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# cost of hydro

#1
11-04-07, 06:28 AM
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Join Date: Oct 2007
Posts: 5
cost of hydro

how do I figure out how much it costs to run a fixture? I sort of remember a formula from highschool but don't know what it is. I have a barn light which is 400 watts but don't know how many amps. Is it cheaper to switch the light to run on 220 volts vs 120? I pay 5.3 cents/kwh
thnx

#2
11-04-07, 06:49 AM
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Join Date: Sep 2002
Location: welland ontario
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Watts is watts. Doesn't matter if you run 120 or 240 volts.
To calculate the cost multiply the watts times the hours, divide by 1000 to get kilowatt hour run get usage and then multiply that time your cost.

For your lamp run for 12 hours a day for 7 days at \$.053 per KWh.
400 x 12 x 7 /1000 x \$.053 = \$1.78 per week

#3
11-04-07, 06:51 AM
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Cost is wattage multiplied by time used (in hours) divided by 1000. This is kilowatt hours, the unit on which you're billed. Changing the voltage will not make a difference, the wattage doesn't change.

#4
11-04-07, 06:57 AM
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Join Date: Jun 2006
Location: usa
Posts: 274
Originally Posted by mapleleefs
how do I figure out how much it costs to run a fixture? I sort of remember a formula from highschool but don't know what it is. I have a barn light which is 400 watts but don't know how many amps. Is it cheaper to switch the light to run on 220 volts vs 120? I pay 5.3 cents/kwh
thnx

A 400 watt bulb uses .4kw (400/1000) for every hour that the light is burning.
If your electricity costs 5.3 cents per KW, it costs you 2.16 cents per hour to burn the light.

Think of a kilowatt of electricity as being (1) 1000 watt bulb burning continuously for 1 hour equals 1 Kilowatt/hour (kwh).

...Or...

(10) 100 watt bulbs burning continuously for 1 hour equals 1 kwh.

...or...

(1) 2000 watt bulb burning continuously for 1/2 hour equals 1 kwh.

A kwh is a fixed quantity of energy.....1000 watts continuous for 1 hour.
It can be divided any way you choose.

steve

#5
11-04-07, 07:58 AM
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Just curious, what does hydro have to do with your question?

#6
11-04-07, 08:42 AM
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Location: WI/MN
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I'm inferring that hydro means the OP is not in the US and that's the term used in their home or that's the way the site's software translated it for us if the OP isn't using the English language.

#7
11-04-07, 02:40 PM
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Join Date: Jan 2007
Location: Des Moines, IA
Posts: 1,127
Originally Posted by mitch17
Changing the voltage will not make a difference, the wattage doesn't change.

Hmmmm... if the bulb says 400W 120V doesn't that mean it consumes 400W only at that nominal voltage? In other words: If you take a normal (100W,120V) light bulb and somehow drive it with 150V, it's going to become BRIGHTER and consume more power. This is all ignoring the fact that the bulb may not even last very long before burning itself out.

Here's what John Nelson put it, in this thread a while ago:

A 30-watt device has no ability to keep the power consumption at 30 watts. It's not that smart. It merely presents a constant load, and a 30-watt device only remains a 30-watt device if the supply voltage remains the same. If the voltage drops, that 30-watt device suddenly becomes a 25-watt device.
One thing I'm not sure about is what kind of circuitry might be in a fixture for this high intensity bulb. But I certainly wouldn't just arbitrarily double the voltage for a light bulb. It will certainly make a difference -- you'll be in the dark very quickly!

core

#8
11-04-07, 03:01 PM
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Core - you are certainly correct here. I made the assumption we were talking about a device capable of both 110 and 220 volt usage or a different device for each still using 400 watts. In my assumed example, the device with double the voltage would only draw half the current and keep the wattage the same.

#9
11-04-07, 03:31 PM
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Join Date: Sep 2002
Location: welland ontario
Posts: 6,691
Originally Posted by ray2047
Just curious, what does hydro have to do with your question?
In Ontario all electricity is referred to as Hydro. Almost all electric suppliers are XXXXX Hydro such as Welland Hydro or Hydro One(formerly Ontario Hydro).

#10
11-04-07, 03:39 PM
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Join Date: Jan 2007
Location: Des Moines, IA
Posts: 1,127
Ah, mystery solved. The nick 'mapleleefs' sure does scream 'Canada' to me.

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