I’m pretty dumb with regards to anything to do with this topic.
Now that we’re done with the explanation, my question!
I’ve put two bulbs in my room, one 40W and one 60W. I was wondering whether it would make more sense to put in a single 100W bulb in place of these two. I mean, is it more economical to use a single bulb than two.
We run a 220V system here (if that makes any difference!).
I think it shoud be the same.
The benifit of 2 globes over one is that 100W will being to annoy your eyes in .00003733 Milliseconds.
It’s just the same. 100 W either way. If you want to try econoomy, get a compact fluorescent globe. Catch is, they’re way more expensive to start with, and in my experience, don’t last long enough to pay for themselves.
You need to compare the lumens that each bulb puts out relative to its power consumption - you most certainly cannot just say that two 50-watt bulbs are the same as one 100-watt bulb.
For example - 2 50-watt bulbs may each put out 1000 lumens, but the single 100-watt bulb may put out 2200 lumens. Which is more efficient here? The 100-watt bulb.
HOWEVER…this ignores a critical factor of human ergonomics, which is the lighting effectiveness. Depending on where your 100-watt bulb is located, you may end up with less functional and useful light. Or light that is too heavily concentrated in one area. Take a look at the space you are lighting, reflectivity of the walls, ceiling, and floor, and the items within it. Using two 50-watt bulbs, even if they produced less lumens/watt, may end up being better from a quality of light standpoint.
There is no easy single answer to this question, as a result.
Anthracite: Your answer is correct, but overlooks a practical difficulty. When I’m buying light bulbs in the supermarket, how do I determine their efficiencies? It would be great if the efficiency was printed on the packaging, but it isn’t.
Anthracite is right. And, as a general rule, higher wattage lamps tend to be more efficient. One 100w lightbulb will put out more light than four 25W lamps. At the same time, lower wattage lamps tend to last longer.
As a minor additional note, 100W bulbs will burn hotter than 60 or 40, which may require greater use of cooling fans and/or air conditioning. In addition to buring less electricity, flourescent lights will also produce far less waste heat.
Also higher wattage bulbs usually have a shorter life span then lower wattage (in general) and when it goes you are left in the dark with only one 100W bulb.
Halogen lights are slightly more efficent (apx 80 watts needed) and compact florcent blows both away (about 28-32 watts, even though manu.s would claim less needed).
Distribtution is key. I’d usually rather have distributed, indirect light than something that casts dark shadows.
Well done, hammerbach.
So there is a “bigger is better” trend. The 100 W bulb gives you 1800 lumens, while the 40 + 60 W combination only gives 1380 lumens.
>> As a minor additional note, 100W bulbs will burn hotter than 60 or 40, which may require greater use of cooling fans and/or air conditioning.
Bryan, you may want to think twice. The wattage on the lightbulb is how much power it uses. Tha’t’s the entire point of the thread. One 100W bulb uses 100 watts, just like a 60 and a 40 or like four 25 watt bulbs. The point is that even though the consume the same power and generate the same heat, their luminic efficiencies are not the same.
Are the two light bulbs in the same fixture? If not, then it will probably be better to use two bulbs as the two separate light sources will leave fewer shadows.
Well, actually, the issue in my post wasn’t energy consumption, but waste heat. 60 plus 40 may equal 100, but if the 60 watt bulb burns at 10 degrees above room temperature and the 40 watt bulb burns at 5 degrees above room temperature, that is NOT equivalent to the 100 watt bulb burning 15 degrees above room temperature.
The energy consumed by the bulbs may be small compared to the amount of electric cooling required to reduce the waste heat produced by the bulbs. If the goal is an overall reduction of electricity consumption, waste heat becomes an issue.
Of course, it depends on where the OP lives. If he’s in a northern temperate zone in December, waste heat likely isn’t a major problem right about now.
Anthracite, sailor et al are correct.
All else being equal, I would rather have two bulbs than one. This is because of redundancy. If you use one 100 W bulb, you will be in the dark when it burns out. With two bulbs, however, you will still be able to see when one burns out.
>> Well, actually, the issue in my post wasn’t energy consumption, but waste heat. 60 plus 40 may equal 100, but if the 60 watt bulb burns at 10 degrees above room temperature and the 40 watt bulb burns at 5 degrees above room temperature, that is NOT equivalent to the 100 watt bulb burning 15 degrees above room temperature
Bryan Ekers, you are mistaken in a very bog way. Temperature has nothing to do with how much heat is being put out. the heat being put out is measured in watts and 100 watts is 100 watts no matter which way you slice it. The filament of a flashlight is much hooter than a space heater and yet the space heater puts out thousands of time more heat. Temperature is irrelevant. Power is relevant.
I’m keeping the two bulbs. Many thaks for clearing that up!
Bryan, I live in India.
Hooters and bogs. If you turn out the lights when you read this thread, it is just like being in a B horror movie!
I get the impression sometimes that I’m arguing with someone in a foreign language. If temperature is so irrelevant, I invite you to try an experiment in which you keep a 40-watt, 60-watt and 100-watt lightbulb burning for an hour, then touch each one with your bare hand. Although the 100-watt bulb produces more light, it also burns considerably hotter and of those 100 watts, as many as 90 are being wasted in heat production.
The cost of powering such a bulb may be pretty trivial, but my point is: do you want a 90-watt heat source in your room, whether it produces light or not? If the room is small and naturally warm (as the OP lives in India, I’ll assume so, unless India has cooled down a lot since I was there in 1979) and there are ceiling fans installed to cool it down, having bright incandescent bulbs is a major disadvantage.
The worst case would be a 3-bulb ceiling fan/light with 100-watt bulbs installed in it. Sure, it’s bright, but those bulbs are generating so much heat that you’d have to run the fan constantly while the lights are on to make the room comfortable, and that will raise your electricity bill almost as much as the bulbs themselves. Replacing the bulbs with flourescents, which produce relatively little waste heat, is your best bet if you want to reduce your expenditures on light and cooling.
Actually, concentrating on light bulbs isn’t really the best way to go when it comes to reducing electricity consumption. Major appliances (i.e. anything that has a heating element and/or a motor) are much bigger energy-burners, and anything you can do to reduce their use (i.e. keep your rooms cooler so you don’t need your fans or air conditioning as much) can help your electricity bill significantly, and that includes tracking down and eliminating useless heat sources, including high-wattage incandescent light bulbs.
My typos are terrifying _
The feeling is mutual so I give up. We had a thread discussing this already and I am not about to redo it.