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Comment by amelius | Hacker News Reader

> Probably they think they can make the jump to a completely wireless phone before any USB-C mandates come in.

What is the efficiency of wireless charging?

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.

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?

"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 see a lot of comments suggesting that Apple want to go fully wireless but it makes no practical sense to me. Their MagSafe charger not only charges far slower (as of now), but it's also huge. It's just not practical to ask someone to carry that around with them or take it when they go travelling.

Also, next time EU will rephrase their law such that every device should really use the same charger (whether wired or wireless).

An interesting point to think about is that MagSafe appears to be about 75% efficient (due to alignment of coils from the magnets), but also the battery size on iPhones tends to be much smaller than competitor phones.

For example, Samsung S21 uses a 4000mAh battery. iPhone 12 Pro uses a 2700mAh battery.

At 75% efficiency, it's effectively like charging a 3600mAh battery.

Both likely get a full charge every day. So, even with less efficient charging, you come out ahead vs. a Samsung device.

That's also assuming efficiency of the actual charging bricks is similar. Apple tends to be known for high quality and efficient charger bricks, so it wouldn't surprise me if that has an impact.

Still, throwing away 25% electricity because "minor convenience" is not such a great idea.

Sure, but let's say efficiency comes up to closer to like 85-90%, which should be achievable. Would you suggest that it's still not worthwhile? You'd never need to worry about damaging your charging port, since everything is now solid-state.

I know a few folks that moved to exclusively wireless charging because they broke the USB port on their phones over the years.

It is terrible, adds heat and is worse for the environment. See any long-term review of the Magsafe wireless external stick-on battery for the iPhone.

I'm not advocating for wireless charging, I'm simply answering the question posed.

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