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Comment by iSnow | Hacker News Reader

Not great, but better than I personally expected: "Inductive charging is not as efficient as direct charging [...] An analysis of energy use found that charging a Pixel 4 from 0 to 100 percent on a classic cable used 14.26 Wh (watt-hours), while doing so with a wireless charger took 21.01 Wh, a 47 percent increase. "

https://en.wikipedia.org/wiki/Inductive_charging

Of course problems like heating up the battery and the huge amount of power needed if everyone does it remain.

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"900 million active iphones in use" - CFO Luca Maestri

14.26 Wh * 900000000 * 365 (days) = 4684 GWh/yr

46% = 2154 GWh/yr wasted energy

That's about the total energy output of Madagascar with a population of 27 million people.

There's a lot of reasons why the above numbers are wrong but I just wanted to highlight that at current efficiency, there would be a lot of wasted energy. :)

Thats about the energy demand of a single small aluminium smelter

not exactly a lot of energy in the big scheme of things

Yeah, it's not so much efficiency.. phones don't have that big batteries anyways.

I would be more concerned about charging speed and heating.

Inefficiency implies heating :)

And wow, do I love charging my phone using my laptops USB-C charger.. it's just so fast!

I don't really see the appeal of wireless charging. Faster direct charging would be a bigger win, IMO.

I did some maths (which maybe some should double check), but for an iPhone with a 12 wh battery. Doing a complete charge cycle everyday would consume an extra 5.6kwh over a year! Far more than I expected.

or $0.70 per year at current energy prices.

Germany: hold my beer! 1.78€ or $2.09

But thats not point here. Everyone is talking about the climate change and then we want to charge millions or billions of phones with ~50% extra power?

Good idea!

In absolute terms it's nothing though. An average household uses 4000 kWh of electricity in the UK (less than half of the average us household), so saving the 5kWh on 4 phones is a 0.5% saving, which is roughly equivalent to running your home boiler for 10 minutes per year. Turning off your thermostat for one evening would have the equivalent impact of not using a wireless charger for a century.

> In absolute terms it's nothing though.

Symbols can hold power though.

Do we not have enough symbols? Plastic bags, domestic recycling, plastic straws are all strong "symbols" and yet we're still fighting about a couple of kWh rather than making any meaningful change.

Sure, as long as the electricity doesn't come from fossil fuels. Why not?

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