In article
,
ransley wrote:

On Jan 27, 11:26*am, Smitty Two wrote:
In article
,





*ransley Mark wrote:
On Jan 27, 10:18*am, "Pete C." wrote:
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.- Hide
quoted text -

- Show quoted text -

There is light bulb efficency, 100 watt incandesant 120v are around
17-19 Lumen per watt, 4 w 120v can be near 10 LPW then there is the
rating for 12v which per watt could easily make 12v, 20%+ less
efficent.

Well, we aren't talking about lumens. I don't think the OP is looking
out at his rhododendrons and thinking, ****, that damn light doesn't
look like it's putting out an honest quantity of lumens. He's talking
about watts, and the cost to operate those watts.- Hide quoted text -

- Show quoted text -

The OP said he was under the impression 12v is cheaper to run, LPW is
what lighting is all about. Nobody has even thought that those 12v
lights are less efficient in the equation. .

Lumens per watt may be what *interior* lighting is all about, and even a
lot of *outdoor* lighting like football stadiums. As far as lighting up
a path or a flower, it's just mood lighting. I've never heard of anyone
taking LPW efficiency into consideration with landscape lighting, and I
doubt the OP cares about that, either. I think he may have just been
under the mistaken impression that a watt-hour of 12 volt stuff was
cheaper than a watt-hour of 120 volt stuff. Lumens may be an interesting
ancillary consideration from a theoretical perspective, but it's
irrelevant to the OP's considerations.