# Power/Money saving



## Pudsey_Bear (Sep 25, 2008)

How does a 240v transformer use less electricity.

IE 240v 50watt dichroics, V 12v GU10 LEDS lamps.

Struggling to get my head around this Googled it but not found a simple explanation of how it saves energy/money.

Sorry for being in thick mode.


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## spykal (May 9, 2005)

Hi kev

A bit heavy for early sunday morning but here is my explanation... 

The amount of power used by electrical devices is expressed in watts so really you need to consider the wattage of each type rather than the voltage.

the LED lights will have a much lower wattage for the same amount of emitted light ... the 12v LEDs will convert the electrical energy to light energy in a much more efficient manner than the Gu10 bulbs that have a filament... these "waste" energy by converting a large proportion into heat.

So even allowing for the loss in the transformer ( heat given off) the overall efficiency of the system using LEDs will be much better.


Mike

P.S.
Another good principle to keep in mind is that energy cannot be created or destroyed ....it can only be changed from one form to another.
(The first law of thermodynamics...if you want to google it :wink: )


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## zappy61 (May 1, 2005)

As I recall Kev, I don't think it does, watts is watts if the appliance or bulb is 50 watts then the output is 50 watts regardless of the voltage. The amps are different (watts divided by volts), for a 50 watt 12v the amps are 4.17 and for a 240v 0.21. If the G10 bulbs are led or energy saving they will be low wattage and save you money. 

Graham


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## spykal (May 9, 2005)

zappy61 said:


> As I recall Kev, I don't think it does, watts is watts if the appliance or bulb is 50 watts then the output is 50 watts regardless of the voltage. The amps are different (watts divided by volts), for a 50 watt 12v the amps are 4.17 and for a 240v 0.21. If the G10 bulbs are led or energy saving they will be low wattage and save you money.
> 
> Graham


Hi Graham

You said " if the appliance or bulb is 50 watts then the OUTPUT is 50 watts regardless of the voltage"

Not really wanting to be picky but my understanding of this would have you saying " if the appliance or bulb is 50 watts then the INPUT is 50 watts regardless of the voltage"

The true output of a traditional light bulb will be a total of the light energy plus any heat energy.

Traditional light bulbs are really bad at converting electrical enegy into light .... nearly 90% of the energy is converted into heat only about 10% is converted into light.

So the saving gained by using LEDs is because a low wattage LED gives out the same amount of light as a much higher wattage traditional bulb.

Sorry to have expanded on my earlier post... not trying to be clever, honest :roll:

Mike


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## zappy61 (May 1, 2005)

spykal said:


> zappy61 said:
> 
> 
> > As I recall Kev, I don't think it does, watts is watts if the appliance or bulb is 50 watts then the output is 50 watts regardless of the voltage. The amps are different (watts divided by volts), for a 50 watt 12v the amps are 4.17 and for a 240v 0.21. If the G10 bulbs are led or energy saving they will be low wattage and save you money.
> ...


I agree Mike but what you pay for via the meter is 50 watts.

Graham


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## Andysam (May 10, 2005)

Dunno, but all of my 240v GU10 50w bulbs were changed to 11w CFLs and they are now being slowly phased over to LEDs. The was a power saving each time according to my energy monitor.

For the record I am NEVER having GU10 bulbs again. They blow regularly and cost a fortune. I could have installed 10 double strip florries in the kitchen for what I've spent on those things. :evil: 

Florries it is next time then!


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## Pudsey_Bear (Sep 25, 2008)

My current (sorry) direction is towards GU10 LEDs as these seem to be far more reliable than Halogen anyway and more energy efficient.


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## pippin (Nov 15, 2007)

Kev:

_ie 240v 50watt dichroics, vs 12v GU10 LEDS lamps._

GU10 are never 12V, they are a 240V standard.

50W dichroics are 12V MR16.

You have mixed the two up.

All LED lamps have voltage reducers in-built as they only need a couple of volts to operate, however they are packaged or what supply is used.

That is why they can still get quite warm

However the rules about watts still apply, especially the inefficiency of filament lamps.

PS

Lamps is lamps, bulbs are what you plant in the garden!


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## Pudsey_Bear (Sep 25, 2008)

pippin said:


> Kev:
> 
> _ie 240v 50watt dichroics, vs 12v GU10 LEDS lamps._
> 
> ...


Never one to argue, as you know But click here am I still wrong, as for bulbs, I thought you put them in lamps, as in light bulbs, is it me :?: :?: :lol: :lol: :lol:


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## spykal (May 9, 2005)

Hi Kev

Might not be a good idea to buy from him ...it seems that the seller is more confused than you ...a right dichroic head :lol: 


Mike


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## pippin (Nov 15, 2007)

Kev

"*Them's lamps sonny, bulbs is what you plant in the garden*" is what the old electricians on board ship used to snarl at us when we asked for a light bulb.

And who am I to gainsay their wisdom!!


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## joedenise (Jul 20, 2007)

I agree with pippin you plant bulbs 

joe


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## H1-GBV (Feb 28, 2006)

Electricity is wonderful stuff - lots of numbers, lots of confusion, lots of danger so it's worth getting a bit of an idea of what is going on.

A long time ago, Georg Ohm discovered the concept of resistance (measured in ohms). If you apply 10V to a 50ohm resistor, 0.2 amps (that's current) will flow [I (what an odd symbol to use for current) = V/R = 10/50 =0.2]

If you apply 20V, 0.4A will flow [I=20/50 = 0.4]. And so it goes - apply a bigger voltage to a fixed resistor and the current will go up proportionaly.

However, as you may have heard earlier, power (measured in watts - W) is the product of current and voltage. In our 2 examples: P=I*V = 0.2*10 = 2W and P=I*V = 0.4*20 = 8W. As you can see, doubling the voltage has also doubled the current, so the power (energy per second) has quadrupled.

If you apply 12V to a typical car headlamp, you will expend 50W ie you get a current of just over 4A. Reduce that to 6V and you get about 2A and the power is down to 12.5W. Apply 24V and you might get over 8A -> 200W. However, more likely is a burnt out filament, as the wire inside is not designed to handle that much current, so it melts.

You can apply 240V ac to a transformer and reduce it to 12V (or any other voltage you require; it's a question of the number of turns wound on the transformer). As mentioned, energy cannot be created nor destroyed, so 12V, 4A (=48W) at the output would require 240V, 0.2A (=48W) as the input if the transformer is 100% efficient (which is not unreasonable).

So it's not a quetion of getting less or more electricity; you are changing one value (voltage) and another changes automatically, with the resistance being a major controlling factor. Although confusing, and potentially dangerous, just following instructions usually keeps things safe.

HTH - Gordon


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## Pudsey_Bear (Sep 25, 2008)

I know a few places where if you asked for a lamp, you'd get a thick ear :lol: :lol: 

Still no wiser as to watts watt :roll: :roll: :roll: :roll:


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## sallytrafic (Jan 17, 2006)

Lamps are for glowing
Bulbs are for growing

trust me I was a lighthouse engineer.


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