This may sound incredibly stupid, but this isn’t one of those hypothetical questions.
It’s starting to get fairly cold here and I’ve noticed that turning my oven on and leaving the door open heats my small apartment (around 650sqft I think, but I can’t remember the exact number) faster and warmer than the central heat.
Am I wasting energy and money doing this? If so, is it a considerable or negligible amount? If it’s not a huge difference, I think I actually prefer the oven heat.
If it’s a gas oven, don’t. The ventilation system isn’t designed for this, so you could end up with carbon monoxide building up. Then you could become very cold.
Assuming it’s an unvented gas oven, which is running clean (nice blue flame) you are getting about 100% efficency, If your using natural gas it’s about as cheap as you will get. It doesn’t mean you should as there are concerns about unvented combustion, but it is done quite often.
If you are using LP gas then it depends on the price per gal you are paying, but again the efficency is near 100%.
If you have an electric oven, then it is 100% efficent, but electricty is much more expensive (heat pumps are an exception).
It’s electrical; sorry I planned on mentioning that in my OP and then forgot.
In theory, the cost for heating should be exactly the same as an electric bar heat. However, since most kitchens are poorly insultated and typically far from the living areas, you are wasting heat. Instead of heating your room, you’re heating the kitchen, corridoor and that nasty draught in the kitchen (who doesn’t have one?).
Oh, and having an open oven is a nasty safety hazard.
Stick with a bar heater in your room and close the doors.
OK, my earlier disclaimer negated…my experience in a non-centrally-heated house is that the ‘short burst’ heating method, which you are taking to an extreme, seems very efficient. But you turn off the heat source, and it gets cold very quickly. That’s because the walls swallow up vast amounts of heat. With central heating, there’s a more gentle trickle, so you don’t notice the sudden blast of heat, but nor do you get a huge loss of heat from turning the source off. I’m pretty sure it’s all to do with perception - as kanicbird points out, although more expensive than gas, electric heating has a near-100% conversion, so there’s no way your money is somehow slipping away without you seeing the benefits at all.
What might help is to boil water on the stove. That way, the heat radiates for a long time. If you don’t pay for hot water (as most New York City dwellers don’t) you could fill up your bathtub and let heat radiate that way too.
But please, don’t use your oven to heat your house. The CO will kill you.
Err, what’s a bar heater?
And, to be honest, this is the Valley of the Sun. It’s not that cold :). I’m just trying to heat the kitchen and living room areas (which are attatched, without a hallway in between.) The bedroom is plenty warm with a comforter and a quilt, and we only go in there when it’s time to go to sleep anyway.
Not with Ciscos’ electric oven, it won’t.
My propane (gas) oven has done a great job of not killing me, as well, though I must admit that (a) my house is not exactly airtight and (b) I don’t leave it on when I go to bed, as I am afraid of fires (plus, I can’t count on the oven to shut itself down, as the oven’s thermostat doesn’t have a setting for “65 degrees farenheit in the bedroom, but don’t incinerate the cat, please.” 
My first apartment was a small one-room “efficiency”, with no AC or heating. I did have an oven, though- and was told by my landlord that it was my source of heat during the winter. It was unvented, and wasn’t even anchored to the floor- it was literally just sitting there, by itself, since I didn’t even have anything that could reasonably be called a kitchen. It had a pilot light, albeit one that was slow to ignite the gas; and since it wasn’t anchored in any way, the oven would ignite with a bang. That was always fun for guests. :eek:
I had no idea that CO was something to worry about, at the time… so it’s a miracle I’m still alive. Man, that landlord was a jerk.
It did keep the room nice and toasty, though.
Err, subsitute ‘electrical heater’ for ‘bar heater’ **Cisco **. 
The difference between an electric space heater and central air is not so much the speed, as the type of heating. Many electric heaters are radiant heaters designed to heat objects (such as people) in the room by direct infrared radiation. So you turn it on, WHAM! Heat rays warming you skin. But the air is still the same temperature. So when you turn the heat off… BRRRR instant cold. Leave the radiant heat on long enough and all the walls will be heated up and they will then eventually heat up the air. (Assuming the radiant heat source is large enough to overcome any heat loss from the room, which most small space heaters are not.)
Central heat is the opposite. It uses gas or electric to heat up the air and then blows hot air on you and you are warmed by convective heat transfer from the air to you. Much less instant. Since the central heat is on all the time and is usually sized large enough, the hot air eventually heats up the walls and floors so you don’t notice much when the unit cycles off and on.
So, the electric oven would work just fine to heat up the areas desired by the OP. It would be just as efficient as an electric space heater, and would be more efficient than using his central air system (if he has one) as it will only be on long enough to heat the people in the kitchen area while they need it and will not waste energy heating other parts of the house or for other periods of time. Since an electric oven is usually on a 240 volt 30 amp circuit here in the states, it will most certainly heat up the kitchen faster than a single electric space heater rated at 120 V 15A. And many kitchens will not be wired adequately to be able to run 2 or 3 space heaters in the kitchen while using all the other things you need electricty for in the kitchen.
But it’s still a bad idea. Nothing like leaving a large open door into a 400 degree space jus waiting for you to do something stupid. I’d have 2nd degree burns within a week of trying this. Or I’d burn the house down after dropping a napkin into the oven.
I’m wondering how clean the oven is as well. Nothing like 8 month-old burnt meatloaf smell wafting through the apartment for hours at a time all winter…
If you could just rig a self-cleaning oven to start the cycle with the door open, that’d take care of the eight month old meatloaf drips and get things really warm.
Errr… no. The clean cycle is in the neighborhood of 1000 degrees - and you thought leaving the oven door open at 350 was an invitation to a burn or other calamity?
Think about that for a minute or two. 
[OT]How do they not pay for hot water?
And what is this “CO” you speak of?[/end naive off-topic]
My comment, about suddenly losing heat when I turn off electric heaters, didn’t involve radiant heaters - I’ve got wall-mounted storage heaters and oil-filled radiators.
There are some radiant central heat systems and many convection space heaters, so it’s not so cut and dry. And even then a radiant heater has some convective heating, and to a lesser degree the reverse.
The basics are here though, radiant travels though the air as a light wave, and heats what it ‘shines on’. They usually glow red hot in electric space heaters and are pretty much instant. Gas and Kero space heaters also glow but take some time to get the radiant part up to tempature. Radiant heat can be used to heat a space outdoors as the heat ends up directly on the person.
Convective heating, both natural and fan forced, heats the air and that air heats the person. Electric space heaters of this type don’t normally glow and produce a warm stream of air. It is a bit slower then radiant, but then again electric space heaters are generally pretty fast. Gas and Kero space heaters get up to temp generally faster then radiant (as the radiant element is removing heat while it’s trying to warm up greater then convection can remove heat from a convection heater).
The oven’s element acts as a radiant electric heater (gas oven would be more convection), but much of that radiant heat lands on the interior of the oven, where some is converted to convection, while some is re-radiated.
As for efficency, it depends on what you consider efficency.
Energy into heat - Oven or elctric space heater wins at 100%, Vented Central Heat may be at 80%
Money into heat - Most likely an unvented gas or kero heater, then the central heating system (or electric heat pump), then electric heat system (not heat pump).
Getting heat fast - The more heat sources you can turn on at the same time the faster in general, unless you are taking warm air from one room and blowing it all over the house. Heat an small as a space as practical.