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Old 11-11-2015, 07:19   #76
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Re: How many kilowatts per day do you use?

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Originally Posted by sailorchic34 View Post
Power is energy per unit of time. Power is watts. Energy is watt-hours
Exactly. And using an energy unit makes it inconvenient to calculate anything useful (unless you're an electrical utility) because it needs to be normalized to a specific period of time.

It's equally valid to say "My continuous power usage is 100 watts" as it is to say "My daily energy usage is 2400 watt hours" but the latter is obfuscated and doesn't give an immediate sense of either the generating capability or the total loads when talking about a self-contained system like a yacht.
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Old 11-11-2015, 07:35   #77
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Re: How many kilowatts per day do you use?

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Exactly. And using an energy unit makes it inconvenient to calculate anything useful (unless you're an electrical utility) because it needs to be normalized to a specific period of time.

It's equally valid to say "My continuous power usage is 100 watts" as it is to say "My daily energy usage is 2400 watt hours" but the latter is obfuscated and doesn't give an immediate sense of either the generating capability or the total loads when talking about a self-contained system like a yacht.
Most boats (or houses or buisnesses) don't have contionous power usage. Most of the devices powered use electiricty intermittently. At anchor, when the fridge kicks on, you may be drawing 200watts but as soon as it stops, the draw may drop to 20watts. As a result, while the average (continous?) power usage may be 100watts, it's entirely possible the actual usage may never be 100watts.

If you are talking about DC power sources (ie: batteries), continous power usage doesn't tell you much about generating capability either without doing some calculations (ie: detemining watt-hr or amp-hr). If you are drawing 100watts continously (average?), that doesn't mean 100watts of solar panels will serve your needs (ignoring efficency issues). You need to estimate how long each day, the panels will produce 100watts (or some lesser wattage). That translates to watt-hr (or since it's more easily measured amp-hrs).
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Old 11-11-2015, 07:58   #78
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Re: How many kilowatts per day do you use?

Watts per hour or watts per day. Is it really all that confusing?
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Old 11-11-2015, 08:09   #79
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Re: How many kilowatts per day do you use?

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Watts per hour or watts per day. Is it really all that confusing?


Yes - you are confusing.
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Old 11-11-2015, 08:09   #80
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Re: How many kilowatts per day do you use?

Valhalla: Yeah, that's why we average it over a day. That's what MOST of the people in this thread understand by the "per day" part of the statement. All but the utterly pedantic anyhow.
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Old 11-11-2015, 08:16   #81
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Re: How many kilowatts per day do you use?

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I think of course you meant to say 6 to 7 kWh per 24 hour period at anchor.
You are quite right Dennis, thank you. The OP asked for power usage and that is Kw - kWh is a useless response.
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Old 11-11-2015, 10:05   #82
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Re: How many kilowatts per day do you use?

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Exactly. And using an energy unit makes it inconvenient to calculate anything useful (unless you're an electrical utility) because it needs to be normalized to a specific period of time.

It's equally valid to say "My continuous power usage is 100 watts" as it is to say "My daily energy usage is 2400 watt hours" but the latter is obfuscated and doesn't give an immediate sense of either the generating capability or the total loads when talking about a self-contained system like a yacht.
Why would the latter sentence be obfuscated? Obviously it has nothing to do with electricity generation capability or total loads.

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Old 11-11-2015, 10:16   #83
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Re: How many kilowatts per day do you use?

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I know this exactly, since I get an itemised electric bill

Around 100KWH a month in summer, which is just over 3 KWH a day. That's as a full time liveaboard.

No heating or air con, (or solar )but I have a hot water tank and pressure water. Most of that usage is probably the hot water tank and my battery charger. ......
Do you leave this on all the time?
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Old 11-11-2015, 10:48   #84
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Re: How many kilowatts per day do you use?

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I'm going to be calculating my energy budget soon so this is of interest to figure out.
Becky,

This talk of watts and kilowatts has my brain split, too.

Here's my energy budget spreadsheet. It's done in amp loads and then amp hours, and used to size a battery bank. The conversion to watts is just linear, but with any given boat electrical system, it doesn't matter the voltage 'cuz the watts consumed by any device regardless of voltage are the same, so in my simple mind, why bother with the conversion to watts at all, since our electrical loads are, for example, 12V NOMINAL and so are your batteries, which are "sold" to you based on an amp hour rating.

With all due respect to the Scotsman, Mr. Watt, I stick with Monsieur Ampere.

The All-Important Energy Budget:
Energy Budget
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Old 11-11-2015, 11:03   #85
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Re: How many kilowatts per day do you use?

Couple questions for StuM,

1)* Homer is eating 4 apples per second, how many apples did Homer eat?

2)* Homer eats 4 oranges, how many oranges did Homer eat?


You can NEVER have a bag of watts, you can however have a bag of doughnuts...
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Old 11-11-2015, 11:32   #86
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Re: How many kilowatts per day do you use?

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Couple questions for StuM,

1)* Homer is eating 4 apples per second, how many apples did Homer eat?

2)* Homer eats 4 oranges, how many oranges did Homer eat?


You can NEVER have a bag of watts, you can however have a bag of doughnuts...
Here's how I view the argument of how to state what most of us convert to the acceptable construct in our heads without constant derailment of an op's question.


How I see math word problems: If you have 4 pencils and 7 apples, how many pancakes will fit on the roof? Purple, because aliens don't wear hats
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Old 11-11-2015, 11:39   #87
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Re: How many kilowatts per day do you use?

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.................................................. ....................Purple, because aliens don't wear hats
Oh, yes, they do, two hats PER head, too.

Or is that two heads per hat???
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Old 11-11-2015, 11:44   #88
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Re: How many kilowatts per day do you use?

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Originally Posted by newhaul View Post
Here's how I view the argument of how to state what most of us convert to the acceptable construct in our heads without constant derailment of an op's question.


How I see math word problems: If you have 4 pencils and 7 apples, how many pancakes will fit on the roof? Purple, because aliens don't wear hats
I disagree. Octangle pocker dots.
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Old 11-11-2015, 12:09   #89
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Re: How many kilowatts per day do you use?

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Oh, yes, they do, two hats PER head, too.

Or is that two heads per hat???
I don't it would bend my anteni and hinder reception of when the mother ship will return
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Old 11-11-2015, 12:52   #90
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Re: How many kilowatts per day do you use?

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Here's how I view the argument of how to state what most of us convert to the acceptable construct in our heads without constant derailment of an op's question.


How I see math word problems: If you have 4 pencils and 7 apples, how many pancakes will fit on the roof? Purple, because aliens don't wear hats
how many pancakes will fit on the roof? 41
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