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xkcd #3038: Uncanceled Units
(xkcd.com)
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this post was submitted on 15 Jan 2025
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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.
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.