# 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:** 8\ **Page:** 3
**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 11, 2021, 5:52am UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/41 "2021-09-11T05:52:05Z")
I happened to need to use the oven yesterday, and with this thread in mind, I actually timed it. It took 14 minutes to reach 350F. That’s quite a bit slower than my superfast previous oven, but still acceptable. And that’s with a covered lower element and a heavy pizza stone on the lower rack. I keep the pizza stone in there mainly for convenience, but it may actually be beneficial in helping to maintain a more uniform oven temperature. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [September 11, 2021, 6:19am UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/42 "2021-09-11T06:19:05Z")
One point about apparent efficiency. The energy dissipated in the element has to go somewhere. You can’t have an element coupling less than its input to the oven without the element itself continuously rising temperature and eventually melting or otherwise failing. Assuming it doesn’t fail, at an intermediate temperature it’s surface temperature rises to the point where improved convection and increased radiation carries enough energy away for the element to reach a steady temperature. Radiant heat directly heats the oven walls (or grills the food in the oven). Fans clearly improve transport, acting as a surrogate for convective motion. The balance between radiant transfer and convection changes, but you can’t have a situation where the energy is just vanishing from the system. If there is a couple of kilowatts going in as electrical energy, it’s is appearing in the oven in some form. Slow heating for a given power input can only be due to thermal mass of the oven or losses to the outside world. Usually conductive transport to the walls is reduced as much as possible by mounting the elements proud of the walls. ---
**Author:** ![Honolulu\_Lulu](https://avatars.discourse-cdn.com/v4/letter/h/87869e/32.png) [@Honolulu\_Lulu](https://boards.straightdope.com/u/Honolulu_Lulu)\ **Post date:** [September 11, 2021, 11:25am UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/43 "2021-09-11T11:25:20Z")
> [@engineer\_comp\_geek](#): > > The limit mainly comes from the standard electrical service for your home. > > 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. … That makes sense, but… I have two near-identical electric stoves purchased separately 20 & 28 years ago. If I set the oven to 400, the heating element will come on for 90-105 seconds, then shut down for 25 seconds. This on/off cycle will repeat for 12 minutes until the oven reaches 400°f. None of the stove-top burners are on. The electric stoves my family had 50+ years ago did not have this on/off cycle. ---
**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 11, 2021, 9:28pm UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/44 "2021-09-11T21:28:19Z")
> [@wolfpup](#): > > And that’s with a covered lower element and a heavy pizza stone on the lower rack. I keep the pizza stone in there mainly for convenience, but it may actually be beneficial in helping to maintain a more uniform oven temperature. The stone (and any other added mass) will slow the cycling between min/max temperatures, but it’s the design of the thermostat that determines what those min/max temperatures will be. > [@Francis\_Vaughan](#): > > Fans clearly improve transport, acting as a surrogate for convective motion. Nitpick: fans aren’t a surrogate for convective motion, the _enhance_ convective motion; it’s just that it’s forced convection rather than buoyant convection. ---
**Author:** ![Dr\_Paprika](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr_paprika/32/3042_2.png) [@Dr\_Paprika](https://boards.straightdope.com/u/Dr_Paprika)\ **Post date:** [September 12, 2021, 1:00am UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/45 "2021-09-12T01:00:37Z")
The question was answered by considering electric capacities. But the solution is to use an air fryer toaster oven with a big fan. I am amazed at how quickly it heats up, and it can be used for many things up to the size of a roast or chicken. ---
**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\ **Post date:** [September 12, 2021, 2:13am UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/46 "2021-09-12T02:13:34Z")
> [@puzzlegal](#): > > The inside of an electric oven could be air-tight Mine isn’t. That’s why it takes so long to heat up. I’m thinking of replacing the seals. ---
**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\ **Post date:** [September 12, 2021, 2:15am UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/47 "2021-09-12T02:15:58Z")
> [@Machine\_Elf](#): > > Nitpick: fans aren’t a surrogate for convective motion, the _enhance_ convective motion; it’s just that it’s forced convection rather than buoyant convection. Only because the industry decided to call fan-forced ovens ‘convective’. It’s used to distinguish between ‘convective’ and ‘radiant’ heating, but it’s confusing to anyone with an older technical education, because fan-forced heating _isn’t_ “driven by the density difference of heated and unheated fluid”. ---
**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 12, 2021, 8:05pm UTC](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371/48 "2021-09-12T20:05:02Z")
> [@Melbourne](#): > > Only because the industry decided to call fan-forced ovens ‘convective’. It’s used to distinguish between ‘convective’ and ‘radiant’ heating, but it’s confusing to anyone with an older technical education, because fan-forced heating _isn’t_ “driven by the density difference of heated and unheated fluid”. There are various kinds of convection, including forced convection: > **[Forced convection](https://en.wikipedia.org/wiki/Forced_convection)** > > Forced convection is a mechanism, or type of transport, in which fluid motion is generated by an external source (like a pump, fan, suction device, etc.). Alongside natural convection, thermal radiation, and thermal conduction it is one of the methods of heat transfer and allows significant amounts of heat energy to be transported very efficiently. > This mechanism is found very commonly in everyday life, including central heating, air conditioning, steam turbines, and in many other machines. Forc... An oven that utilizes forced convection can rightly be called a convection oven. [Previous page](https://boards.straightdope.com/t/why-do-ovens-take-so-long-to-warm-up/950371.md?page=2)