Low voltage lighting - going greener

[mallorn]

I have some low voltage lights, running between two cables (bought from ikea). There are five 10w 12 volt lamps on the string.

What would be the impact on the transformer if I were to replace these with 1w LED equivalents? It's a long time since I did A level physics.

This would take the power consumption from 50w to 5w.

[buildersmate]

Yes in theory, but it's not quite that simple.
Firstly these LED equivalents are more efficient (produce more light per Watt than conventional/halogen bulbs) but I doubt that they are 5x more efficient (someone else will probably know).
Secondly if you de-load some TXs from their 'normal' rating, the output voltage rises a bit. So test the voltage under this load first because if it rose to say 15V, it would shorten the life of the LEDs (probably). Check the rating plate on the TX if there is one - it might specify a minimum VA load (you could put more LEDs on the string).

[Disco Fever]

Well said Buildersmate, also check the transformer as if it's the electronic type then the tranny wont 'see' the LED lamps as the wattage is lower than the original lamps....