House Lights, Electric Heat, Winter, and Entropy

[passedpawn]

If you have electric heat, do you turn off your indoor lights in the winter? Seems you could leave them on all winter and not lose a penny on your electric bill.

Doesn't all the power into the lights end up as heat in your house? So, you get the light for free, and the electric heater just runs that much less to warm your house.

Of course, you have to disregard the cost of the bulbs, but I've switched over to mostly LEDs, and they seem to last forever.

 

[The_Bishop]

I would think you'd get *some* heat, but not much. Especially with LED bulbs. The idea with more efficient lighting is more of the watts get converted to lumens instead of heat.

 

[passedpawn]

I would think you'd get *some* heat, but not much. Especially with LED bulbs. The idea with more efficient lighting is more of the watts get converted to lumens instead of heat.

What do you think happens to light after it leaves the bulb? It turns to heat when it hits an object. Some of it might get reflected, but ultimately it all gets absorbed and turns into heat.

So, for a lamp, whether LED or incandescent or fluorescent, the rated wattage will all end up as heat.

 

[imasickboy]

Your heater is a much more efficient source of heat than your lights. Penny for penny, you'll get much more value out of your actual heater. Unless, of course, you want your lights on all the time, then there's no reason to ask the question in the first place.

 

[passedpawn]

Your heater is a much more efficient source of heat than your lights. Penny for penny, you'll get much more value out of your actual heater. Unless, of course, you want your lights on all the time, then there's no reason to ask the question in the first place.

But if 100% of the energy from my bulbs goes into heat, how can my heater compete with that kind of efficiency?

 

[imasickboy]

100% of the energy you put into the bulb doesn't turn to heat. A majority of it turns to light. The heat is a by-product, and any heat caused by the light itself is minimal, especially after the losses are considered.

 

[Sniderzj]

You're correct that incadesent bulbs are very ineffecient and most goes immediately to heat. Two problems....... One is the 60 watts per bulb times say 20 bulbs is 1800 watts...... About one hair drier so that's won't make a percepable difference in a 1000 sqft home. Second problem, most 90%+ , o the electricity heats the glass bulb but doesn't convect well from thre, that why the bulb will burn you if you touch it, but again not much use. It's simply ineffecient heat transfer to where you want it.

Side note to your point, I've heated fermentation chambers during the winter with a lamp and fan to maintain temp.

 

[Sniderzj]

Sorry 30 bulbs....

 

[Dfitz]

My light bulbs are the modern energy efficient LED type. Efficient lighting not heating

 

[passedpawn]

100% of the energy you put into the bulb doesn't turn to heat. A majority of it turns to light. The heat is a by-product, and any heat caused by the light itself is minimal, especially after the losses are considered.

Where does that light go then? Clearly, when you turn the light off, it's not still bouncing around the room - it gets dark. That energy must go somewhere. Energy is NEVER lost.

So, let's just say that all the light energy hits the wall and turns to heat. If that's true, then 100% of the bulb energy has ended up as heat. That's radiative heating. Is that a "thing"? How do you think the sun heats the earth?

 

[madscientist451]

If you have electric heat, do you turn off your indoor lights in the winter? Seems you could leave them on all winter and not lose a penny on your electric bill.

Well I could...but then my Lady Friend would have to look at my beer gut when she....you know....gets frisky....

 

[Jaybird]

The big question is can an LED bulb make a difference in a room with the energy it 1 consumes or 2 delivers. The answer is "probably" no.

The energy would end up being lost to atmospheric wasteland. Like trying to heat a large swimming pool with a aquarium heater. The losses are greater than the energy put into it.

Just a thought..

Cheers
Jay

 

[imasickboy]

Where does that light go then? Clearly, when you turn the light off, it's not still bouncing around the room - it gets dark. That energy must go somewhere. Energy is NEVER lost.

So, let's just say that all the light energy hits the wall and turns to heat. If that's true, then 100% of the bulb energy has ended up as heat. That's radiative heating. Is that a "thing"? How do you think the sun heats the earth?

Jay's bit about the swimming pool is a good example. It's not necessarily lost, but just of so little use, it'll never be measurable.

 

[Sniderzj]

Physics fellas - visable light is radiant energy and so is heat... So heat=light. Don't believe? Google "infrared". The OP has the issue of very low btu's and even lower htc's (heat transfer coefficient). An electric heater has high btu's and decent Htc's. By all means leave the lights on, but it's like a fart in a hurricane.

 

[passedpawn]

The big question is can an LED bulb make a difference in a room with the energy it 1 consumes or 2 delivers. The answer is "probably" no.

The energy would end up being lost to atmospheric wasteland. Like trying to heat a large swimming pool with a aquarium heater. The losses are greater than the energy put into it.

Just a thought..

Cheers
Jay

LED light bulb won't heat a room by itelf, I know that. But my point is that there are NO losses, so just leave it on. ALL of the energy put into it become heat, 100%. I keep saying this over and over and it doesn't seem to register.

When you say "lost to atmospheric wasteland", do you mean it will "heat my house"?

 

[Dimax]

Does this help at all I don't mean to but in at all'
Do LED lights give off heat?
In one sense this is true: LEDs are cool to the touch because they generally don't produce heat in the form of infrared (IR) radiation (unless of course they are IR LEDs). IR radiation heats the enclosures and surroundings of incandescent bulbs and other sources, making them hot to the touch.

 

[Zuljin]

Where does that light go then? Clearly, when you turn the light off, it's not still bouncing around the room - it gets dark. That energy must go somewhere. Energy is NEVER lost.

So, let's just say that all the light energy hits the wall and turns to heat. If that's true, then 100% of the bulb energy has ended up as heat. That's radiative heating. Is that a "thing"? How do you think the sun heats the earth?

It doesn't. The Earth is heated from the inside out by its molten core.

 

[Jaybird]

You keep saying it over and over, yes. But you have to understand what LOSSES also come from it and where that energy goes. I mean there are losses in the WIRE that feed the lamp buddy, but they are not going to make 1 little dent in the transition of energy into that lamp. Nor are they going to add heat enough to reduce the energy used in those losses. Is there heat yes. Will it overcome the cost per KW vs transferred energy into usable heat? I personally doubt it. But hey do some tests using a KW meter and a thermometer and be the man behind the breakthrough of every parent telling their kid to turn off that light!.... LOL
We did some tests years ago on an AC unit where we put the compressor in a temp controlled environment, blew cold air on it then we sprayed cold water on it etc etc. Want to take a few guesses as to what we found out as far as Energy used vs temp drop and efficiency of the compressor was? Not to derail your thread or anything....

Cheers
Jay

 

[passedpawn]

You keep saying it over and over, yes. But you have to understand what LOSSES also come from it and where that energy goes. I mean there are losses in the WIRE that feed the lamp buddy, but they are not going to make 1 little dent in the transition of energy into that lamp. Nor are they going to add heat enough to reduce the energy used in those losses. Is there heat yes. Will it overcome the cost per KW vs transferred energy into usable heat? I personally doubt it. But hey do some tests using a KW meter and a thermometer and be the man behind the breakthrough of every parent telling their kid to turn off that light!.... LOL
We did some tests years ago on an AC unit where we put the compressor in a temp controlled environment, blew cold air on it then we sprayed cold water on it etc etc. Want to take a few guesses as to what we found out as far as Energy used vs temp drop and efficiency of the compressor was? Not to derail your thread or anything....

Cheers
Jay

Sure, I'm interested in your experiment with the compressor. Derail away, I'm game.

 

[passedpawn]

It doesn't. The Earth is heated from the inside out by its molten core.

So, when I get a sunburn is that the molten core reflecting off the clouds

My question (and point) is that light heats surfaces through solar radiation.

 

[GreenMonti]

LED's do make heat. That's the number one killer of LED's. Led fixtures have to have adequate cooling or you'll never see the full life span. You my friend have read this I'm sure being a reef enthusiast. just not much heat (in a heating of a room sense) as you mentioned, energy conversion. They don't consume much energy therefore they don't produce much heat. Heat is the byproduct of the amount of work done, right? Your reef tank is radiating heat.

I get where your coming from though. It's energy used and it should translate straight across to the input of heat in the home. There's just so many factors that determine if it's a viable energy source. The amount of insulation in the home, how many air leaks, temp difference inside vs outside.....

 

[jleiii]

Physics fellas - visable light is radiant energy and so is heat... So heat=light. Don't believe? Google "infrared". The OP has the issue of very low btu's and even lower htc's (heat transfer coefficient). An electric heater has high btu's and decent Htc's. By all means leave the lights on, but it's like a fart in a hurricane.

'Light' is not heat. Infrared energy is heat and is a narrow spectrum at the red end of visible light, and beyond. Many forms of heat produce no visible light at all due to their longer wavelength.

 

[Horseflesh]

Light is not heat, but it does carry energy. The light emitted by a bulb definitely does turn into heat when those photons hit something. But, according to this a light bulb is about 2% efficient at turning electricity into light in the first place.

https://en.m.wikipedia.org/wiki/Luminous_efficacy

So, your 60W bulb is already a 58.8W electric heater and the energy carried by visible light is minuscule. You're spreading 1.2W of energy, in the form of light, all over the illuminated surfaces... so how much does the LIGHT from a bulb warm a room? Not much!

If you have LED lights the efficiency is much higher, around 10%, but the light consumes many fewer watts. So again, you end up with a couple of watts carried away as light and the rest turned into heat inside the LED, which radiates away.

What were we talking about? I'm getting a beer.

 

[Pkrd]

What were we talking about? I'm getting a beer.

When you grab that beer remember to leave the fridge door open. It will warm up your house.

 

[harrke]

Opening the fridge will warm your house. True!

Leaving lights on will heat your house. True!

The sun is the ultimate source of all the energy produced and used on this planet except nuclear. True!

Ok, reference for point number 2. New construction on a submarine in Groton Connecticut. In winter. We adjusted the temperature inside the hull by screwing 100W incandescent bulbs in and out of the string lights.

But…

A lot of the electricity used to light your house is flowing through wires that are not inside the insulated space that you want to warm up. So, even if you used all incandescent bulbs, you'd be losing some heat to that space outside the area you wanted hot. You do get heat from the lightbulb by leaving it on, but the amount of loss to outside would mean that it's not "free" heat. You'd be paying a little bit more than if you let your electric heater do its job.

 

[Pkrd]

The sun is the ultimate source of all the energy produced and used on this planet except nuclear. True!

Tell that to the dinosaurs.

 

[harrke]

Where did they get their food?

 

[harrke]

That's right, the sun supplied that energy!

 

[Zuljin]

So, when I get a sunburn is that the molten core reflecting off the clouds

My question (and point) is that light heats surfaces through solar radiation.

The term sunburn is a colloquialism. Our skin turns red, blisters and feels hot because it is exposed to and reacts with radiation from the sun. It's not that the light is burning us. It's that our flesh has an untoward reaction to radiation. We're being poisoned by the sun.

Tell that to the dinosaurs.

Energy is a culmination of mental activity emitted by the life of the universe. Force is energy. Life force produces energy. The dinosaurs had very tiny under active brains. They simply could not produce the energy needed to continue their own existence.

This is evidenced in today's climate change. As our population increases, and we become more educated and aware of others through our vast communication networks, we are producing more life force; emitting more mental energy. This is changing our environment.

 

[passedpawn]

The term sunburn is a colloquialism. Our skin turns red, blisters and feels hot because it is exposed to and reacts with radiation from the sun. It's not that the light is burning us. It's that our flesh has an untoward reaction to radiation. We're being poisoned by the sun.

Here's some more untoward reactions to the suns radiation. I wish I'd seen this before I rolled my spent projection TV to the curb.

[ame]https://www.youtube.com/watch?v=jrje73EyKag[/ame]

 

[ajdelange]

Opening the fridge will warm your house. True!

Back in the days when a STU was a half rack of equipment we put one in a small room that was not tied into the building's HVAC system. When you turned the thing on it got hot in there so our genius facilities guy went to Home Depot, bought a window air conditioning unit and hung it from the ceiling. I got a call from one of the gals that worked in this area complaining that the A/C must be broken because when they turned it on it got even hotter in there. Our facilities guy was a piece of work.

Since it was mentioned in the title I'll point out the the heat transfer from the A/C unit to the air in the room caused the entropy of that air to increase.

 

[passedpawn]

Light is not heat, but it does carry energy. The light emitted by a bulb definitely does turn into heat when those photons hit something. But, according to this a light bulb is about 2% efficient at turning electricity into light in the first place.

https://en.m.wikipedia.org/wiki/Luminous_efficacy

So, your 60W bulb is already a 58.8W electric heater and the energy carried by visible light is minuscule. You're spreading 1.2W of energy, in the form of light, all over the illuminated surfaces... so how much does the LIGHT from a bulb warm a room? Not much!

If you have LED lights the efficiency is much higher, around 10%, but the light consumes many fewer watts. So again, you end up with a couple of watts carried away as light and the rest turned into heat inside the LED, which radiates away.

What were we talking about? I'm getting a beer.

Right, light is a form of energy, and energy is never destroyed, but it can be converted into another form of energy such as heat.

For the sake of clarity, let's just assume that 60W bulb is 100% efficient - that all of the electrical power goes into light. So, now you have this energy in the form of light bouncing around a room. Where does that energy go when the light is absorbed by the walls? I know it's all converted to something, because when I turn the lights off, it gets dark in there. If, as I claim, all 60W is being turned to heat at the walls, then the 60W 100% efficient bulb is also a 100% efficient heater due to the radiative heating of the walls.

I'm not claiming that you can heat your house by leaving the lights on, but I'm suggesting that there's no point in turning them off since they contribute perfectly to your electric heater's job of heating your house.

 

[GilaMinumBeer]

LED light bulb won't heat a room by itelf, I know that. But my point is that there are NO losses, so just leave it on. ALL of the energy put into it become heat, 100%. I keep saying this over and over and it doesn't seem to register.

When you say "lost to atmospheric wasteland", do you mean it will "heat my house"?

You stop. You stop this non-sense right fvcking now, dammit!

I JUST got my 10 year old into the habit of turning the fvcking light off when he leaves the room.

What's next? You going to try to spin the physics that the piss on the toilet seat saves monies on ass moisturizers?

 

[Homercidal]

Replace all your bulbs with infrared bulbs and get even more heat! (And a cool new ambiance too!)

 

[elbinwyp]

Right, light is a form of energy, and energy is never destroyed, but it can be converted into another form of energy such as heat.

For the sake of clarity, let's just assume that 60W bulb is 100% efficient - that all of the electrical power goes into light. So, now you have this energy in the form of light bouncing around a room. Where does that energy go when the light is absorbed by the walls? I know it's all converted to something, because when I turn the lights off, it gets dark in there. If, as I claim, all 60W is being turned to heat at the walls, then the 60W 100% efficient bulb is also a 100% efficient heater due to the radiative heating of the walls.

I'm not claiming that you can heat your house by leaving the lights on, but I'm suggesting that there's no point in turning them off since they contribute perfectly to your electric heater's job of heating your house.

You are missing a key assumption: that your heat source is also 100% efficient. Technology has moved beyond that though. Ductless Mini-splits are performing at COP's above 2, more than doubling the efficiency of your lights.

 

[ajdelange]

Replace all your bulbs with infrared bulbs and get even more heat! (And a cool new ambiance too!)

If fact you wouldn't. If a device draws 100 watts (not 100 volt-amperes; 100 real watts) it will deliver 341.2142 BTU of heat per hour to the system provided that no energy from it escapes the system. The light inside a plywood box commonly used to keep fermenting beer at reasonable temperature delivers exactly as much heat to the interior of the box as an electric 'heater' of the same wattage. The air conditioner in the STU closet delivered exactly as much heat to that closet as would have been delivered by a heater that consumed the same number of watts.

Apparently several people here don't understand that but neither did the graduate engineer we hired to keep our building's systems running!

 

[GilaMinumBeer]

Replace all your bulbs with infrared bulbs and get even more heat! (And a cool new ambiance too!)

 

[dryboroughbrewing]

I have windows, which means my house is not a closed system, so my absorption of visible spectrum light isn't 100% as they are transparent to most of the wavelengths so emitted. Further my windows are made of a low emissivity glass, which means that they'll preferentially trap non-visible wavelength photons (including all those lovely lovely IR photons that my heater kicks out). But yeah all the light hitting visible light opaque objects would be absorbed.

 

[passedpawn]

I have windows, which means my house is not a closed system, so my absorption of visible spectrum light isn't 100% as they are transparent to most of the wavelengths so emitted. Further my windows are made of a low emissivity glass, which means that they'll preferentially trap non-visible wavelength photons (including all those lovely lovely IR photons that my heater kicks out). But yeah all the light hitting visible light opaque objects would be absorbed.

You'll need to get rid of those windows then But you can leave your closet lights on all winter

 

[Zuljin]

Here's some more untoward reactions to the suns radiation. I wish I'd seen this before I rolled my spent projection TV to the curb.

https://www.youtube.com/watch?v=jrje73EyKag

I will be curb hunting for one soon.