If I have electric heat, why turn out interior lights in the winter? Won’t all the light be eventually converted to heat (ignoring that which escapes through the uncurtained windows) just as well as the electric coil in my heater?
Similarly, what about having an efficient gas range? The flame there is the same as the flame in a gas heater?
I figure inefficiency is turned into excess heat, so I just have to run my furnace a bit less hard?
Please help.
So now it’s inefficient the other way. Let’s say that 100% of the energy going into a lightbulb is outputted in the form of either light or heat. Usually, we want just the light, so it’s inefficient. If we want both the light and the heat, then we might be ok. But if we want just the heat, then we’re still being inefficient (the light is going to waste). So, you should only have a light bulb on when you’re in the room.
But when the light goes to waste, waste is in the form of heat, right? It bounces around the walls, and is eventually absorbed into your paint and plaster, warming it, right?
Not quite. Let me try an example: say you had 10 J of energy to use however you wished. You could put them into a heater, using all 10 J to heat your house. Or you could use them in a lightbulb, using 4 J to make heat, and 6 J to make light. If you’re not benefitting from the use of the light, then the 6 J used to make that light is being wasted; either way, you’re using up all 10 J, but in one instance you’re being heated with 6 of them, and in the other, you’re being heated with all 10.
Of course, by 6 in this sentence, I meant 4.
Primarily because an 80 watt lightbulb is horribly inefficient as a heater for a normal sized room? It is more efficient to concentrate on getting the bulb to last longer and use less energy, so the energy can be used in more efficient means.
One analogy is the Matrix fallacy. A human body outputs more energy (as heat) than a lightbulb does, so you could say that paying 20 illegal immigrants to stand around in your room is an efficient heating source… neverminding that you have to feed them massive quantities of food to produce that heat. Humans are inefficient as energy producers.
Nonetheless, I still use my computer as a heater in the winter, and it does an adequate job - but a computer is a different beast than a lightbulb.
mparillo: I was thinking about this a lot a couple years ago when I got some of those energy-saving fluorescent bulbs for my apartment. In fact, I even came up with a scenario whereby they might make the house use more energy: I control the heat in the entire house (made up of 4 apartments) and since my apartment is the only one on the first floor, it is much colder than the rest. So, apparently while I am downright chilly down here, they can be getting quite toasty…in fact too toasty upstairs. Now, what I worried about was that by installing the energy-efficient bulbs, the house would end up running the heat more to keep my place at the same minimum temperature I can tolerate and we’d end up using more energy in the house as a whole than if I had nice heat-producing incandescents helping to heat my apartment a little!
At that point though, I decided I had better just not worry about it or I’d drive myself batty. Clearly, the bulbs do save energy in the ~5 months a year we don’t need much heat in Rochester. Also, you have to account for the differences in efficiency of different sources of energy…Our furnace uses natural gas which is probably more efficient (e.g., in terms of losses before the energy even gets to your house) than electricity.
Oh…I forgot to add that our house does not have air conditioning. When a place has air conditioning, of course, then the heat energy from lightbulbs is not only wasted but actually makes the air-conditioner work harder and you get a double whammy!
The difference with efficient and non-efficient natural gas heaters is that with the latter, a much larger proportion of the heat goes out the chimney.
High-efficiency gas heaters (at least in certain European countries) have elaborate constructs to recover the latent heat from the water vapor in the exhaust gases. This makes a huge difference (large savings) in gas consumption.
Folks, once you have energy in the form of light energy, you can’t just “lose” it, if it’s a self-contained system. So unless you shine the light out a window, it’s going to, for all intents and purposes, be converted to heat. The only thing that’s lost is that you’d spend more money on parts and supplies for the lightbulb.
I mean, what other choices are there…chemical potential, gravitational potential.
Now, this is assuming of course that all the appliances and the power source are in proper phase. Otherwise, the power company might spend more in pumping the energy to you but that’s not your problem 
Modify your thought. You have 10 J of energy to use to heat your home to a given temperature. Using a heater, you use all 10 J for x-period of time to heat the home to a given temperature. If your light bulb uses 5 J for light and 5 J for heat, you need to operate the light bulb for 2x time to achieve the same temperature that only required 1x time from the heater. However, the light bulb consumed 20 J of energy to achieve the same temperature while the heater required half as much energy as the light bulb.
But shouldn’t the issue be energy conservation?
The confusion here, however, is in what happens to the 5 J that goes for light…It is eventually turned into heat too. (Now, it might be possible that some of the light goes through the window or heats the wall in a way that conducts the heat out of the house more rapidly than if you used the heater or whatever, but that introduces additional issues about your home not being a closed system.)
Energy is energy, heat is heat, it doesn’t matter, theoretically, whether it comes from a bulb or electric heater, gas heater or gas stove. Each joule of energy heats your house the same amount. However, in practice it does matter.
The bulb may be right next to your ceiling, where you don’t need heat, where it won’t heat YOU much, and where it will escape fastest. The stove is nestled inside cabinetry, and will primarily heat the kitchen, nice if you’re in there, not so good at 2am when your bedroom is cold and the kitchen warm. In the summer, all that extra heat is nothing but wasted energy, and none of us will go round changing all lightbulbs and appliances twice a year.
So, overall, you’re better off getting the energy efficient versions, that way YOU choose when and where your energy is used. Heat comes from your efficient heating system to the places you need heated when you need heat, and your appliances/lights do their jobs using a minimum of energy.