Does leaving a pizza stone in the oven make the oven more or less efficient?

March 23, 2007 4:24 PM

Does leaving a pizza stone in the oven make the oven more or less efficient?

What effect might leaving my pizza stone in the bottom of my (electric) oven have on my cooking? On the energy/heating efficiency of the oven?

posted by chefscotticus to food & drink (15 answers total)

According to Alton Brown the temperature fluctuates as it cycles on and off. Using a stone will keep the temperature consistent.

Also Mr Brown reccomends using plain old bricks instead of a pizza stone cause it's cheaper.
posted by 4Lnqvv at 4:30 PM on March 23, 2007

Seconding 4Lnqvv's assertion, but when buying and using bricks or tiles, please make sure they are not treated with any coatings or backings or anything that might release toxins when exposed to high heat.
posted by Dizzy at 4:38 PM on March 23, 2007

IANAchef/physicist, but two things:

A) I would guess that the extra time the oven has to work to heat up the interior is mitigated by the fewer times it has to "kick on" during the cooking process.

B) I heart Alton Brown, but I would be careful about what kind of bricks you end up using; some are heat resistant, other can explode due to trapped moisture.

Please let us know how this works out - my oven is mostly used for pizza anyway, so I may try it myself...
posted by Aquaman at 4:42 PM on March 23, 2007

Used to use unglazed clay quarry tiles for this in an electric oven. Worked wonderfully.
posted by FlamingBore at 4:54 PM on March 23, 2007

It takes my oven longer to reach temperature when the stone is in it.
posted by rachelpapers at 5:07 PM on March 23, 2007

I used to leave our stone in the oven, but the pizza leavings (bits of cheese, cornmeal, etc) would burn up and cause a smell my wife found objectionable.
posted by DU at 5:17 PM on March 23, 2007

For strict energy efficiency, preheating time will increase. with my stone, it takes about 30-40% longer to reach moderate temps from chilly (350-450). However, likely due to some law of thermodynamics I am not aware of, heating actually speeds up towards the top end (500+, y'know, the temps for a good pizza). The longer the oven's on, the more energy expended during the cooking process, thus the less efficient.

On the other hand, in terms of cooking efficiency, having the stone in there helps even out temperatures in uneven ovens. Even temperature means that you can resist flipping whatever you're cooking to ensure even cooking, which means you don't open the oven door as often, which, I suppose, translates into increased efficiency, as well as a better overall product. I doubt it would make up for the preheating power expenditure, but who knows.

FWIW, In my experience all conventional (meaning non-convection) electric ovens, no matter the quality/age, have cool spots.

For the 'brick' discussion, I recommend uncoated, untreated slate. I think chefscotticus already has one though.


happy baking!
posted by markovitch at 5:30 PM on March 23, 2007

What do you mean by efficiency? Are you asking if it'll be cheaper to cook with a thermal ballast in the oven?

You can answer a question like this several ways.

Our pizza stone instructions call for heating the oven to 500 for an hour BEFORE putting in the pizza. Then, to cook the pizza for 10 minutes or less. I have 1 hour and 10 minutes of 500 degrees for one pizza. A second pizza calls for 15 more minutes. The second I turn it off, oven energy consumption stops. (With a stone inside, it cools slowly, but I am already napping after the pizza by then.)

Before pizza stone (BPS), I cooked pizza at 425 degrees for 30 minutes, and it took ~20 minutes to warm up. Lower temp, lower time, different result. The two types of pizzas were different, so it's an apples to oranges comparison.

Answering your question this way, it's arbitrarily more economic and energy efficient to cook one pizza in the BPS manner. Cooking two, less so, perhaps. Three, you do the math and tell me.

As far as the general question of oven efficiency with/without thermal ballast, I recently had this discussion about full versus empty refrigerators. The initial energy cost is more to bring mass to a specific temp (either hot or cold) is greater, but once at temp, the entire affair is based on the thermal resistance from the inside of the container to the outside. It has NOTHING to do with the contents!

It is more STABLE in the presence of a thermal upset, but it is no more efficient or less efficient. This stability is reflected in the duty cycle of the thermal element (either heater or cooler), but the absolute energy consumption can ONLY be affected by the thermal resistance from the interior to the exterior of the box.

In this sense, any 'efficiency' differences are trivial.

Will a ballasted oven cook faster? Probably. The heated mass in the oven will assist in quickly returning the inside of the oven to the setpoint temperature after the door is closed. Is it faster than just cooking at 500 degrees? Probably, because the pizza is in intimate contact with a large thermal mass.

Should you generally leave the pizza stone in the oven for energy reasons? No.

Should you leave the stone there for storage? If you have no where else to put it!

I take mine out. Except for pizza.
posted by FauxScot at 5:31 PM on March 23, 2007 [3 favorites]

"I used to leave our stone in the oven, but the pizza leavings (bits of cheese, cornmeal, etc) would burn up and cause a smell my wife found objectionable."

You are supposed to scrape that stuff off, DU. We scrape our pizza stone after each use (not washing it -- just scraping with a straight edge thing that came with the stone) and there is never any smell whatsoever from the stone when left in the oven after.
posted by litlnemo at 5:52 PM on March 23, 2007

...the pizza leavings coupled with my shocking laziness...
posted by DU at 6:28 PM on March 23, 2007 [6 favorites]

If you leave an oven on all the time, the only thing that affects the running cost is how much heat escapes through the top, bottom, and sides of the oven. Your pizza stone is unlikely to change this. FauxScot pointed this out.

If you only use the oven occasionally, you will need to run the oven for slightly longer to heat up the pizza stone (instead of the equivalent volume of air) to the cooking temperature. Again, the stone is unlikely to affect how much energy the oven needs to use to maintain cooking temperature.

For fun, you could measure this. If you cook the same thing on two different days, and if you can easily notice the state of the thermostat in the oven, then just use a stopwatch to time how long the oven is actually on for.
posted by hAndrew at 8:09 PM on March 23, 2007

DU, you made me actually laugh aloud.

We like the consistent heat provided by the stone. It cooks Crescent rolls better (even though they're on a cookie sheet on said stone), so we just leave it in.
posted by disillusioned at 5:29 AM on March 24, 2007

It takes a certain amount of energy to bring a pizza stone from room temperature to 400 degrees. After you are done cooking, all that energy comes out of the stone and warms the room. To a first approximation, that's the amount of extra energy that the pizza stone causes you to use.

The presence of this radiant heat reservoir evens out the temperature fluctuations of the oven, as long as the stone isn't so big as to impair convection.
posted by ikkyu2 at 12:04 PM on March 24, 2007

Define efficient. If you mean energy efficiency, which is what I expect you mean, then the stone will decrease it as there is more thermal mass to heat to the set temperature each time the oven is used, just like ikkyu2 said. (An oven differes from a fridge as you don't keep it at operating temperature 24/7) If you mean how well will it cooks, the stone will improve the oven's performance on many foods.
posted by caddis at 12:23 PM on March 24, 2007

My electric oven cooks so poorly that we needed to put extra thermal mass in it just to get things to actually cook! We use terra cotta plant saucers in general, but it's even better when we've got the pizza stone in (although it does take a really long time to heat up). When we had no extra thermal mass, I would try to cook a cake and after an hour at 350, it would still be really, really gooey.
posted by leahwrenn at 1:54 PM on March 24, 2007