How much electricity to maintain an oven at 150 degrees?

[swee'pea99]

Surprisingly difficult (indeed thus far, for me, impossible) to get a straight answer to a simple question by googling.

Most sites seem to simply post a 'multiply the wattage of your appliance by the number of hours' solution, which strikes me as intuitively inapplicable to an oven. If you use a 1kw bar fire for an hour, that's 1kw. Fine. But an oven, I would imagine, only operates at its full rating while it's coming up to temperature, then uses a lot less to maintain that temperature.

It's not a big deal - I very much doubt the answer is going to dissuade me from slow-roasting my pork for seven hours - I'm just curious, and wondered if, in typical CC-stylie, someone out there might know the answer.

 

[welsh dragon]

No idea and as you say, not simple answer. It also depends on how long you want to maintain that temp for. Unless there is a specific need to know the answer, i'd just forget it. Sounds too much like a waste of time to me for no gain whatsover

 

[winjim]

You could take an empirical appriach. Assume the oven's either on at full power or off, depending on the state of the thermostat so you could sit with a stopwatch and time it. Start the clock when the light goes on, stop it when the light goes off. Monitor for the length of a slow cook. Multiply time by power.

This does give me another chance to mention my favourite unit, kWh/year. It has three time dimensions.

 

[presta]

Most sites seem to simply post a 'multiply the wattage of your appliance by the number of hours' solution, which strikes me as intuitively inapplicable to an oven. If you use a 1kw bar fire for an hour, that's 1kw. Fine. But an oven, I would imagine, only operates at its full rating while it's coming up to temperature, then uses a lot less to maintain that temperature.

You are right, they're wrong. The calculation you're being offered is based on the assumption that the element is powered continuously, but the oven has a thermostat which starts to cycle on and off once the set temperature is reached, at which time the mean power is equal to the element rating multiplied by the duty cycle of the stat.

The other mistake is that the rating on the plate at the back of the cooker is the total cooker power, and not the power of just the oven. There are various ways of finding the element rating depending on your confidence level, and how much trouble you want to go to. One is to look up the spare parts on a suppliers website (eg: Espares), another is to open up the cooker and measure the element resistance with a multimeter, and another is to use your electricity meter. In the latter case you would need to switch the whole house off except for the oven, and measure the consumption from cold, before the stat starts to cycle. (If you're looking up spare elements, bear in mind there will be more than one of them in the cooker.)

If you can find the element rating you can measure the duty cycle of the stat yourself. Presumably your cooker has an indicator light that goes on and off as the stat cycles, so all you need to do is time how long the light is on and off for once the oven is warmed up.

If Tf is the off time, Tn is the on time, and Pe is the power of the element, then the mean power Pm is:

Pm = Pe.Tn/(Tn+Tf)

Multiply that by the time your dinner takes to cook and the unit price, and you'll have the cost.

The mean power used by the element is equal to the power lost from the oven cabinet through the insulation of course, so an alternative, more theoretical approach, would be to calculate an estimate using the oven dimensions and the thermal resistance of typical insulation materials. If you were to do it both ways, you could compare the two, and see the accuracy of your calculations.

 

[sight-pin]

A smart meter would be able to tell you.

 

[Beebo]

A smart meter would be able to tell you.

My smart meter shows the oven uses quite a bit of power to get up to temperature, but once there the usage drops down.

I cant give you figures, because i would have to turn everything else off in the house, to have an accurate reading and my wife and kids would get cross.

 

[CanucksTraveller]

One point twenty one gigawatts.

 

[sight-pin]

My smart meter shows the oven uses quite a bit of power to get up to temperature, but once there the usage drops down.

I cant give you figures, because i would have to turn everything else off in the house, to have an accurate reading and my wife and kids would get cross.

But as soon as the oven calls for heat the meter will show a rise from, example 8p an hour too 29p, therefore if you stand watching the meter whilst your cooking the Sunday roast you can note down the difference every time the thermostat cuts in and add it all at the end. Oh! and don't let the kids turn anything on or off during

 

[classic33]

A smart meter would be able to tell you.

Only if nothing else was using electric at the time, or you already knew how much each appliance used.

 

[classic33]

My smart meter shows the oven uses quite a bit of power to get up to temperature, but once there the usage drops down.

I cant give you figures, because i would have to turn everything else off in the house, to have an accurate reading and my wife and kids would get cross.

Can depend on the age of the cooker as well.

 

[sight-pin]

Only if nothing else was using electric at the time, or you already knew how much each appliance used.

Can depend on the age of the cooker as well.

Now your just complicating things.

 

[classic33]

Now your just complicating things.

Beats letting the food being burnt because you were watching a smart meter, not the food.

 

[sight-pin]

lol

 

[sight-pin]

With that I'm gonna go and clean my bike. AFK.

 

[classic33]

With that I'm gonna go and clean my bike. AFK.

Don't forget the monitor

Ovens Above