

10112015, 10:42

#46

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Re: How many kilowatts per day do you use?
If you measure in Kw rather than watts then you need to seriously look at usage. 4800w is average for me
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10112015, 10:49

#47

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Join Date: May 2011
Location: Sea of Cortez and the U.P. of Michigan
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Posts: 770

Re: How many kilowatts per day do you use?
Quote:
Originally Posted by a64pilot
... I do not need to say I consumed 100 Watts per hour for ten hours?

Not only do you not need to say it, you should not say it.
You should be saying something like "I consumed 100 Watthours (Wh) over ten hours" instead.
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10112015, 11:03

#48

Moderator
Join Date: Sep 2006
Posts: 4,220

Re: How many kilowatts per day do you use?
If you connect 1V to a 1 Ohm resistor, 1 Amp will flow, and the resistor will dissipate 1W. Not 1W per day, not 1W per any amount of time. 1W is an instantaneous measurement of power, like Horsepower. "1W per day" does mean something (a rate of change), but it does not mean energy.
That 1 Ohm resistor, if it dissipates 1W continuously, will consume 1 Wh per hour, or 24 Wh/day, or 168 Wh/week. Or 1 Wattsecond per second.
A sailing analogy is:
Watts = speed, Watt Hours = distance.
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10112015, 11:25

#49

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Join Date: Oct 2013
Location: Albany Ga.
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Re: How many kilowatts per day do you use?
Quote:
Originally Posted by roland stockham
If you measure in Kw rather than watts then you need to seriously look at usage. 4800w is average for me

Although it was not stated, I took it to mean living off of shore power, OP did say Winter and Summer. He didn't stipulate per day or per month, so of course we have been all over the place with our answers, but if I'm tied into shore power, I'm a whole lot less conservative with power useage.



10112015, 12:04

#50

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Join Date: Feb 2011
Location: SF Bay Area
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Re: How many kilowatts per day do you use?
[QUOTE=Dennis.G;1959025]So when you say "1 kW per day" you are saying "1000 Joules per second per day". Does not make any sense.
Nope, I'm saying 1KW used per day, which equals 3,600,000 joules, same as 1kWh.
A watt is also an energy value.
When you say you use 1kWh you also don't define at what rate the energy is flowing. Could be 60kw for a single minute or 16.6 watts per minute for an hour.
A kWh is simply 1000 watts consumed for a bill purpose. Heck, you could consume 1kwh at a rate of 1 watt for 1000 hours That would still be 1 kWh on your electric bill and has little bearing on actual energy consumed in an hour or day.
Generally when I say I use 1kw per day, we all pretty much know what I'm taking about, that is I consumed 1000 watts of energy or power per day. Yes I could have said I used 1 kWh per day, but then we would not be having this lovely discussion.
Your welcome.



10112015, 12:20

#51

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Join Date: Feb 2011
Location: SF Bay Area
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Re: How many kilowatts per day do you use?
Quote:
Originally Posted by Paul Elliott
A sailing analogy is:
Watts = speed, Watt Hours = distance.

Nope. Watt is joule per second. wh also uses joules per second but with the duration being one hour.
You could use 60 wh, but all that energy could have happened in a single one second pulse in that hour to give you 216,000 joules/sec or 60wh. It could also be one 60 watt light bulb that uses 60 watts for one hour, also 216,000 joules. So wh is not a distance but a quantity as in watts per hour, well really joules per hour. Glad we're not using ergs.
Are we having fun yet.



10112015, 12:20

#52

Moderator
Join Date: Sep 2006
Posts: 4,220

Re: How many kilowatts per day do you use?
From Wikipedia:
Quote:
The watt (symbol: W) is a derived unit of power in the International System of Units (SI), named after the Scottish engineer James Watt (1736–1819). The unit is defined as joule per second[1] and can be used to express the rate of energy conversion or transfer with respect to time.

Watt is a rate, much like speed.
Watthour is a quantity, much like distance.
Here is a link to the Wikipedia section titled "Confusion of watts, watthours and watts per hour"
https://en.wikipedia.org/wiki/Watt#C...watts_per_hour
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www.sailvalis.com



10112015, 12:32

#53

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Re: How many kilowatts per day do you use?
Quote:
Originally Posted by Paul Elliott

Read that last night..
Watt is a quantity of one joule for one second. it's not a speed of joules.
Wh and kWh are both quantity of energy used over a time period and don't give you the rate it was used at. Same with watts it's not speed but a quantity of joules used.
So lets say we're measuring a laser pulse that uses 1kWh. Well call it my death ray. That one kwh or 3,600,000 joules of energy could be consumed in a single one second pulse and still be 1kwh on your electric bill. So a kwh is not really a distance, but simply a quantity of energy consumed. It does not tell you the rate that it was consumed at.



10112015, 13:05

#54

Senior Cruiser
Join Date: Nov 2013
Location: Port Moresby,Papua New Guinea
Boat: FP Belize Maestro 43
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Re: How many kilowatts per day do you use?
Quote:
Originally Posted by a64pilot
1,000 Watts, is a 1,000 Watts total.
Stating a time defines rate, not total.
I don't know why this confuses, if I said I burned 10 gl of Diesel today everyone would understand. It should be the same if I state I burned 1000 Watts today. I don't need to state I burn 1 gallon per hour and ran for ten hours do I? I do not need to say I consumed 100 Watts per hour for ten hours?

I don't know why it confuses either  but you are definitely confused by it
Watts IS A RATE, not a total. It already contains a time factor just as knots do.
Please see Amps v Amp hours v Amps/Hr
You are making exactly the same mistake as SC.
What you both are missing is the critical, fundamental different between "Actual Consumption" and "Rate of Consumption"
Units of " rate of consumption" (e.g. Power,speed,flow rate) are :
Watts (J/s) or knots (nm/h) or gallons per hour (g/h)
Units of "actual consumption" (e.g. Energy, distance, volume) are:
Watt Hours (Wh) or or nautical miles gallons
So you can't use gallons as an analogy for Watts.
Just as you can't burn "10 gallons per hour in a day" or cover "10 knots per day" , you can't use "10 Watts in a day".
When you confuse these two you end up with things like SC's two statements
1. 1kWd = 86,400,000 Joules. (True)
2. Her daily usage is 1kWd (False)
Her daily usage is not 1kWd which is 24kWh (or 86,400,000 Joules), it is 1kWh (or 36,000,000 Joules).
She overstated her consumption by a factor of 24 (both in kW and initially in Joules) of what she was actuallyusing.
This is a classic example of what happens when you get this wrong.
She put herself up at the top of the biggest consumers on this thread although she is one of the smallest consumers.



10112015, 13:15

#55

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Re: How many kilowatts per day do you use?
Quote:
Originally Posted by sailorchic34
Watt is defined as one joule per second and can be used to express the rate of energy conversion or transfer with respect to time.
If I had said, I used 1000 watts, I would agree that it does not define a time unit.
But I said I used 1kw per day which is 1000 watts in a day. That is exactly the same as saying I used 1kWh in a day. kWh is a lovely unit. But I don't use it much as I have not had in electric bill in well over 10 years.

If you said you used 1000 watts, that DOES define a time unit  you just said so in your definition. 100 Watts is 1000 Joules (units of energy) PER SECOND. Just as 1000 knots is 100 nautical miles (units of distance) PER HOUR.
Every time you use Amps or Watts, just try replacing it with knots. If it still makes sense, then you are using it correctly. Every time you use Amp hours or Watt hours, try replacing it with nautical miles.
"1kw per day which is 1000 watts in a day That is exactly the same as saying I used 1kWh in a day."
"1000 knots per day. That is exactly the same as saying I covered 1000 nautical miles in a day." Surely, even you can see that this one is wrong.



10112015, 13:19

#56

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Re: How many kilowatts per day do you use?
Quote:
Originally Posted by roland stockham
If you measure in Kw rather than watts then you need to seriously look at usage. 4800w is average for me

Yes but 4  800 W over 24 hours is 9,600 Watt to 19,200 Watt hours per day (assuming that is actually 400800 ).
So you are using somewhere between 9.6 and 19.2 kWh per day.



10112015, 13:22

#57

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Re: How many kilowatts per day do you use?
Quote:
Originally Posted by a64pilot
Although it was not stated, I took it to mean living off of shore power, OP did say Winter and Summer. He didn't stipulate per day or per month, so of course we have been all over the place with our answers, but if I'm tied into shore power, I'm a whole lot less conservative with power useage.

The OP did stipulate "per day". See the thread title (but also note Post #2 where he quickly realised his mistake and corrected it to "kilowatt hours per day")



10112015, 13:23

#58

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Join Date: Feb 2011
Location: SF Bay Area
Boat: Islander 34
Posts: 5,026

Re: How many kilowatts per day do you use?
Quote:
Originally Posted by StuM
Her daily usage is not 1kWd which is 24kWh (or 86,400,000 Joules), it is 1kWh (or 36,000,000 Joules).
She overstated her consumption by a factor of 24 (both in kW and initially in Joules) of what she was actually using.
This is a classic example of what happens when you get this wrong.
She put herself up at the top of the biggest consumers on this thread although she is one of the smallest consumers.

StuM, you sweet talking devil you.
Watt is a quantity of one joule for one second. A Kwh is 3,600,000 joules. What we don't know is was that amount of joules used in one second or in ten minutes or in an hour. kwh like watt is a quantity of joules. That's all. Please don't start comparing it to speed and distance or gallons or whatever. So not at all the same.
My kw per day was quite clear that it was 1000 watts per day or 3,600,000 joules, same as 1kWh. Please don't read into it what was not there.



10112015, 13:28

#59

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Re: How many kilowatts per day do you use?



10112015, 13:29

#60

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Join Date: Feb 2011
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Re: How many kilowatts per day do you use?
Quote:
Originally Posted by StuM
If you said you used 1000 watts, that DOES define a time unit  you just said so in your definition. 100 Watts is 1000 Joules (units of energy) PER SECOND. Just as 1000 knots is 100 nautical miles (units of distance) PER HOUR.
Every time you use Amps or Watts, just try replacing it with knots. If it still makes sense, then you are using it correctly. Every time you use Amp hours or Watt hours, try replacing it with nautical miles.
"1kw per day which is 1000 watts in a day That is exactly the same as saying I used 1kWh in a day."
"1000 knots per day. That is exactly the same as saying I covered 1000 nautical miles in a day." Surely, even you can see that this one is wrong.

ROFL, Stu I love it when you use knots and nautical miles to define watts and joules. You might want to check your units BTW. So how far is 10kWh.....
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