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Comment by asolidtime1 | Hacker News Reader

>> 1. Always sad for me to know how much popular are wireless chargers, wasting 47% more energy aprox for charging the same as a wired charger.

Sure, but compared to everything else we use, smartphones use almost no energy. The one I'm typing this on has a battery capacity of 12 wh; if you have a resistive electric water heater, standing in a hot shower during the winter for an extra second would offset half of that.

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This nerd sniped me and I had to do the math to confirm, but you're right, at least depending on where you get your estimates and regional power costs. The energy equivalent between a cell phone and shower time is on the order of seconds.

My phone's battery is 4385 mAh @3.7V, or 0.016 kWh, and my power costs $0.1252/kWh, or about $0.002 per phone charge. Based on some super surface-level estimates from googling, a typical shower is about 2 gallon/min, and the cost to heat water is about $0.01-0.02 per gallon, meaning for me it's actually about 4 seconds of hot water per phone charge.

And the parent comment said “47% wasted power … extra second … would offset half of that” and 47% of four seconds is about two, half of that is one second, so I’d say that was shockingly accurate, wow!

Yeah, the math I did was for heating water by 50 kelvins for a 9 l/min showerhead, which in hindsight was probably overestimating it. It'd make sense if the actual answer for most people was 2-4 seconds

Ouch! I already feel bad about shaving in the shower! That is an evocative way to put it.

This is the one less eco-friendly thing I'm not letting go of. Hot showers are amazing.

Did see an interesting thing recently about mist showers. You run them hotter than a normal shower, but they also use significantly less water, and therefore energy. That's always something to consider.

But the lower amount of water flowing will make it harder to remove soap suds from the hair, leading to longer shower times unless you like dandruff :) for me that's the longest part of showering.

Shave your head, easy-peasy.

Ice-cold showers are also amazing. And healthy!

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