# How long to preheat oven?

This is a silly question, but my wife will turn on the oven to preheat while she prepares stuff, but sometimes it takes her 15 minutes to 45 minutes before she puts things into the oven.

Generally, how long does one need to preheat the oven before it's to the desired temp? I know that this can easily be solved with a thermometer, but we don't have one.

• Is your oven electric, gas or solid fuel? – Orbling Dec 10 '10 at 13:59
• When I read "preheat the oven for 10 minutes at 180 degrees", I preheat it for 2-3 minutes at 360 degrees. It's not like I'm following the rest of the recipe anyway... :P – Camilo Martin Aug 20 '14 at 0:57
• I just cleaned up the thread from answers saying "my oven takes X time to reach Y degrees". I would like to remind everybody that we don't take poll questions where each answer is a single data point on one's personal opinion/experience, so answers to this question are also expected to contain general (and substantiated) information, not a single data point. – rumtscho Sep 16 '20 at 7:47

This depends on a lot of things.

The idea of preheating is that you want to get all the surfaces inside your oven (walls, floor, door, racks) up to the desired cooking temperature. This makes for more even temperatures throughout the oven, and gives a little thermal mass so you don't lose ALL your heat when you open the door for a few seconds or put something cold in there.

Then there's the question of what you're putting in the oven. An aluminum sheet with a few room temperature cookies on it won't pull the temperature in the oven down like a 25 pound turkey that's 40F/5C inside. You want to be more careful to do a complete preheat if you're going to be soaking up a lot of your starting heat.

Our oven, which has a large baking stone in the bottom all the time, takes a while to get uniformly up to temperature, even after the oven says it's preheated, because the stone doesn't heat up as fast as the rest of the surfaces. It takes at least 20 minutes after the "I'm fully heated" beep before the stone is fully up to temp. We have problems with things baking poorly if we don't preheat for quite a while, but on the upside, if we put a cold roast in or open the door a lot, the temperature in the oven stays pretty high.

If your oven is lightweight, flimsy or drafty, it may be as hot as it's going to get the moment the preheat alert goes off.

45 minutes is probably a lot more preheat than you'll need in almost any case. In some cases even 15 minutes is more than you need. It really depends on your oven and what you're putting in.

• Absolutely correct. The preheat beeper goes off when the air has reached temp, and opening the door of the oven will kill that right away. The more thermal mass (baking stone, bricks, I've even seen a full clay oven liner(found it hearthkitchen.com)) you have the longer it takes to heat up, BUT, the less fluctuation in temperature as you put food into it. – Doug Johnson-Cookloose Dec 10 '10 at 4:53
• Add to that... consider the degree you need to maintain constant temperature. When baking bread, you don't want that initial drop in temp from improper preheating (so preheat longer). But if you're warming up yesterdays casserole, who cares? – Robert Cartaino Dec 10 '10 at 15:37
• Do you turn on the convection fan for preheating? Or do you turn it on when you put the food inside? Because my oven keeps turning off by itself when preheating, I think it might be the fan. – Shayan Nov 1 '19 at 9:33

Most ovens I have used take from 15 to 20 minutes to get to 180C (350F). Many ovens have an indicator light that glows while it is below temperature (i.e. when the elements are on) so just watch for that to go out, and your are at your desired temperature

The key thing is that most modern ovens are well insulated and will not use much energy once at temperature and with nothing else to heat up, so going a bit longer isn't a big energy waster

If you want to save energy have a queue of things to bake one after the other, as a significant amount of energy if used just getting the oven up to temperature. Electric ovens are from 3000 to 5000 Watts, so each warm up cycle uses approximately one kWh (assuming 15-20 min)

You might not want to trust your on-board thermostat. I recently got a new oven thermometer and checked the temperature after the oven beeped saying it had reached 350 degrees but the thermometer only read 250.

• My oven does the same thing as Dee's. I purchased a thermometer and when the preheating alert sounds the thermometer shows the oven 100 degrees less. – user45054 Apr 14 '16 at 21:44

What this really depends on is what the voltage is to your house and what the oven is designed for. If you are finding your oven is taking a long time to heat up you will probably find that you are getting a 208 volt service (common in North America), especially in multi family buildings. If the oven is designed for 220-240 - you will notice a significant slower heat up time. North American made products are typically designed to work with both volt supply types. My manual for my oven (Fisher&Paykel DCS - from New Zealand) reports the oven will heat to 225 C in 15 mins - it actually takes 39 minutes.... super annoying.