Energy Saving Bulbs - best to leave them on???

bagpuss_fan

I have recently changed most of the bulbs in my house to energy savers. I have a big old house and my kids leave the hallway lights on all the time, which I constantly tell them off for!!

However, I was told that it costs more if they're always getting turned on and off, and only work properly if you just leave them on, is this true??

Cardew

No its not true.

This is a throwback to the days of the old fluorecent lights that used more electricity in the first few seconds while 'warming up'.

The low energy bulbs do take a few seconds to reach full brightness, but it is always cheaper to switch them off.

However you do need to get savings into perspective. Most bulbs are 8W or 13W so they can be lit for 12 hours or 8 hours for the cost of 1p (1 pence)

bagpuss_fan

Thanks for that, and I'll inform my Dad (who has a flourescent light in his kitchen!)

moonrakerz

Found this on a US website:

"The practical answer is, no, it makes no sense to leave a
fluorescent light (of ANY type) on instead of turning it off.

This is an story that seems to have started over 50 years ago
when someone noticed that the starting current for the first
second or less, of a fluorescent lamp, was higher than its
current draw after that time.

Starting current of a typical fluorescent lamp is in the
neighborhood of 50% more than its normal operating current.
But as I stated above, this only lasts for around a second or
so. Even much less with many types of fluorescent lamps.

Let us take a standard 40 Watt fluorescent tube as an example.
When you turn it on, it draws perhaps 60 Watts for the first
second, then 40 Watts from then on. So, for the first second,
it is using 20 Watts more than normal.

Now, let us say you are walking out of the room for just 10
minutes, and you decide to leave the lamp on, because someone
claimed it would use less energy than if you turned it off,
then on again 10 minutes later. That lamp will be wasting 40
Watts of electrical energy for 10 minutes, before you return
to the room.

But if you switched it off, it would consume no power at all
for that 10 minutes, then when switched back on, it would
consume an extra 20 Watts or so for a mere second or less. So
in this example, leaving it on would use "waste" 40 Watts for
10 minutes. Switching it off would "waste" 20 Watts for a
second or less. Clearly, that old story about leaving
fluorescent lamps running to save power is utter nonsense!"

beach86

Like the OP said, its a myth but a common myth at that. The only problem with EE lighting is the disposal of them but you can just call the council's waste department and ask them where to dispose of them - in 10 years time when they stop working!!!!

geordie_joe

beach86 wrote: »

just call the council's waste department and ask them where to dispose of them - in 10 years time when they stop working!!!!

Or in my case, send them back to Philips when they only work for a few seconds. Or when they die the day after you fit them in the bathroom.

moneysavingwannabe

Hi,

Anyone know if it is best to turn off projector lamps?

At school we all have interactive whiteboards which all have a projector.
I've been telling people to turn them off even for 15 mins but a few people have quoted the "it uses more energy".

unrich

Projector lamps will be tungsten filament.
They use power for all the time they are switched on.
They will be quite powerful 200 to 300 watt bulbs. (or more check the projector).
So just like a non-fluorescent bulb it is best to turn them off when not in use.

Send them to the Physics master if there is an argument about this. (do they still exist?)

Somebody will let us know if I'm wrong.

Cardew

unrich wrote: »

Projector lamps will be tungsten filament.
They use power for all the time they are switched on.
They will be quite powerful 200 to 300 watt bulbs. (or more check the projector).
So just like a non-fluorescent bulb it is best to turn them off when not in use.

Send them to the Physics master if there is an argument about this. (do they still exist?)

Somebody will let us know if I'm wrong.

Above is correct about consumption.

However, IIRC there is a problem with the life of these bulbs as they get very hot, and turning them on and off is not good practice.

moonrakerz

Turning tungsten filament lamps, especially high power ones, will shorten the life of the lamp. This is caused by the filament undergoing extreme changes of temperature when it is switched on and off, this weakens it.

You probably will save electricity by switching it off, but almost certainly will shorten the life of the lamp - swings and roundabouts. With the price of lamps, it's probably better to leave it on.

Also, never move a projector with a high powered lamp until the lamp has been switched off and allowed to cool right down - guaranteed to blow the lamp !

moneysavingwannabe

Hi,

Thanks for your replies, I will rethink what I am telling everyone!

I suppose maybe over an hour lunch period it would be better to turn them off but maybe not for the shorter breaks then?

Thanks again :beer: