For something that doesn't run continuously, like eg. a refrigerator, then an average daily usage is more useful, no? "This product draws 1.5 kW with a duty cycle of 0.08" doesn't really help when comparing efficiencies of potential purchases, you'd need to convert it to electricity consumed in a set period anyway.
this post was submitted on 15 Jan 2025
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No, it's because watts are joules per second, so kWh are (energy / time) * time. Cancelling the units would be expressing the energy directly in joules.
But the XKCD mentions kWh/day specifically, in theory the times can cancel out, leaving you with kW
But instantaneous and average kW are very different, and it would take more time to describe that distinction than to use kWh/day.
My freezer was labeled in max watts, kwh/day, and kwh/year. Because the cumulative watts over time is what I pay for my power bill. That way it's a simple multiplication that tells me how much having that freezer would cost.
Ok that's fair, I kinda glossed over that part. Both are valid interpretations, I think.
Exactly, it's a unit of convenience, not a unit of abstract precision.
Even a unit of "gallons/sqft" could be handy in the right context. If you were trying to design a storage solution for discretely packaged product for example, it could be a figure of merit despite literally factoring out to a unit of length.
Yeah a chest freezer is a good example of a situation where both are useful things to put on the tag
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kWh is already an uncanceled unit, drives me nuts even without adding per day
(Energy / time) * time? fuck you
It's because the times aren't the same. Maybe same unit but different context so they can't be canceled.
It's like saying you work 8 Hours/day (Eight hours per day). Both are units of time, but their context is different and their combination forms a new meaning beyond the units.
1 KWh is using 1KW for one hour. Because of demand pricing the time you use that KW is important. Like in terms of energy grid using a whole ton of power for one minute vs same total over a long time is different and important dispite being the same amount of energy.
Edit: some phrasing
Time cancels out.
I work 8.
Gotta convert time to the same units before canceling: you work 1/3
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Because nobody's used to seeing Joules, you could swap in kJ for kW-seconds but then you probably need to switch base (MJh) to keep it practical, and now people need to do extra math to tell what will be on their power bill
But go ahead and call your power company to get them to list Joules
My power company provides me electricity in kWh, and heating (in the form of hot water) in GJ. And my cold water gets charged in m3.
So they DO know. For a few years, they'd even "helpfully" translate the GJ into kWh, untill it started to piss off people who bought electric heaters and found that those two numbers weren't actually the same in the real world.
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It's also due to social inertia.
Power companies charge by the kWh because their generators are measured in total output wattage and consumers consume at different wattages at different times.
Sure, it would be easier to measure in total joules consumed per period time but it would also be easier to measure with world standard metric units. The pain of changing is harder than staying the same, so muh freedum units.
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There's nothing wrong with kilowatts, it's an SI unit. The problem is hour, which is 3600 seconds, and we have ancient Egyptians to blame for this, who divided the day into 24 hours despite having already developed base-10 numerical system.
Kilowatt per kilosecond, which is 1 megajoule, would work better.
I really don't get the issue with kWh. Things are rated in W and we mostly care about the hours they're powered on. If I wanna figure out how many kWh a PC that needs 300W used in 4 hours, I multiply 300*4. If I wanna know how many joules it used, I have to do 300*4*3600. Only one of those can be done in your head in 3 seconds.
You gotta use an escape character, specifically a backslash ( \ ), when dealing with *s on lemmy.
Otherwise you end up with "stufflike this!"
When it could have been "stuff*like this*!"
ETA: Damn, you're good. Fixed it before I even finished this post!
Damn, I was convinced it was the Babylonians with their base-60 system.
That actually works great.
60 is cleanly divisible by 1, 2, 3, 4, 5, and 6, 10, 12, 15, 20, and 30.
10 is cleanly divisible by 1, 2, and 5.
Yeah Babylon was very clever but also looking at their math and writing makes it clear why they had to have a class of people to do their math and writing
I have no problem remembering what 1 is divisible by.
It would've been better if we had a 6 or 12 based number system
The big reason for 60 over 12 or 6 is the divisibility by 5. That makes it divisible by all numbers through the first 3 primes.
To get it divisible by all the numbers up to the next prime (7), you'd have to go to 420, and the one after that (11) you'd need to go to 27,720, and 13 would require a whopping 360,360.
The problem with base 60 is needing to know and remember instinctively the names, symbols, and relative positioning for 60 digits. Like, I love Babylon, they're underrated for certain, but imagine teaching this to a 5 year old. Imagine doing calculus with this shit. Now remember that their writing impliment was a triangular reed and their written marks were entirely triangles and straight lines.
I knew a 26-letter alphabet by the time I was 2.
Yes, but set to music i assume and not nearly to the level one was expected to understand the ordering of digits.
In base 34: 1…9,a…z,10 it's slightly more than half the digits the babylonians had, and as someone whose career involves a lot of math I don't want to be dealing with at a glance trying to figure out the approximate difference between jl5x and ik8r
As an adult with a college degree in stem I know my digits and their ordering perfectly and without question unless literally trying to trip me up. The alphabet, I know in that specific order and would have to think to start in the middle. I don't want to do series or sequences on that shit and if you do then good for you
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That's 203.7cm for anyone wondering
Assuming US Gallons. With Imperial Gallons, it's 2.447 m
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Going from Watts to BTU's while researching for a solid state multi-power-state TEC cooling solution. I feel this.
My car needs 0.07 square millimeters of fuel on the highway.
square? Damn it uses no volume of fuel at all!
Isn't that crazy efficient? I seem to remember about 0.3mm²?
Way back of you asked Google "38 mpg in mm^-2" it would tell you.
I love that it's the size of the thread of fuel you would consume as you drive down the road.
Edit: oh no, that's about right. It's a diameter of about 0.25 mm. I think that's what I was thinking of.
Not sure. I asked my cat Jeepity.
And they're cursed for a region, you don't define a distance as volume! As I'm typing that, I realise this also defines a distance as a bodypart, ah well
But what temperature is that at? And what is the ambient temperature? And what if the power is not at exactly 120V? And what about if I put a fresh dead hooker in it every day?
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