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Are all electronical devices equally efficient at heat production?

S

Staples

Diamond Member
There is the old joke that you do not want to run your computer 24 hours because it wastes electricity and produces a lot of heat. This is very true and I agree with it however when it is cold outside, will a 300w electrical space heater create the same amount of heat as high powered computer which is eating 300w of electricity?

The computer is doing a lot more but I'd assume it creates exactly the same amount of heat.
 
Colt45 said:
Absolutely.

except its usually a 1500W space heater and a 150w computer.
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ditto. a PC does convert some energy to non-thermal energy, like sound/light, but that is a miniscule amount, and even much of that would eventually be converted to heat.
 
If the computer is drawing 300W then yes it is generating 300W of heat.

However if you have a 300W supply you'd better not be drawing 300W or your supply will probably fail.
 
No.

Some of the energy in the computer goes towards doing what it is that your computer does, while most of is given off as heat. So for 300W, some of 300J of energy is used by computer to do computer things (do work on its components) while most of the 300J is released as heat every second.

Nearly all of the energy in the heater is given off as heat. For 300W, nearly all of the 300J of energy is released as heat every second.

A heater is about as efficient as you can get.
 
PieIsAwesome said:
No.

Some of the energy in the computer goes towards doing what it is that your computer does, while most of is given off as heat. So for 300W, some of 300J of energy is used by computer to do computer things (do work on its components) while most of the 300J is released as heat every second.

Nearly all of the energy in the heater is given off as heat. For 300W, nearly all of the 300J of energy is released as heat every second.

A heater is about as efficient as you can get.
Click to expand...

The only energy output from a computer other than heat is light and sound. Light gets re-absorbed by whatever it strikes, turning back into heat. Sound also gets absorbed and turns back into heat. Everything turns back to heat eventually, it's the entropic way.
 
PieIsAwesome said:
No.

Some of the energy in the computer goes towards doing what it is that your computer does, while most of is given off as heat. So for 300W, some of 300J of energy is used by computer to do computer things (do work on its components) while most of the 300J is released as heat every second.

Nearly all of the energy in the heater is given off as heat. For 300W, nearly all of the 300J of energy is released as heat every second.

A heater is about as efficient as you can get.
Click to expand...

The 'work' a computer does doesn't count toward the normal work = force * distance definition. Nearly all electrical energy is radiated away as heat at some point, we just happen to get it to flip some switches along the way. (which ultimately generate heat, since they don't really move anywhere, at least not permanently, maybe writing flash memory might generate noticeably less heat than energy used?)
 
PieIsAwesome said:
No.

Some of the energy in the computer goes towards doing what it is that your computer does, while most of is given off as heat. So for 300W, some of 300J of energy is used by computer to do computer things (do work on its components) while most of the 300J is released as heat every second.

Nearly all of the energy in the heater is given off as heat. For 300W, nearly all of the 300J of energy is released as heat every second.

A heater is about as efficient as you can get.
Click to expand...

what do you suppose this "work" is? while I agree theoretically it's possible for components in a PC to undergo state changes as to permanently store some of the supplied energy as potential energy, they are not batteries after all; so such effects, if they exist at all, are quite limited.

light and sound production are more significant, and some of that can leak outside e.g. some of the light can escape through your window but it's all pretty negligible.
 
space heaters are a huge freaking drain on energy, they frequently use anywhere from 1500W - 3000W which is like a giant rooom of LAN noobs
 
I raised the question because I do not really rush to putting the PC to sleep every time I leave the room while it is cold outside because I have always figured it is either that or a space heater (which does nothing else but releases heat).
 
Staples said:
I raised the question because I do not really rush to putting the PC to sleep every time I leave the room while it is cold outside because I have always figured it is either that or a space heater (which does nothing else but releases heat).
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the heat created from your PC is negligible, turn it off and save $ instead

It just sits there sucking in dust, which is bad
 
running computers is not really as expensive as people think. I have 3 servers in my basement + my workstation on all the time. Among other things I have a small heater I keep under my desk so I don't have to heat the whole house if I'm in the office, and typical household stuff like a fridge etc...

Hydro bill this month was 50 bucks.
 
AC or DC

read about power factor for AC, inductive, capacitive and resistive loads , if your goal is to produce heat, you want a purely resistive circuit
 
PieIsAwesome said:
No.

Some of the energy in the computer goes towards doing what it is that your computer does, while most of is given off as heat. So for 300W, some of 300J of energy is used by computer to do computer things (do work on its components) while most of the 300J is released as heat every second.

Nearly all of the energy in the heater is given off as heat. For 300W, nearly all of the 300J of energy is released as heat every second.

A heater is about as efficient as you can get.
Click to expand...

Somebody didn't do so well in high school science class.
 
Well, some of the energy does goes into producing useful work, such as creating light, or crunching numbers, but ultimately, you're still putting 300W of energy into the system that is comprised of your house.


waffleironhead said:
There is a guy in the DC forums who heats his house with PC's. When it gets colder out, he just plugs in some more.
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One small office at work has no direct heat vents; it is heated mainly by the 5 computers and 3 people that are usually in there.

And I've got a dual dual-core Xeon system; I could always fire up Prime95 to help warm things up. 😀
(Incidentally, Prime95 makes full use of a quad-core system. Pro/ENGINEER Wildfire 4.0, expensive CAD software, can't. I max out at 25% CPU usage.)
 
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PieIsAwesome said:
Ack, lot of replies, but generally:

I don't mean mechanical work (though some of it occurs, ie fans), but electrical work. Some of the energy needs to be spend to do electrical work otherwise your PC would not do anything other than release heat.

See here:
http://www.articleworld.org/index.php/Electrical_work
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electrical work is an intermediate step. the PC doesn't output electircal energy nor is it stored in a significant quantity. it moves current in the PC but ultimately goes to either resistive loss or conversion to useful work like light.
 
PieIsAwesome said:
Ack, lot of replies, but generally:

I don't mean mechanical work (though some of it occurs, ie fans), but electrical work. Some of the energy needs to be spend to do electrical work otherwise your PC would not do anything other than release heat.

See here:
http://www.articleworld.org/index.php/Electrical_work
Click to expand...

Um, wrong. The actual processing parts of the computer basically solve logic. It just routes a signal through different gates, no real work is done like you're describing. The only output current or lack of current (basically 1s and 0s). There's no magical work going on. The actual power consumption is from the resistance to the flow of the electricity as it's routed through the different gates. All the power consumption from resistance to the flow of electricity is converted directly into heat.
 
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