Are low energy bulb lifespans misleading?

LosEndos

I needed a 40w candle bulb for my cooker. Got a Philips EcoClassic 28w bulb (£1.49 from Morrisons) and it says 2 years (2000h) on the front of the package.

But on the back there is an icon of an on/off switch with 800 below it. So that means it can be turned on and off 800 times.

Well we turn our cooker light on and off say 4 times a day. So that means it will, on average, last 200 days. Considerably shorter than the 720 days as indicated on the front of the package.

Had a surf about and could find no info on this specification of the bulb and nothing at all on the Phillps web site.

Anyone else notice the unusual specification?

LosEndos

Ah! Here it is on Wiki:

The rated life of a CFL ranges from 8 to 15 times that of incandescent. CFLs typically have a rated lifespan of 6,000 to 15,000 hours, whereas incandescent lamps are usually manufactured to have a lifespan of 750 hours or 1,000 hours.
The lifetime of any lamp depends on many factors, including operating voltage, manufacturing defects, exposure to coltage spikes, mechanical shock, frequency of cycling on and off, lamp orientation, and ambient operating temperature, among other factors. The life of a CFL is significantly shorter if it is turned on and off frequently. In the case of a 5-minute on/off cycle the lifespan of a CFL can be reduced to "close to that of incandescent light bulbs". The U.S. Energy Star program suggests that fluorescent lamps be left on when leaving a room for less than 15 minutes to mitigate this problem.

So that means that if you are using a bulb in a frequent on/off application it is cheaper to stick with incandescent which are cheaper than energy saving to buy and you don’t benefit from the energy saving of a longer life.

k9387

It would be more misleading if they didn't include that caveat.

Count yourself lucky, you are better off than the person who turns it on and off 8 times a day and only gets 100 days...

Seriously though, it makes sence really, it's life (probably mean time before failure) is 2,000hrs or 800 on/offs, whichever is shorter.

I_luv_cats

If you look on the packaging they may say an average daily usage!!!

My Tesco Stick LE says 10 years based on 2.7hrs a day

My Philips Genie Stick says 8 years based on 3 hrs day

My Philips Genie Stick says 10 years based on 10,000 hours

My Philips Softone says 10 years based on 10,000 hours

securityman

it will last 2 years if you dont turn it off.

Ben84

I've been using the Philips eco classic bulbs for years now and am largely still using the first ones I bought, which are now well past their official predicted life in hours. Despite their longevity so far, I have just bought a couple more boxes of 42w bulbs due to frosted bulbs being banned. I just checked these packets and they predict eight-thousand on-off switching cycles, so I wonder if you have missed a zero?

LosEndos

Yep! I'm a nob-head! I miss-read the package and it does say 8000 not 800. Perhaps I should have turned the light on….!

ed110220

The thing to remember is that the life given is an average - some lamps will last longer and some sorter than the stated life. It is measured by the manufacturer as the time until half of the bulbs they test die. Say for instance they test 100 lamps and after 10 000 hours 50 are dead, then the stated life will be 10 000h, but one or two might last only say 1000 hours and a few others 50 000h with the others distributed somewhere in between.

The testing is usually given for a certain number of on/off cycles.

Ben84

LosEndos wrote: »

Yep! I'm a nob-head! I miss-read the package and it does say 8000 not 800. Perhaps I should have turned the light on….!

lol, well hopefully then it will last as long as mine have and help you save electricity.

As a side note, the greater light output of these bulbs isn't just good for saving energy, it also allows you to improve light output where fixtures have a restricting wattage limit. Obviously using higher wattage bulbs can damage the fixture with heat, but swapping to halogen means more light for each watt and you're still within the safe wattage. My cooker hood says no more than 40 watt bulb, which is a bit dim really, so I put a 40 watt halogen in which was much brighter and better.

iamcornholio

We've used CFL bulbs for about 10 years now.

And in that time some fittings have had the bulb changed four-five times, others two and all the rest at least once. So they do not last the 10 years stated.

Another thing is that after two-three years the actual light output dims. You tend not to notice it much if you are using the lights every day, but swap a bulb out for a new one and you definitely see the change in brightness

So whilst the bulbs may still work after a few years, they are so dim as to become unusable and you end up changing them anyway

ed110220

iamcornholio wrote: »

We've used CFL bulbs for about 10 years now.

And in that time some fittings have had the bulb changed four-five times, others two and all the rest at least once. So they do not last the 10 years stated.

Another thing is that after two-three years the actual light output dims. You tend not to notice it much if you are using the lights every day, but swap a bulb out for a new one and you definitely see the change in brightness

So whilst the bulbs may still work after a few years, they are so dim as to become unusable and you end up changing them anyway

Most manufacturers publish light output after a certain length of life, say 95% of initial output after X hours and 90% after Y hours, so it is worth having a look.

Here's an example from Sylvania for their T5 linear flurescents: http://assets.sylvania.com/assets/Documents/PENTRON%20HO%20ECO%20(FL092).f5d24c23-8c8b-4590-9605-765e9b7a39e0.pdf

Expecting even a CFL lamp to last 10 years is a little optimistic, unless it is used little.