More heat than light? Incandescent vs CFL vs LED

[sciphi]

I'll be the yahoo who is glad to not be paying an arm and a leg to comfortably light up spaces that need light. That energy needs to go to lighting the space, not heating it up. Some heat is a byproduct of the conversion from electrical energy to light energy, and that's unavoidable with present-day bulbs.

No issues here with using incandescents where appropriate, like the oven or in terrariums that need the light and heat. Other places like the fridge, I'm glad to see lower-heat light sources used. Paying to dissipate the heat from an incandescent bulb in an intentionally cold area doesn't make much sense.

Lastly, from an aesthetic perspective, having thermal management move down the list of considerations when designing a lighting fixture opens up a lot more flexibility for design. With LED being able to effectively have a lot of point sources that can be diffused sure looks different than incandescent where the light comes from a point source.

 

[hatt]

Originally Posted By: Wolf359


Like I said, I don't think you're from the STEM field. That's what a manual J calculation does, it's a heat loss calculation. If you did the math, the heat from a light bulb is negligible. That's why it's not a factor for all the reasons I mentioned earlier.


How is the amount of heat from a light bulb negligible? 90% of the electricity going to it is converted to heat. Go ahead and show the math.

 

[Wolf359]

Originally Posted By: hatt
Originally Posted By: Wolf359


Like I said, I don't think you're from the STEM field. That's what a manual J calculation does, it's a heat loss calculation. If you did the math, the heat from a light bulb is negligible. That's why it's not a factor for all the reasons I mentioned earlier.


How is the amount of heat from a light bulb negligible? 90% of the electricity going to it is converted to heat. Go ahead and show the math.


Well about 95% of the bulb output of a regular incandescent light bulb is heat. So convert your 60 watts bulb X 95% gives you about 57 watts as heat. Convert 57 watts to BTUs which is about 3.412 BTUs per watt or about 194 BTUs. Now most heating systems are anywhere in the range of 60-150k btu's with some monster systems in the 200k range. The actual percentage is left as an exercise for the student.

 

[hatt]

Originally Posted By: Wolf359
Originally Posted By: hatt
Originally Posted By: Wolf359


Like I said, I don't think you're from the STEM field. That's what a manual J calculation does, it's a heat loss calculation. If you did the math, the heat from a light bulb is negligible. That's why it's not a factor for all the reasons I mentioned earlier.


How is the amount of heat from a light bulb negligible? 90% of the electricity going to it is converted to heat. Go ahead and show the math.


Well about 95% of the bulb output of a regular incandescent light bulb is heat. So convert your 60 watts bulb X 95% gives you about 57 watts as heat. Convert 57 watts to BTUs which is about 3.412 BTUs per watt or about 194 BTUs. Now most heating systems are anywhere in the range of 60-150k btu's with some monster systems in the 200k range. The actual percentage is left as an exercise for the student.
95% certainly doesn't sound negligible. Of course a 60 watt appliance isn't going to heat Cowboys Stadium. The 194 BTUs coming out of the lamp is heat your heating system doesn't have to produce. The bulb became much more efficient in this scenario.

 

[greenjp]

Originally Posted By: hatt
95% certainly doesn't sound negligible. Of course a 60 watt appliance isn't going to heat Cowboys Stadium. The 194 BTUs coming out of the lamp is heat your heating system doesn't have to produce. The bulb became much more efficient in this scenario.

I don't think you understand what's being said in this thread. A few points to hopefully clear things up:
- the calculations used for determining the required amount of heating and cooling for a building do already include things like heat added to the space by electricity consuming devices. So your suggestion that you must account for them is in fact correct but also not anything new. Energy consuming devices, occupants, ambient conditions, fresh air ventilation/infiltration, solar load, etc are all already included in these calculations. And to Wolf's point, lighting is generally a pretty small contributor, whether it's incandescent or LED.
- in any area with a cooling season, the extra heat introduced to the space by inefficient devices must be removed, so any "benefit" in the heating season is likely offset in the cooling season.
- the "95% efficient" heat from a lamp is an incomplete way to look at it. Start with the fuel, natural gas for instance. Run it through an efficient power plant and you get 60% efficiency at best. Take another 5% for transmission and distribution and that 95% is actually 54%. Burn that same natural gas in basic forced air furnace and you get 80%, 95%+ if you have a high efficiency condensing system. Or use that electricity to power a vapor compression cycle (heat pump) and it's used much more efficiently than simple resistance heating.
- FWIW you don't actually worry about the efficiency of something like a light bulb in the calculations, you simply use the power consumed. Thermodynamically it doesn't matter what form the electricity is converted into, unless it actually escapes the house.

jeff

 

[hatt]

Originally Posted By: greenjp
Originally Posted By: hatt
95% certainly doesn't sound negligible. Of course a 60 watt appliance isn't going to heat Cowboys Stadium. The 194 BTUs coming out of the lamp is heat your heating system doesn't have to produce. The bulb became much more efficient in this scenario.

I don't think you understand what's being said in this thread. A few points to hopefully clear things up:
- the calculations used for determining the required amount of heating and cooling for a building do already include things like heat added to the space by electricity consuming devices. So your suggestion that you must account for them is in fact correct but also not anything new. Energy consuming devices, occupants, ambient conditions, fresh air ventilation/infiltration, solar load, etc are all already included in these calculations. And to Wolf's point, lighting is generally a pretty small contributor, whether it's incandescent or LED.
- in any area with a cooling season, the extra heat introduced to the space by inefficient devices must be removed, so any "benefit" in the heating season is likely offset in the cooling season.
- the "95% efficient" heat from a lamp is an incomplete way to look at it. Start with the fuel, natural gas for instance. Run it through an efficient power plant and you get 60% efficiency at best. Take another 5% for transmission and distribution and that 95% is actually 54%. Burn that same natural gas in basic forced air furnace and you get 80%, 95%+ if you have a high efficiency condensing system. Or use that electricity to power a vapor compression cycle (heat pump) and it's used much more efficiently than simple resistance heating.
- FWIW you don't actually worry about the efficiency of something like a light bulb in the calculations, you simply use the power consumed. Thermodynamically it doesn't matter what form the electricity is converted into, unless it actually escapes the house.

jeff
You're arguing points that I'm not arguing. Unfortunately you didn't clear up anything.

 

[Wolf359]

Originally Posted By: hatt
Originally Posted By: greenjp
Originally Posted By: hatt
95% certainly doesn't sound negligible. Of course a 60 watt appliance isn't going to heat Cowboys Stadium. The 194 BTUs coming out of the lamp is heat your heating system doesn't have to produce. The bulb became much more efficient in this scenario.

I don't think you understand what's being said in this thread. A few points to hopefully clear things up:
- the calculations used for determining the required amount of heating and cooling for a building do already include things like heat added to the space by electricity consuming devices. So your suggestion that you must account for them is in fact correct but also not anything new. Energy consuming devices, occupants, ambient conditions, fresh air ventilation/infiltration, solar load, etc are all already included in these calculations. And to Wolf's point, lighting is generally a pretty small contributor, whether it's incandescent or LED.
- in any area with a cooling season, the extra heat introduced to the space by inefficient devices must be removed, so any "benefit" in the heating season is likely offset in the cooling season.
- the "95% efficient" heat from a lamp is an incomplete way to look at it. Start with the fuel, natural gas for instance. Run it through an efficient power plant and you get 60% efficiency at best. Take another 5% for transmission and distribution and that 95% is actually 54%. Burn that same natural gas in basic forced air furnace and you get 80%, 95%+ if you have a high efficiency condensing system. Or use that electricity to power a vapor compression cycle (heat pump) and it's used much more efficiently than simple resistance heating.
- FWIW you don't actually worry about the efficiency of something like a light bulb in the calculations, you simply use the power consumed. Thermodynamically it doesn't matter what form the electricity is converted into, unless it actually escapes the house.

jeff
You're arguing points that I'm not arguing. Unfortunately you didn't clear up anything.



You just don't understand heating. Look up heat loss calculation, Manual J. Most heating systems come either as 60,000, 90,000, or 120,000 or even more depending on the size of the house. Even if you have 20 60 watt regular bulbs, 4k worth of BTU doesn't really do much for you and like I said, a proper manual J calculation would also factor those in and they're very minor. Most heating systems are over sized anyway so that they can warm up the house quicker, but long term, it's less efficient due to short cycling. You have a forest/trees problem or a penny wise, pound foolish pursuit of things. A basic rule of thumb around here is that heating with electricity is 2-3x more than gas/oil. Of course depending on the gas/electric rate in your area, this might not apply. You are better off heating with gas or oil than electricity. That's what everyone is trying to tell you and that you don't get. It's basically the difference between a $200 gas bill and a $600 electric bill.

 

[hatt]

You're also arguing points I'm not arguing. No where did I recommend buying light bulbs to heat your house.

Is this true or false? One word answer.

Quote:
The 194 BTUs coming out of the lamp is heat your heating system doesn't have to produce. The bulb became much more efficient in this scenario.

One word answer.

 

[greenjp]

Originally Posted By: hatt
You're also arguing points I'm not arguing. No where did I recommend buying light bulbs to heat your house.

Is this true or false? One word answer.

Quote:
The 194 BTUs coming out of the lamp is heat your heating system doesn't have to produce.

True. It's also 194 BTUs your cooling system must remove.

Quote:
The bulb became much more efficient in this scenario.

I'm not even sure what this is supposed to mean. Since the heat is sorta useful in the winter the bulb is therefore more efficient? I guess that's true in an overly simplistic way. What would be even more efficient would be to use a more efficient bulb to generate the required light and then make up the required heating difference with an even more efficient heating source.

I guess I can't even tell what point you're trying to make.

jeff

 

[Wolf359]

Originally Posted By: greenjp
Originally Posted By: hatt
You're also arguing points I'm not arguing. No where did I recommend buying light bulbs to heat your house.

Is this true or false? One word answer.

Quote:
The 194 BTUs coming out of the lamp is heat your heating system doesn't have to produce.

True. It's also 194 BTUs your cooling system must remove.

Quote:
The bulb became much more efficient in this scenario.

I'm not even sure what this is supposed to mean. Since the heat is sorta useful in the winter the bulb is therefore more efficient? I guess that's true in an overly simplistic way. What would be even more efficient would be to use a more efficient bulb to generate the required light and then make up the required heating difference with an even more efficient heating source.

I guess I can't even tell what point you're trying to make.

jeff


He doesn't really understand all the stuff that's been said in the thread. Regular electric heat is basically 100% efficient. Therefore a light bulb that's only 95% efficient is actually less efficient than regular electric heat as a percentage of electricity gets covered to light and the rest is heat. However if you compare the cost of the heat from the electricity vs the cost of using gas to heat the home, gas is way cheaper. Sorta like saying running 100 octane gas will get you more power, but if it costs you 2-3x as much, it's not suitable for every day driving.

 

[hatt]

Originally Posted By: greenjp
Originally Posted By: hatt
You're also arguing points I'm not arguing. No where did I recommend buying light bulbs to heat your house.

Is this true or false? One word answer.

Quote:
The 194 BTUs coming out of the lamp is heat your heating system doesn't have to produce.

True. It's also 194 BTUs your cooling system must remove.

Quote:
The bulb became much more efficient in this scenario.

I'm not even sure what this is supposed to mean. Since the heat is sorta useful in the winter the bulb is therefore more efficient? I guess that's true in an overly simplistic way. What would be even more efficient would be to use a more efficient bulb to generate the required light and then make up the required heating difference with an even more efficient heating source.

I guess I can't even tell what point you're trying to make.

jeff
Like pulling teeth around here. But anyway. That's all I've been saying.

 

[hatt]

Originally Posted By: Wolf359
Originally Posted By: greenjp
Originally Posted By: hatt
You're also arguing points I'm not arguing. No where did I recommend buying light bulbs to heat your house.

Is this true or false? One word answer.

Quote:
The 194 BTUs coming out of the lamp is heat your heating system doesn't have to produce.

True. It's also 194 BTUs your cooling system must remove.

Quote:
The bulb became much more efficient in this scenario.

I'm not even sure what this is supposed to mean. Since the heat is sorta useful in the winter the bulb is therefore more efficient? I guess that's true in an overly simplistic way. What would be even more efficient would be to use a more efficient bulb to generate the required light and then make up the required heating difference with an even more efficient heating source.

I guess I can't even tell what point you're trying to make.

jeff


He doesn't really understand all the stuff that's been said in the thread. Regular electric heat is basically 100% efficient. Therefore a light bulb that's only 95% efficient is actually less efficient than regular electric heat as a percentage of electricity gets covered to light and the rest is heat. However if you compare the cost of the heat from the electricity vs the cost of using gas to heat the home, gas is way cheaper. Sorta like saying running 100 octane gas will get you more power, but if it costs you 2-3x as much, it's not suitable for every day driving.
zzz. Still arguing things I've never said.

 

[greenjp]

Originally Posted By: hatt
Originally Posted By: greenjp
Originally Posted By: hatt
You're also arguing points I'm not arguing. No where did I recommend buying light bulbs to heat your house.

Is this true or false? One word answer.

Quote:
The 194 BTUs coming out of the lamp is heat your heating system doesn't have to produce.

True. It's also 194 BTUs your cooling system must remove.

Quote:
The bulb became much more efficient in this scenario.

I'm not even sure what this is supposed to mean. Since the heat is sorta useful in the winter the bulb is therefore more efficient? I guess that's true in an overly simplistic way. What would be even more efficient would be to use a more efficient bulb to generate the required light and then make up the required heating difference with an even more efficient heating source.

I guess I can't even tell what point you're trying to make.

jeff
Like pulling teeth around here. But anyway. That's all I've been saying.

Got it. My (and Wolf's I assume) point is that the point you're making is utterly pointless without context.

 

[Wolf359]

Originally Posted By: greenjp
Got it. My (and Wolf's I assume) point is that the point you're making is utterly pointless without context.


Yes, I think the point he was making was like saying water is wet and you better account for that when you go swimming.

 

[hatt]

Originally Posted By: Wolf359
Originally Posted By: greenjp
Got it. My (and Wolf's I assume) point is that the point you're making is utterly pointless without context.


Yes, I think the point he was making was like saying water is wet and you better account for that when you go swimming.

Clearly my point was over your head. You should get out more. I'm sure you got all your old bulbs changed out so you can save a few bucks on your electric bill. Live a little. You'd lose your mind if you seen the bulbs I have in pendants over the bar. Freaking squirrel cage incandescents. They hardly put out any light. And don't seem to get very hot either. They just use a lot of electricity. I do have a bunch of LEDs in the kitchen cans, over the fireplace, in the hall. Since they're so energy efficient they stay on pretty much all day. Victim of Jevons's paradox. When I wanted to save money on my electric bill years ago I had a bunch of extra insulation blown in the attic instead of buying expensive light bulbs that I'd need an audit to see the difference.

I forgot to mention. I turn the fireplace lights off sometimes, when I have the oil lamps burning.

 

[Wolf359]

Originally Posted By: hatt
Originally Posted By: Wolf359
Originally Posted By: greenjp
Got it. My (and Wolf's I assume) point is that the point you're making is utterly pointless without context.


Yes, I think the point he was making was like saying water is wet and you better account for that when you go swimming.

Clearly my point was over your head. You should get out more. I'm sure you got all your old bulbs changed out so you can save a few bucks on your electric bill. Live a little. You'd lose your mind if you seen the bulbs I have in pendants over the bar. Freaking squirrel cage incandescents. They hardly put out any light. And don't seem to get very hot either. They just use a lot of electricity. I do have a bunch of LEDs in the kitchen cans, over the fireplace, in the hall. Since they're so energy efficient they stay on pretty much all day. Victim of Jevons's paradox. When I wanted to save money on my electric bill years ago I had a bunch of extra insulation blown in the attic instead of buying expensive light bulbs that I'd need an audit to see the difference.

I forgot to mention. I turn the fireplace lights off sometimes, when I have the oil lamps burning.

Yes, it was clearly over everyone's head. What was your point again?