CFLs.... are they efficient ?

they are

of course. With all lighting techs most of the energy is wasted as heat. Most efficient is low pressure sodium, yet they're getting replaced with LEDs!

Incandescent lamps about 10-12 lm/W, (compact) fluorescent lamps about

30 lm/W, some bearable LEDs about 100 lm/W, some LEDs with bad Ra well above 100 lm/W.

The analogy I like is that "zero calorie" soda sweetners don't actually have zero calories, the sweetners used have about the same amount of calories gram for gram, but are ~200 times as sweet as sugar.

** There is a filament at each end of the U or spiral tube that runs hot - just like regular long tube fluoros.

** Regular incandescent lamps give only about 2% of the input energy as useful light. CFLs do much better at 7% to 10% and long tube fluoros are better again.

LED lamps have no wasteful heaters so are better still.

Recent LED examples made in the same styles as incandescent lamps using unbreakable plastic ( not glass) have every possible advantage.

.... Phil

Not true. Aspertame, for example, is indeed 200 times as sweet as sugar but it contains no food energy. Same for saccharin.

CFLs *are* more efficient than incandescents but that doesn't mean that they are 100% efficient. They still waste a lot of energy as heat, only less so than incandescents.

Efficiency doesn't mean temperature, it means ratio of energy in to useful light out. CF (a Philips bulb that I take to be typical) gives about 70 lm/watt, and LED (another Philips bulb) gives 94 lm/watt according to the manufacturer's data.

The LED may dim as it ages, and 30% at 3 years (not unusual) would make it the same as the CF. Both types are efficient compared with incandescent.

Aspartame breaks down to its component amino acids in the intestine; not sure how it couldn't have food energy the same as anything else that's broken down to amino acids during digestion e.g. proteins.

Don't know about saccharin but apparently it hasn't been used in diet sodas in decades, except Tab. Yuck.

Right. CFLs still output 90% of the energy as heat (98% for incandescents).

Look it up.

That was just two examples. The whole idea of artificial sweeteners is that they don't contain dietary calories.

For a given size, temperature is a reasonable measure of efficiency. A29, CFL, and the A29 replacement LEDs are close to the same size so it's a reasonable estimation.

But incandescent bulbs start out at 2-3% luminous efficiency, CFL

8-10%, and LEDs around 20%, so even with a 30% loss, either CFL or LED is a big win for many applications (if you can get past the other issues).

why?

Some discredited study showed it caused cancer in lab rats, but the marketing damage was done, probably.

Looking at the can in front of me it looks like Tab contains both (girlfriend likes the stuff, some NYC thing, tastes like a watered-down Diet Coke to me):

Bullshit. Marketing wants to, and FDA allows them to, claim it as zero. _They're rounding down_.

Same reason they can claim spray cooking oil as "low fat" or "fat free" -- a uselessly short spray is a gram or two of product (or less), which they round down to zero. Or to a small enough fraction of %DV that it's "low".

The only sweeteners that don't give dietary calories are the ones that aren't metabolized. Sugar alcohols come to mind (hence why they are laxative!).

There's also the distinction between dietary calories and chemical calories. The former depends on what the food is, chemically, as well as how it's structured (you can't digest cellulose at all, but you also can't digest raw foods very well -- "insoluble fiber", whereas cooking breaks down cells, releasing a lot of dietary calories). The latter is simply what it burns as.

Tim

--
Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Contract Design 
Website: https://www.seventransistorlabs.com/

Cite.

Tim

--
Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Contract Design 
Website: https://www.seventransistorlabs.com/

If they're too hot to touch then either you have extremely sensitive hands or they're not CFL.

not so.

I guess a lot depends on what the OP meant by 'touched' and if he used the term 'burned' literally or as a figure of speech.

I haven't used many CFLs in the house. I went mostly from incandescents to 4-foot tubes to LEDs. The few CFLs I used were too hot to grip firmly but not too hot for a brief touch, certainly not enough to burn.