Why do we still confuse KW and KWH?

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Aeronautics has unfortunately remained stubbornly stuck in imperial-land. This has created a few problems with space hardware when units were substituted without proper conversion - the Hubble space telescope mirror comes to mind.
 
css28 said:
If megajoules were the currency of choice I suspect people would be far more comfortable with it. Example; My battery holds 108 MJ when fully charged. My car consumes 14.8 MJ/hr when I'm traveling at 60 mph.
Yep.

Fwiw though, I'm under the impression that Aussies use watt for power. They appear to have internalized the conversion ... somehow. I'm guessing they do not speak in seconds :)
It would be interesting to know how they calculate the time it takes to e.g add 100 MJ to an EV at 50 kW.

Anyway, while Americans are struggling with kWh, I keen for the day when the oh so cumbersome babylonian relic is discarded and we move to a base 10 system for time
 
Titanium48 said:
Aeronautics has unfortunately remained stubbornly stuck in imperial-land. This has created a few problems with space hardware when units were substituted without proper conversion - the Hubble space telescope mirror comes to mind.
Only the imperials would use the same word for a unit of volume AND a unit of weight. Not to mention the insanity of the pound meaning either weight or mass.
 
Pound only refers to mass in the vernacular. The technical imperial unit for mass is the 'slug', although I don't remember ever hearing the term used. It seems like anyone educated enough to know that uses the metric system.
 
SageBrush said:
...I'm always amused by home heating and cooling conventions in Btu. The actual unit being measured is Btu/hour....

This use of BTU is one of the reasons it finally dawned on me that the general public probably wasn't going to bother with the distinction between kW and kWh. For them it's just a way of saying "how big". How "big" is the battery, how "big" is the charger. One unit to rule them all. :lol:
 
Nubo said:
SageBrush said:
...I'm always amused by home heating and cooling conventions in Btu. The actual unit being measured is Btu/hour....

This use of BTU is one of the reasons it finally dawned on me that the general public probably wasn't going to bother with the distinction between kW and kWh. For them it's just a way of saying "how big". How "big" is the battery, how "big" is the charger. One unit to rule them all. :lol:

This isn't entirely incorrect. If a device outputs power at a fixed average or maximum rate, then using that rate as a per hour total doesn't really change comparisons among similar devices. As long as you stay in the same unit of measure, the numbers stay the same, relative to each other. If furnaces, say, were sold in categories like BTU/Hour, BTU/Half hour, etc, then it would get dicey, but a 35k BTU furnace is the same as a 35k BTU/Hour furnace, so the number works for comparison, even if technically incorrect.
 
LeftieBiker said:
Nubo said:
SageBrush said:
...I'm always amused by home heating and cooling conventions in Btu. The actual unit being measured is Btu/hour....

This use of BTU is one of the reasons it finally dawned on me that the general public probably wasn't going to bother with the distinction between kW and kWh. For them it's just a way of saying "how big". How "big" is the battery, how "big" is the charger. One unit to rule them all. :lol:

This isn't entirely incorrect. If a device outputs power at a fixed average or maximum rate, then using that rate as a per hour total doesn't really change comparisons among similar devices. As long as you stay in the same unit of measure, the numbers stay the same, relative to each other. If furnaces, say, were sold in categories like BTU/Hour, BTU/Half hour, etc, then it would get dicey, but a 35k BTU furnace is the same as a 35k BTU/Hour furnace, so the number works for comparison, even if technically incorrect.

Yeah, that's what I mean. In terms of EVs, I'm saying the public's main concern is the "bigness" of whatever they're talking about. They're going to use the term kW for both batteries and charging, without a care for the underlying meaning. The context takes care of it. When talking batteries you know it's energy storage, when talking charging you know it's energy rate. The public says "just tell me how big". As with lay useage of "BTU", the conceptualization of rated or non-rated will be moved from the unit itself, to the context and the actual unit definition will be largely unknown because comparison is the only concern. What percentage of the population actually knows what a BTU is or can internalize the amount of heat it represents? They just know they had a 5000 BTU window box and it didn't cool for **** so they got a 10,000 BTU one next time.
 
LeftieBiker said:
Nubo said:
SageBrush said:
...I'm always amused by home heating and cooling conventions in Btu. The actual unit being measured is Btu/hour....

This use of BTU is one of the reasons it finally dawned on me that the general public probably wasn't going to bother with the distinction between kW and kWh. For them it's just a way of saying "how big". How "big" is the battery, how "big" is the charger. One unit to rule them all. :lol:

This isn't entirely incorrect. If a device outputs power at a fixed average or maximum rate, then using that rate as a per hour total doesn't really change comparisons among similar devices. As long as you stay in the same unit of measure, the numbers stay the same, relative to each other. If furnaces, say, were sold in categories like BTU/Hour, BTU/Half hour, etc, then it would get dicey, but a 35k BTU furnace is the same as a 35k BTU/Hour furnace, so the number works for comparison, even if technically incorrect.
Lets say someone wants to know how much it will cost to run their new fangled Btu burner. They know it is 35k Btu.

Next step ?

---
As for your argument, my Tesla is 78 but it can be 76
 
Lets say someone wants to know how much it will cost to run their new fangled Btu burner. They know it is 35k Btu.

Next step ?

Flow rate of whatever fuel is used, and efficiency rating. As the parameters expand, the simple comparisons break down. There are, however, those stickers on new energy-consuming appliances that give the cost per year for a certain assumed energy cost, plus the efficiency rating, so those calculations aren't needed by the consumer.
 
No one is actually confused. This is just a conversation on a message board. Not the owners manual, not an operating manual, not a physics theses, not wiki, not even a general knowledge base. Simple slip of the keyboard makes way too big a deal of it. For those that are always careful and deliberate to get this right perfectly every time I commend you. For the rest... let it go.
 
smkettner said:
No one is actually confused.
...
Simple slip of the keyboard makes way too big a deal of it. For those that are always careful and deliberate to get this right perfectly every time I commend you. For the rest... let it go.
Sometimes, it's not a slip of the keyboard. Sometimes, a person keeps getting it wrong over and over. This guy is an example: http://mynissanleaf.com/viewtopic.php?p=389319#p389319. He was not just making typos. He didn't know what he was talking about. Read his further replies in that thread like
" A 40w light bulb is not 40w (that would mean it burns out after 1hr) its a 40 wh light bulb"
" A 3000w genny is actually a 3000wh genny"
"a 40w bulb is not 40watts. that would mean the bulb can only work for 1 hour. your average "cheap" incandescent 40w bulb is actually a 60,000w bulb (40watts times estimated lifespan of 1500 hours)

the RATE it consumes power is 40 watts per hour." UGH!

How about Reeler that I referred to at https://www.mynissanleaf.com/viewtopic.php?p=564743#p564743? What's surprising and scary is his background and "experience" with EVs: https://www.mynissanleaf.com/viewtopic.php?p=565245#p565245.

There are a few folks who fairly often get it wrong, say 50% of the time, not 80 to 100% of the time. For them, I think it's a lack of understanding and not a slip up either.
 
SageBrush said:
LeftieBiker said:
Lets say someone wants to know how much it will cost to run their new fangled Btu burner. They know it is 35k Btu.

Next step ?

Flow rate of whatever fuel is used
Indeed. For you it is 35k Btu. :lol:

You may want to double-check yourself before you ROTFL. Two oil furnaces can have the same flow rate and both different efficiencies and thus different fuel costs. They can even have two different BTU ratings. I don't see how that couldn't also be true of gas furnaces with differing efficiencies.
 
cwerdna said:
martyscholes said:
I just read a thread where a poster conflated KW and KWH. That seems to be a regular mistake, despite EVs being more common than ever. What does it take to stop the confusion? The two really are a different as horsepower and a gallon of gasoline.
...
What does it take to get this right? Am I just too pedantic?
It drives me nuts. It happens here, on other EV boards and on various EV FB groups. No on the last question.

I usually step in to correct or to seek clarification. Unfortunately, sometimes (often ignorant) folks will attack me for it. :roll:

People got really pissed off and annoyed at the cluster#$$% I pointed to at https://mynissanleaf.com/viewtopic.php?p=564743#p564743. What's scary and surprising is what Randy pointed out at https://mynissanleaf.com/viewtopic.php?p=565245#p565245. :shock:

+1 but that isn't even the most frustrating part. Correct someone and they become VERY defensive with all kinds of BS reasons as to why its not important, that everyone knows what you mean, You just being an Ahole, etc.
 
Flyct said:
cwerdna said:
martyscholes said:
I just read a thread where a poster conflated KW and KWH. That seems to be a regular mistake, despite EVs being more common than ever. What does it take to stop the confusion? The two really are a different as horsepower and a gallon of gasoline.
...
What does it take to get this right? Am I just too pedantic?
It drives me nuts. It happens here, on other EV boards and on various EV FB groups. No on the last question.

I usually step in to correct or to seek clarification. Unfortunately, sometimes (often ignorant) folks will attack me for it. :roll:

People got really pissed off and annoyed at the cluster#$$% I pointed to at https://mynissanleaf.com/viewtopic.php?p=564743#p564743. What's scary and surprising is what Randy pointed out at https://mynissanleaf.com/viewtopic.php?p=565245#p565245. :shock:

Your ;( overreacting. Or is it you’re overreacting? Calling folks ignorant doesn’t help.

This is another example of how language is perceived. What else would you call them but ignorant when the error is pointed out and they still refuse to correct their mistake? They simply do not know any better.

Problem is society equates ignorant and stupid as synonyms which is far far far from correct.
 
This issue is really one of non-importance... Someone who uses the wrong terminology is either unaware or uninterested in the subtle differences. For example, how many people use the term of acceleration as an increase speed (in meters per second.. per second)?

If you correct a poster's mistake, you either make him feel demeaned and apologetic, or are wasting your keyboard strokes because they couldn't care less.. Some people are on the wavelength of my "windy, turny, thingy is broken". I actually asked a person last week "how is your gas mileage? How much fuel do you use?". Their response was.. "Depends on how far I drive." That was the end of the conversation.

Since this is a public forum, I think that technophiles should let all posts lay as they may, and write instructional messages only when the poster asks a question.

Although terms may have importance in scientific circles, the communication of ideas on this site is not affected if someone talks about having a "40KW battery", or like to plug their level II "charger" into the car. After all, we are all here to share our amazing experiences and news updates of driving a Nissan Leaf--- By joining this site, we are not signing up to be given scientific courses....
 
I am the OP. This has been a good discussion. I took away a few things from the discussion so far.
  • I used the wrong casing for hour, which is lowercase h, not capital H
  • Communicating the right things matters, at least a little
  • But it is not the end of the world if people confuse KW and KWh
  • Correcting people should be done gently since people generally are not receptive
  • KW does not intuitively sound like a rate unit (i.e. KW does not sound like it has time in the divisor), leading to confusion
 
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