On a recent episode of Justin, Travis,
and Griffin McElroy's terrific advice podcast,
My Brother, My Brother and Me, the brothers pondered a Yahoo
Answers question about what would happen if you put a toaster inside
a freezer. (The discussion comes around the 36-minute mark.)
They have a fun discussion of a few aspects of the problem
before eventually moving on to the next question.
Since they don't really settle on a final answer,
I thought we could help them out by taking a closer
look at the physics of freezer toasters.
(A quick safety note: If you actually do this,
keep in mind that the toaster may melt some of the
ice in the freezer, leaving you with a running
electrical appliance in a pool of water.)
Griffin sums up the situation like this:
You put a toaster in a freezer. You run the extension
cord in there. You put some good bread in there.
You click it down. What even happens, right?
Because if your answer is, "it would get hot,"
then the freezer hasn't done its job.
But if you say "it would get cold,"
then the toaster hasn't done its job.
For starters, the answer: The toaster would win.
The freezer wouldn't do its job. Toasters beat freezers.
It's easy to think of a toaster and freezer as equivalent—
one cools things down and the other warms them up.
But toasters heat things up a lot more than freezers cool them down.
The coils in regular toasters get hot enough to glow,
which means they're over about 600°C.
Since the toaster is operating at such high temperatures,
it would hardly notice whether the surrounding environment is
20°C (room temperature), 4°C (a fridge), or -15°C (a freezer).
The toaster needs to heat its coils from room temperature
to somewhere over 600°C. From the toaster's point of view,
a 20- or 40-degree change in starting temperature hardly matters.
The coils will get hot, and then the bread will get hot, too.
If the bread is colder at the start, the toaster will have to heat
it a little longer to get it up to ideal toasting temperature,
but it will have no trouble getting there.
As anyone who's ever burned a piece of toast knows,
toasters are definitely capable of heating bread to
above the ideal temperature for toast.
In their discussion, the McElroys brought up another question:
Even if the toaster can still toast bread at first,
would it struggle to stay warm over time?
If you left both the toaster and the freezer running,
who would win in the long term?
The answer is that the toaster would still win.
A toaster produces about a thousand watts of heat,
and the cooling system in a household freezer can't
remove heat that fast. In fact, since freezers are so well insulated,
the inside of the freezer would probably get much hotter than the rest
of the house, and eventually the toaster and/or the freezer would probably overheat.
Refrigerators and freezers work by soaking up heat from their
interior and dumping it out the back. In a sense,
they're more efficient than toasters.
Fridges have a "coefficient of performance" of 2 or 3,
which means it only takes them 1 unit of electrical energy
to move 2 or 3 units of heat energy from the interior
to the exterior. A toaster, on the other hand, produces
1 unit of heat from 1 unit of electricity. But since the
compressor in a fridge-freezer typically only uses 100 or
150 watts when it's running,[4] so even with the efficiency
multiplier, it can't keep up with the
toaster's 1000+ watts of heat production.
Eventually, the toaster will start to heat up the
inside of the freezer. Even if the freezer were as powerful as the toaster,
it wouldn't be able to keep the toaster coils themselves from
getting hot and toasting bread. The freezer can make the air
around the toaster cold, but remember, to the toaster, all our air is cold.