Preheating the Oven: “The Recipe Says So” myth.

t_squared

In these days of astronomic rises in energy bills, I have an issue with pre-heating ovens.

I am appalled by the number of recipes and “how to cook” on bought food items that demand that you pre-heat the oven.

This is a complete and utter waste of energy.  Nothing is being cooked at this stage.

The average oven uses about 3,000 watts of electricity every hour (about 3 kilowatt hours).

Those 3,000 watts in one hour also emit as many emissions as burning 1kg of coal.

Common sense tells us that if we’re preheating the oven, that energy is just being wasted; it’s not cooking anything.

OK, some recipes do need a preheated oven, for example, baked goods with yeast.

But for basically everything else, preheating doesn’t really matter and remains a total waste of energy.

I have looked at this pre-heating issue online and time and time again, it is stated that pre-heating is, indeed, totally unnecessary

Up to 10% of the energy can be saved in the cooking/baking process.

Maybe a campaign to stop recipes and other cooking instructions to stop printing this unnecessary step.

A whole lot of expensive energy can be saved!

razord

Unless your oven takes an hour to heat up, it won't use 3kWh in an hour. It'll hit temperature after 10 minutes or so and then use a few watts until it needs to turn the heating elements back on. In my experience, my oven uses about 1kWh an hour.

cannugec5

My oven is very slow to get up to the required temperature compared to the one it replaced. 

If I followed your advice and put a chicken in a cold oven it would not be cooked after the required time. If I was silly and did not check it was cooked thoroughly I would risk food poisoning. 

For that reason, recipes need to be standardised for safety. The only way to remove the variables in oven temperatures are to start off at an equal point i.e. at the preheated temperature. 

I totally agree the preheating is wasteful, but it does take the guesswork out. 

El_Torro

I haven't looked into this at all but I imagine the reason that instructions say to pre-heat is because different ovens take different amounts of time to heat up. So if the instruction is saying that it takes 20 minutes to warm something up (when pre-heated) then telling you not to pre-heat means the person making the instructions doesn't know how long your particular oven will take to get to the right temperature. Of course it's all guess work anyway because 20 minutes in one oven might equate to 22 minutes or 18 minutes in another oven. 

If all you're doing is heating something up (not for example cooking raw meat) then I don't really see the point of pre-heating. You just need to check occasionally to see that the food is adequately cooked.

Brie

It's not a myth.  It's essential for some recipes that need a short very hot time to cook.  Yorkshire puddings are one.  Baked Alaska is another.  

But if you are planning on slow roasting ribs for 2+ hours or reheating a store bought lasagne then I agree - stick it in when you turn the oven on and when you're getting to the end of the cooking time turn the oven off as the heat will be retained for quite some time.  And when you're finished using the oven leave the door open to help heat the house.

Robin9

Doing a casserole for tea - will just switch it on .   

t_squared

razord said:

Unless your oven takes an hour to heat up, it won't use 3kWh in an hour. It'll hit temperature after 10 minutes or so and then use a few watts until it needs to turn the heating elements back on. In my experience, my oven uses about 1kWh an hour.

The fact remains that energy is being wasted during the preheat period.

Apodemus

There is also an issue with bacteria in food getting time to multiply in a warm temperature before they are slowly killed (or form spores) when the temperature gets too hot.  This gives time for release of bacterial toxins into the food, which can lead to food poison.

victor2

The oven's thermostat will kick in as soon as the temperature is reached, reducing the energy used. Cooking something from a cold oven will take longer than starting with a hot oven, and for some food will not give the desired result.
If you want to really see how much extra energy the preheating is using, read the meter before and after cooking the same food each way and compare the results, allowing of course for other appliances cutting in during the cooking process.

kingstreet

Pre-heat for five minutes or add five minutes to the cooking time.

Six of one, half dozen of the other...

Apodemus

kingstreet said:

Six of one, half dozen of the other...

...but only one of these is safe from a food hygiene point of view.