# Why do ovens take so long to warm up? **URL:** \ **Category:** Factual Questions\ **Created:** [September 9, 2021, 11:55am UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371 "2021-09-09T11:55:30Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![JohnGalt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johngalt/32/184_2.png) [@JohnGalt](https://boards.straightdope.com/u/JohnGalt)\ **Post date:** [September 10, 2021, 1:44am UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/21 "2021-09-10T01:44:07Z")
Our new oven was obnoxiously slow to come up to temperature, much slower than our old one. I thought maybe it was because it’s a convection oven, and the fan was making it slow(?) After a few years I finally noticed the button labeled “Quick Preheat”. Hmmm. Wow! it’s super quick. Not to imply the OP missed something so obvious… ---
**Author:** ![crowmanyclouds](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crowmanyclouds/32/19884_2.png) [@crowmanyclouds](https://boards.straightdope.com/u/crowmanyclouds)\ **Post date:** [September 10, 2021, 8:01am UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/22 "2021-09-10T08:01:22Z")
> [@puzzlegal](#): > > {…} It’s a gas oven, so it still needs to vent hot air (and get fresh air for the gas to burn) {…} IIUC no. If the stove-top doesn’t require venting or a special source of air then the oven doesn’t either. What gas ovens are unique in needing vented is the water vapor produced by combustion. ---
**Author:** ![puzzlegal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/puzzlegal/32/3827_2.png) [@puzzlegal](https://boards.straightdope.com/u/puzzlegal)\ **Post date:** [September 10, 2021, 8:37am UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/23 "2021-09-10T08:37:18Z")
I’m confused by this statement. The flames produced by the stove top have direct access to the air in the kitchen. They won’t run out of oxygen unless the whole kitchen runs low on oxygen. And the kitchen as a whole is pretty well ventilated. The inside of an electric oven could be air-tight. But a gas oven can’t, because the flames within the oven need a source of oxygen, too. ---
**Author:** ![crowmanyclouds](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crowmanyclouds/32/19884_2.png) [@crowmanyclouds](https://boards.straightdope.com/u/crowmanyclouds)\ **Post date:** [September 10, 2021, 9:26am UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/24 "2021-09-10T09:26:56Z")
Some more AIUI. If you made the oven door air tight then when over cooled the door wouldn’t open. IE, the door can open, so hot expanding air in it can escape. If it was an air tight seal then a cooled oven door would seal like a jar of home canned food. Something that kinda does happen to your freezer/fridge door. A quick Google strongly suggests that the reason ovens have gaskets at all is just to prevent heat from escaping. Home ovens are not built to prevent air infiltration. They are, sometimes poorly, built to keep heat in. ---
**Author:** ![psychonaut](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/psychonaut/32/4655_2.png) [@psychonaut](https://boards.straightdope.com/u/psychonaut)\ **Post date:** [September 10, 2021, 10:22am UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/25 "2021-09-10T10:22:50Z")
Yes, particularly if your stove is on the other side of the kitchen as your oven. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [September 10, 2021, 12:17pm UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/26 "2021-09-10T12:17:03Z")
> [@Machine\_Elf](#): > > Want a faster preheat? You’ll either need a more powerful element… Thanks for doing the math - those were some cool numbers. However, I doubt that a more powerful element is the answer, since the heat transfer is dominated by the slowest path (heat transfer through air). Also you can put in more power to an element but you cant let it go to a higher temperature (within limits) because the element materials have a max temp. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [September 10, 2021, 12:41pm UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/27 "2021-09-10T12:41:05Z")
> [@Alessan](#): > > You’re waiting for the air inside the oven to reach the desired temperature, and air is a very poor conductor of heat. Others have spoken. But you raise an interesting point, and there’s much more about this. If you’re waiting for a temperature change to propagate through some thick body of something, the time it takes for a temperature difference to exponentially decay is dominated by the radius of the body and the thermal diffusivity. Thermal diffusivity is thermal conductivity divided by volume specific heat (aka mass specific heat times density). Air’s thermal diffusivity is actually about the same as steel, actually typically a tad higher. If this is surprising, consider that the heat content of a volume of air is far far lower than the heat content of the same volume of steel; it happens these are in roughly the same ratio, so their diffusivities are about the same. Well, but the air is pretty free to move, and will stir itself because it grows less dense with higher temperature. At self-cleaning oven temperatures, it’s about half as dense. It’s also about twice as conductive. And its thermal diffusivity becomes about four times greater. What takes a pretty long time is for the air to conduct heat to steel oven parts or other solid or liquid things. The air conduction makes a casserole take a long time, even when radiation and advection get involved. ---
**Author:** ![puzzlegal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/puzzlegal/32/3827_2.png) [@puzzlegal](https://boards.straightdope.com/u/puzzlegal)\ **Post date:** [September 10, 2021, 12:56pm UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/28 "2021-09-10T12:56:48Z")
I grew up with an electric oven. And if something caught on fire in the broiler, we closed the door and it went out because, if it wasn’t completely air tight, there wasn’t much airflow. I now have a gas oven, and that doesn’t work, because the oven is ventilated to allow the gas to burn. And a burning steak will just keep merrily burning. We either toss salt on the fire, or use a fire extinguisher. (Either of which ruins the food.) ---
**Author:** ![Jackknifed\_Juggernaut](https://avatars.discourse-cdn.com/v4/letter/j/9de053/32.png) [@Jackknifed\_Juggernaut](https://boards.straightdope.com/u/Jackknifed_Juggernaut)\ **Post date:** [September 10, 2021, 1:13pm UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/29 "2021-09-10T13:13:01Z")
Ah, the heating of the walls and oven mass taking that long makes perfect sense. Sometimes I shut the oven off, open the door and remove the heated item, only to discover that the food isn’t warm enough. If I then turn the oven back on (say after 5 minutes), it doesn’t take nearly as long to get back to 400. This must be because the walls are still hot. ---
**Author:** ![crazyjoe](https://avatars.discourse-cdn.com/v4/letter/c/f14d63/32.png) [@crazyjoe](https://boards.straightdope.com/u/crazyjoe)\ **Post date:** [September 10, 2021, 1:21pm UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/30 "2021-09-10T13:21:18Z")
> [@am77494](#): > > > [@Machine\_Elf](#): > > > > Want a faster preheat? You’ll either need a more powerful element… > > Thanks for doing the math - those were some cool numbers. > > However, I doubt that a more powerful element is the answer, since the heat transfer is dominated by the slowest path (heat transfer through air). Also you can put in more power to an element but you cant let it go to a higher temperature (within limits) because the element materials have a max temp. “A more powerful element” would simply be one with a larger radiating surface, which would put more heat into the oven more quickly. To do this would require higher levels of current but not necessarily a higher temperature. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [September 10, 2021, 1:34pm UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/31 "2021-09-10T13:34:29Z")
> [@crazyjoe](#): > > A more powerful element” would simply be one with a larger radiating surface,… So you are saying that the surface area contacting the air is the limiting factor, currently ? Not saying I disagree, just want to understand what you are saying. ---
**Author:** ![crazyjoe](https://avatars.discourse-cdn.com/v4/letter/c/f14d63/32.png) [@crazyjoe](https://boards.straightdope.com/u/crazyjoe)\ **Post date:** [September 10, 2021, 1:45pm UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/32 "2021-09-10T13:45:21Z")
A larger heated [quote=“am77494, post:31, topic:950371, full:true”] > [@crazyjoe](#): > > A more powerful element” would simply be one with a larger radiating surface,… So you are saying that the surface area contacting the air is the limiting factor, currently ? Not saying I disagree, just want to understand what you are saying. [/quote] A larger amount of heated mass (ie a larger element) will increase the total energy input into the system, which will increate the rate at which heating takes place. ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [September 10, 2021, 2:31pm UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/33 "2021-09-10T14:31:17Z")
> [@puzzlegal](#): > > because the oven is ventilated to allow the gas to burn. Most gas oven designs that I have seen don’t just burn the gas into the oven, but rather into heating elements that are enclosed, having their own air supply and ventilation. I haven’t seen one that just has a burner _in_ the oven. > [@engineer\_comp\_geek](#): > > In the U.S., you typically have a 240 volt outlet (assuming that your kitchen is set up for an electric stove and not gas) which will be rated somewhere between 30 and 50 amps. Your stove has to be sized so that it won’t blow the breaker even if you have all four burners on plus both oven heating elements. If you put in more powerful heating elements so that your oven would heat up faster, you would blow your breaker. My kitchen, and every kitchen I’ve known much about, has the stove and the oven on separate breakers. > [@running\_coach](#): > > The mass of the oven itself has to come up to temp. Which is why my toaster oven, plugged into a normal wall outlet, heats up far faster than the oven in the wall. (Downside is I can’t use the microwave as well, without blowing the breaker.) ---
**Author:** ![Do\_Not\_Taunt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/do_not_taunt/32/2968_2.png) [@Do\_Not\_Taunt](https://boards.straightdope.com/u/Do_Not_Taunt)\ **Post date:** [September 10, 2021, 2:39pm UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/34 "2021-09-10T14:39:49Z")
> [@psychonaut](#): > > Yes, particularly if your stove is on the other side of the kitchen as your oven. Sure, why not? I was definitely thinking of a combined oven/range, like every place I’ve ever lived has and I have been led to believe is most common (in the US at least), but in an age where internet-connected appliances exist, there’s no reason why a separated oven and range couldn’t talk to each other. Of course, you’d only need this if they were on the same circuit anyway. Otherwise, the oven could just draw as much as it wants, up to the limits of its circuit. > [@k9bfriender](#): > > Most gas oven designs that I have seen don’t just burn the gas into the oven, but rather into heating elements that are enclosed, having their own air supply and ventilation. I haven’t seen one that just has a burner _in_ the oven. I’m pretty sure my gas oven’s burners are exposed to the same air supply as the food in the oven. Like someone mentioned upthread, I’ve understood this to cause a problem with humidity, despite it being vented. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [September 10, 2021, 2:49pm UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/35 "2021-09-10T14:49:01Z")
> [@crazyjoe](#): > > “A more powerful element” would simply be one with a larger radiating surface, which would put more heat into the oven more quickly. To do this would require higher levels of current but not necessarily a higher temperature. This. **[Oven heating elements have all sorts of geometries](https://www.google.com/search?q=oven+heating+element&sxsrf=AOaemvLw3VrZVM8RFyHlSbQCCrRG3nycvA:1631285114784&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjkuazO0vTyAhUUFVkFHRX4ALQQ_AUoAnoECAIQBA&biw=2009&bih=1543)**; it’s a simple matter to squiggle them back and forth across the floor of the oven to achieve the desired length (and therefore total surface area) so that you can heat the air quickly without overtemping the element. Incandescent light bulbs have a similar issue. the filament is actually **[a coiled coil](https://www.google.com/search?q=light+bulb+filament&tbm=isch&ved=2ahUKEwj2joHQ0vTyAhXVbqwKHVtJBQQQ2-cCegQIABAA&oq=light+bulb+filament&gs_lcp=CgNpbWcQAzIFCAAQgAQyBQgAEIAEMgUIABCABDIFCAAQgAQyBQgAEIAEMgUIABCABDIFCAAQgAQyBggAEAUQHjIGCAAQBRAeMgYIABAFEB46BwgjEO8DECc6CAgAELEDEIMBOggIABCABBCxAzoECAAQQzoHCAAQsQMQQzoLCAAQgAQQsQMQgwFQ6qUGWL2zBmCCtAZoAHAAeAKAAb8BiAGsDJIBBDE1LjOYAQCgAQGqAQtnd3Mtd2l6LWltZ8ABAQ&sclient=img&ei=fm87YfbXD9XdsQXbkpUg&bih=1543&biw=2009#imgrc=9FaA-AFUlbfhTM)**, giving it the total length you need to deliver the brightness you want without overtemping the filament, and without having to have a bulb that’s thirty feet long (i.e. with a simple linear filament). ---
**Author:** ![crazyjoe](https://avatars.discourse-cdn.com/v4/letter/c/f14d63/32.png) [@crazyjoe](https://boards.straightdope.com/u/crazyjoe)\ **Post date:** [September 10, 2021, 3:39pm UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/36 "2021-09-10T15:39:51Z")
> [@k9bfriender](#): > > My kitchen, and every kitchen I’ve known much about, has the stove and the oven on separate breakers. Depends on if you have them separate or not. Most kitchens in the USA use what we call a “Range” which is an oven and stovetop combined, and they only have one plug in the back (typically 240v) so it would be impossible for them to be on separate breakers. ---
**Author:** ![phs3](https://avatars.discourse-cdn.com/v4/letter/p/8491ac/32.png) [@phs3](https://boards.straightdope.com/u/phs3)\ **Post date:** [September 10, 2021, 3:44pm UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/37 "2021-09-10T15:44:44Z")
“Fast preheat” means “Use both top and bottom elements”. And yes, the enclose elements slow things down. Much like smoothtop cooktops, it’s style over function. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [September 10, 2021, 3:56pm UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/38 "2021-09-10T15:56:25Z")
On the subject of oven ventilation, electric ovens may or may not need less venting than gas ovens, depending on whether the gas is burned in its own separately vented compartment, but electric ovens do have venting. At least, all the electric stoves I can remember did. My old stove, with old-style coil burners, had a vent hole directly beneath one of them. The current one has a solid glass top, so the oven door itself has vent slots near the top. My guess is there are at least two reasons for this: to help create convection currents, and to exhaust the moisture from the cooking food. ---
**Author:** ![puzzlegal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/puzzlegal/32/3827_2.png) [@puzzlegal](https://boards.straightdope.com/u/puzzlegal)\ **Post date:** [September 10, 2021, 4:20pm UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/39 "2021-09-10T16:20:12Z")
> [@k9bfriender](#): > > > [@puzzlegal](#): > > > > because the oven is ventilated to allow the gas to burn. > > Most gas oven designs that I have seen don’t just burn the gas into the oven, but rather into heating elements that are enclosed, having their own air supply and ventilation. I haven’t seen one that just has a burner _in_ the oven. I have never seen such a thing. My not-incredibly-old GE gas oven has visible flames on the top when the broiler is on. I guess the bottom flames are underneath a piece of metal, but there are slots on either side of that piece of metal, so it effectively shares airspace with the rest of the oven. ---
**Author:** ![Snipe70e](https://avatars.discourse-cdn.com/v4/letter/s/51bf81/32.png) [@Snipe70e](https://boards.straightdope.com/u/Snipe70e)\ **Post date:** [September 11, 2021, 5:30am UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/40 "2021-09-11T05:30:05Z")
We replaced my wife’s double ovens. Cost was a factor. the new oven takes much longer to get up to temp. the new ovens have smaller heating elements. [Previous page](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371.md?page=1) [Next page](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371.md?page=3)