Cost to Run 12 volt Exterior Lighting

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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
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It will actually cost around 20% more for the 12 volt lights using the same wattage. This is due to the loss in the transfromer and to a very slight aditional loss in the 12 volt wires.
Electricity is sold in kilowatt hours. To determin this you take the wattage of the bulbs (if that is not known, you take the voltage and multiply it by the current) and multiply it by the number of hours the bulbs are on. This is watt hours. Then devide by 1000 for the kilowatt hours (KWH). For the 12 volt system, you have to add about 20% due to the aditional losses.
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Watts is watts regardless of voltage. Just add the wattage of all your bulbs and calculate as you would in the house. The reason fancified outdoor lighting is lo voltage and not 'line' voltage is because it's safer since the lines are rarely buried very deep and there's also a much wider variety of fixtures and bulbs in lo voltage.
s

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On Jan 27, 9:30 am, snipped-for-privacy@comcast.net wrote:

They dont use less than comparable wattage 120v lights, probably more since the transformer wastes energy through heat loss and the 12v lights may not be as efficient as 120v bulbs. 760 w would cost me maybe 36$ a month run 12 hrs a day, you have the number 760 watt figure hours used x your eletic rate, a Kill-a-Watt meter is good.
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On Sun, 27 Jan 2008 07:30:36 -0800 (PST), snipped-for-privacy@comcast.net wrote:

12V lights are cheaper to "install" than standard 120V lights because of the cheaper materials involved.
300 x 3 = almost a kilowatt. The average cost per kilowatt, last time I checked, was close to a dime. So you pay about a dime an hour to run your 3 lights.
How did you come to the conclusion that one of your lights is only drawing 160W? If you have a 300W lamp in the fixture and are only getting 160W then something is wrong.
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he said his transformers were using near 760 w, a dime-10c for electric, many pay .15-.18c per Kw, few pay 10c
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On Sun, 27 Jan 2008 08:13:03 -0800 (PST), ransley

I live in Georgia. It is still a dime, but I see now that is well below average.
http://www.eia.doe.gov/cneaf/electricity/epm/table5_6_a.html
Btw I could not find this information at my local utility company's web site.
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Your chart seems to show that a dime is really close to average, everywhere but the New England and Mid-Atlantic states, and California.
JK
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That chart is not the truth after all taxes, no matter what it says. For Illinois and Indiana its both about .125 Kwh, It was even higher this year in Chicago area nearing 0.14c Kwh. Check your bill to see if it agrees.
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Mine is actually cheaper than the chart. I am in WI, and my rate is $. 0099880 per kWh, plus a meter charge of $.22 per day.
JK
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So you're trying to tell us you're not even paying one cent per kwh? You'd better look again.
s

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And he doesnt think the 6.60 a month should be considered in his price of kwh cost
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ransley wrote:

Well, $0.0099.../kWh would be 9.9 mills or roughly 10 cents, not less than 1 by my counting decimal places...
--
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Obviously, you don't understand decimal places. A DIME would be .10 so a bit under a time would be .099blahblahblah.
your example of$0.0099 is ALMOST a penny
s

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I adds a 6/10th's of a cent to my cost per kWh
JK
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Yeah well that chart has kansas at 8 cents. Must be about a decade old. You'd better chek your bill Kansas is paying 13+ cents. Your utility company has to post the rates.
s

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That inacurate chart does say 07
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he was referring to the transformers, not the lights themselves. Obviously you would not have a single 300w light on lo voltage.
s

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That's for a kilowatt-HOUR.
Nick
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On Jan 27, 10:30 am, snipped-for-privacy@comcast.net wrote:

buy a kill-a-watt brand meter from around $30 and up and plug it in. to determine your power price, ignore the pennies and look at the delivered price for usage in your case. take the total price of the electric bill and divide it by the kilowatt hours equals cost per kilowatt hour delivered times the number of kilowatt hours your device uses. the more expensive kill-a- watt meter has more cost analysis. it is a cross between a clamp-on ammeter, a recording timer, and a calculator. outdoor lighting is fun, enjoy it. see: http://www.energyfederation.org/consumer/default.php/cPath/388
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