 2006 study by the UK's Market Transformation Programme, microwaves used about half the power of toaster oven for similar tasks.

We've run some numbers for a few common meals, assuming you have an average microwave and toaster oven. Our cook times are based on either the packaging, or the exclusive expertise of Steven's mom. Other folks have found similar numbers.

But, as always, there's more to the story than that. That's why we have the fine print!

The Fine Print

Just how do microwaves get away with cooking faster, with less energy?
It seems like cheating, but it's true. The biggest difference is the types of radiation that each uses to cook food. Toaster ovens use infrared radiation, or heat coming off those glowing heating elements. While this does a good job of heating the food, it also heats the air in the oven, the toaster oven itself, and the room around it. Anyone who has touched the top of a just-used toaster oven can attest to that fact!

In contrast, microwaves work by using microwave" title="Microwave">microwave -">microwave" target="_blank">Microwave">microwave radiation to heat" title="Dielectric heating">heat -">heat" target="_blank">Dielectric heating">heat the molecules of just the food and container placed inside. This saves a tremendous amount of energy from being wasted heating the appliance, and surrounding room.

It's also important to note that microwave and infrared radiation have nothing to do with nuclear radiation, which can be dangerous. When your microwave and toaster ovens are off, they produce no radiation at all. Microwaves produce their electromagnetic radiation in much the same way as a fan turns electricity into the movement of its blades - there is nothing inherently dangerous happening!

What about disposal, when the appliances no longer work?
From what we could find, both microwaves and toaster ovens are 100% recyclable when disposed of properly. Both appliances break down into various metals, plastics and glass that can be fairly easily reused. Check out Earth 911's great recycling guides for where you can recycle yours. In terms of creation, microwaves look to be a bit more intensive to make, but that difference is more than offset by savings in usage.

Surely you don't mean to suggest I should make toast in the microwave.
Surely not. If you want a crisp crust of any kind, you'll need to expose your food to infrared radiation, like that from a toaster or pan. But for everything else, your microwave's likely an option, and could save you some energy!

Microwaves are often thought of simply for reheating, but can also be used to prepare food, including everything from rice to hard-boiled eggs, and a whole lot more.

Tips for saving more energy

There are a few other ways to save a significant amount of energy when using either or both appliances.

Power Strip
Place both your microwave and your toaster oven on a power strip, preferably one that you'll notice is on! Since many more advanced versions of each include electronic clocks, timers, and circuits, they pull power all the time, even when you're asleep and there's nothing to cook. Putting all your devices on power strips is a great way to stop that waste of electricity, and on average, saves about 10% of the power you microwave or toaster oven uses over its life.

This one's not immediately obvious, but makes a lot of sense. For larger frozen items, defrosting first can save as much as half the cook time - adding up to a whole lot of energy saved! The chart below shows the energy usage for baking a large frozen lasagna, frozen and defrosted.

Combine Microwaves and Toaster Ovens
This is a particularly effective way to cook, and get the best of both worlds. You can heat your meal mostly in the microwave, then transfer it to a toaster oven for the last minute or so, to get the crisp crust, potato skin, or tortilla that your taste buds request. If you've got both appliances, it doesn't have to be one or the other. Be creative, and try out new ideas!

The Verdict

The Microwave

For tasks that can be done in either the microwave or the toaster oven, the microwave wins out, hands down, in energy usage.

That's this week's showdown! Toss us your comments below, and if you have ideas for a future showdown, let us know!
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Sam Fladung July 19, 2009
I agree with your conclusions, but I'm not sure I believe that the printed wattages are pretty close to the actual power each device pulls

The power usage will usually be the maximum power drawn under operating conditions and not the average power draw (which varies based off of how the device is used). In making these calculations you can't use the simple energy= power * time but rather have to use energy= integral of power with respect to time.

To think about why you can't just use the number listed, consider a microwave with several power settings. It will not draw as much power on low as on high unless it is incredibly poorly designed. Yet the net energy usage would probably be approximately the same. A more efficient appliance may have a higher power rating simply because during a portion of its cycle it heats faster while using less energy overall.

If you consider an oven setup, it will dump a lot of power into the system to get it up to temperature. Once it reaches the desired temperature it will reduce the amount of power used to only that is needed to maintain the temperature. So the energy usage looks something like (energy to heat up the oven) + (energy needed to heat the food) + integral(heat loss rate) with respect to time.

The big advantage of the microwave is that it doesn't need to heat up the inside of the system since the heat is generated directly inside the food. Since most things you would consider microwave or toaster oven are relatively short term, the microwave wins big.

Also, does a dumb (no digital electronics) toaster oven outperform a microwave if you take parasitic into account? Ie, if you leave the microwave plugged in for a year does the power drawn by its clock and other circuits eat your savings?
Micaela July 21, 2009
You know what's even more green? Baking cookies in your car on a hot day:

I may have to try that this weekend and get something out of this horrible weather.
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