Brendan Hughes

Bit **** maybe, but curiosity could be put to worse ends...

I was brought up, by economising parents , to turn the light off when I leave the room to save electricity.

I also know that turning lights (off and) on uses more electricity than leaving them on for a short period of time, as there is some sort of surge of electricity as they are switched on (and it increases wear on the filament). So if you're re-entering the room "soon", it's better to leave them on.

I'm now next to the office meeting room, and it annoys me to see the 16 lights left on even when there's no-one in it.

Can anyone give an rough idea of the "break-even" point, ie the minimum time they should be off before it's truly economic, taking into account the above surge / wear?

I presume the answer will be different for tungsten filament bulbs and the modern "economy" ones.

Cheers

Faire D'Income

You had electricity when you were growing up?

logiclee

Tungsten bulb's do not have any costly surge when being switched on. You would have to measure the increase in power usage with very accurate meters and that would only be for a fraction of a second.

Flourescent fittings do have a power surge when switched on to get them to strike but your talking tiny fractions of a penny to switch on a standard 5' fitting. Modern electronic starters are even more efficient as well.

Other slow startling lamps such as Sodium lamps are a little different but not used generally indoors or at home.

As for switching lights off at home etc. Its a good idea but won't make you rich.
You could leave on a 20W energy saving lamp (100w output) for 50 hours and it would cost you one unit of electricity, so about 6p.

Lee

Tiggs

whatever the figure is less than your hourly rate at work that you have just wasted thinking about it!

r32

Make sure you leave the plugs in the sockets as you dont want the electricity running out.

Brendan Hughes

Really? Thanks Lee. Ah well, another one to add to the "urban myths" list.

(saving electricity that is, not the fact that I had it when growing up )

Still, I'll carry on reading the Guardian, wearing sandals and feeling self-righteous if nothing else.

Tiggs - scoobynet is responsible for a lot, LOT worse than that...

logiclee

If you happen to have a massive induction motor your issue maybe relevant.

Say a 3000hp induction motor direct drive onto something like a fan may take 500% of normal load for 30 seconds on start up.

It would have to be stood for more than two and a half minutes to make up for a start. You may even be charged for the extra demand by the electricity supplier depending on your agreement so financialy maybe even longer.

In reality you wouldn't stop/start such a big machine anyway, the equipment wouldn't last long under the stress of repeated starts.

Lee

Diesel

What about the telly/DVD etc then?

I tend to leave all the electronic kit at work on all the time as it tends to get used 14 hours a day (although not weekends). The continual PCB expansion and contraction due to heat when switching things off and on is probably worse - leave them at working temp I say, they'll last longer and be more reliable & stable...?

However I think my home DVD takes 20watts even in standby, which is more than most of the low energy bulbs I have!!!

Hmmm!?

David_Dickson

my boss made a point of telling me that switching the lights on in the store used more power than leaving them on (loads of flourescent tubes)

I make a point of flicking them on and off a few times before I enter, then leave them on when i leave