Ralph Mowery wrote:
"Smitty Two" wrote in message
news
In article
,
wrote:
I use three, 300 watt 12 volt Maulibu type transformers to light my
yard and walkway lights around my home.
I was under the impression the reason one would use 12volt instead of
line voltage was the 12v was less costly to run.
How do I determine how much power each of these is drawing (per hr?)
so I calculate my cost per month. I don't think it will matter, but
one of them is only drawing about 160 watts. Each of the others is
near their 300 watt limit.
Thx
A watt is a watt. It doesn't matter whether it's 12 volts or 120 volts.
Since a watt is a volt times an amp, the low voltage bulb will draw 10
times as much current as the 120 volt bulb of the same wattage. For cost
to operate, all you have to consider is watt-hours.
While a watt is a watt with lights, the 12 volt system will cost about 20%
more to run if the same wattage of bulbs is used. This is because of the
transformer loss and a small aditional loss in the 12 volt wiring compaired
to the 120 volt wiring..
The 12 volt system is used mainly due to the safety factor. If a dog chews
into the 12 volt system, he will receive a small charge and not be harmed
where the 120 volt system will probably kill.
You've got your decimal point in the wrong place. Transformer and wiring
losses will be more like 2%, not 20%.
As for not electrocuting some filthy dog crapping on my lawn, digging in
my landscaping and chewing my wiring, I'm not sure low voltage is a good
thing. I'm thinking I should upgrade to 480V landscape lighting.