Are all means of heating equally efficient? [duplicate]

Question

In terms of cost of electricity, does it matter if I heat my room using a space heater, an open oven, a flood light, an ASIC? Assume no energy escapes the room, that the heat quickly becomes uniformly distributed, and ignore the fact that these produce heat at different rates. Consider only the amount of heat produced per unit of electricity.

Answer 1

The Method Matters

This is just a theoretical discussion, and is not based on actual research on all forms of producing heat, but from a conceptual standpoint alone. What you use to heat an area does matter. It has to do with efficiency. If you have infinite time, then no, it doesn't matter. I've yet to meet anyone with near-infinite time.

Every mentioned method of generating heat tries to speed up molecules, and as they bump around with other molecules, they make those go faster, and eventually every molecule in the room is going faster. You measure the mean speed of them and... your room temperature has gone up! So the things you need to make a room full of molecules go faster is to increase the collisions and the speed of collisions between molecules.

The number of and speed of collisions are important to heating a room. Various heaters toy with these quantities to maximize heating. Things which are bad at heating rooms are bad at one or both of these things.

Okay, why does the method matter?

It has to do with how much of that ambiguous unit of electricity goes into making molecules move faster, and how much of it is spent doing other things.

The Flood Light, for instance, is less efficient than other forms, because it's making light. More energy is going into making light than into making stuff speed up.

What about the space heater? Yes, it glows and provides some light, but most of the energy goes into heating the metal, not making photons. It's therefore more efficient at heating than making light.

What about an open oven? Well, an oven and a space heater generally heat by the same methods, but the oven only means to heat a small space, not a large one. Yes, ovens are meant to heat things up, but it does not take advantage of convection outside of the oven. You could leave the door open, but only a small amount of the zippy molecules actually get to collide with the air.

If you dismantled an oven, I bet those heating elements without the oven walls would heat a room just about as well as a space heater. Alternatively, breaking the oven so convection cooking is on while the door is open could work as well. It should work about the same as a space heater.

What about computer chips, ASIC or otherwise? Well, they can produce a lot of heat. After all, you're messing with the individual bits, many times per second. There are even videos of people using computer chips to cook eggs! I suppose you could heat things with it, but it's expensive and super labor-intensive to use processors to heat on a large scale. You may run into convection issues, like with the oven. Additionally, they can only heat so much until the processor is fried, which is not as hot as space heaters can get.

Rate of Heat Output Does Matter

The rate at which a device heats is the crux of this problem. Efficiency is the rate of heat energy out to electrical energy in. (Usually measured in a set time-period.) You don't want a low-efficiency heater, because (1) your energy going into the device isn't using most of it for heating and (2) you may be losing more heat (per unit of time) in your house/room than the device is making (per unit of time).

If you ignore efficiency, and a lot of other practical and good things which are best not ignored, you can get the same amount of heat from each one of these things. For instance, a light left on for a year may produce the same amount of heat energy as a space heater left on for a minute.

In short, you will not successfully heat rooms using these devices interchangeably in the real world. If you have copious amounts of time, then yes, it doesn't matter, and the hot room will eventually get hot.