This is an old thread, you'd have been better off starting a new one, but anyway, seeing as I'm a regular in this forum, I'm still here
backtothebeer said:
My electician insists that a 50w Halogen Dichoric GU5.3 12V bulb for a ceiling downlight does not actually use 50w of mains electricity.
unless he is being predantic about it because it doesn't actually use any electricity
straight from the mains , then he is wrong, watts are a measure of the rate of transfer of energy, that means for the transformer to be supplying the lamp with 50w, it must be drawing 50w from the mains (unless its magicing energy out of thin air
)
The only slight exception (well not really, but if you interpret the labeling wrong...) to this rule are energy efficeient lamps, they are generally sold on what wattage normal lamp they give out equivelent light to, but take less power to do so (again, no magic, they just dont create anywhere as near as much heat) and typically one equiv. to 60w takes 12w. Anyway thats a side point
Sadly the occasional electrician doesn't seem to get this (Probably spent his time at college smoking and swapping porno mags at the back of the room
)
Do they use 50w - e.g. 10 of them would be 500 watts and for cost of electricity to me I take that as half a KWh?
Yes, that is correct, ten 50w lamps will take 500w, which is half a kilowatt, which means that have them on for an hour and you'll clock up half a Kwh on your meter
Hope that answers your question, though I seem to have digressed a little