Wireless phone charging energy waste vs EV energy usage - fun random comparisons!

[gsmith123]

Apparently in the EU there is a mandated warning for phones that wireless charging is less energy efficient.

This got me thinking - yes, wireless charging certainly is less efficient (no debate there), but does a phone even use enough energy for this to be at all meaningful in my overall energy usage? How does it compare to my car's usage?

My intuition is phone charging is completely negligible relative to my car, but lets make some comparisons for fun.

Phone Energy Usage

Phone batteries are in the 10-20 watt*hour range. This source claims wireless charging takes about 50% more energy, while this one claims a more modest drop in efficiency. Lets assume a full 0-100% phone charge on wireless takes 6 watt*hours more than wired.

Car Efficiency Estimates

Lets assume a Tesla consumes 280 watt*hours per mile. I know this varies hugely by weather, speed, vehicle, etc.

Putting it all together...

A year of wireless charging my phone, assuming on average 100% of the battery is consumed per day (which is close for me), wastes 2.2 kWh. In car terms, that's only about 8 miles of driving (or 0.04% of my total mileage from the past year! ha!).

So... I guess it is pretty negligible for me. One fun drive around the mountains wastes dramatically more energy.

What about for the whole iPhone population vs the whole Tesla fleet?

This get a lot closer.

There's about 5 million Tesla's driving about 10k miles/year. Total consumption is about 14 trillion watt*hours.

There's about 1.5 billion (!) iPhones. Lets assume that half if all charging is wireless (that feels high but I'm completely guessing here). Total waste from wireless charging comes in at about 1.6 trillion watt*hours.

That feels a lot less negligible, thanks to the absurdly large number of iPhones and modest number of EVs.

 

[dakhlkt22]

Does the Tesla charging pad draw any power if there isn't a wireless device on it that does a handshake with the car and requests power?

 

[Watts_Up]

@gsmith123 I think that some phones can be scheduled when at home to be charged only during off peak hours, if this can make you less guilty.

 

[Watts_Up]

Does the Tesla charging pad draw any power if there isn't a wireless device on it that does a handshake with the car and requests power?

Must be in stand by mode, so very limited energy consumption.

 

[father_of_6]

50% waste is a lot, even if it's 50% of a small amount. As you've shown, when billions of phones waste 50% of their energy, it adds up pretty quickly. As far as I'm concerned, wireless charging should go away if it's that wasteful. It's just not important enough for that much waste.

 

[father_of_6]

And as far as the Tesla wireless charging pad, it'd be nice to have the option to disable it.

 

[Watts_Up]

Maybe we sould also talk about the efficiency concern regarding the future wireless EV charging
which seems to be a very practical solution for urban charging by avoiding the use of cumbersome cables
along street walkways (in particular for blind or low vision pedestrians) and lower vandalism risks.

Wireless Tesla EV charging might have roadmap with German firm

Tesla's apparent acquisition of a company working on wireless industrial charging might actually tie in with Tesla's tease of wireless EV charging—and be a necessary hurdle for robotaxis.

www.greencarreports.com

 

[dakhlkt22]

Maybe we could talk about the efficiency concern about the future of wireless EV charging
which seems to be a very practical solution for urban charging by avoiding the use
of cumbersome cables in the street and lower the vandalism risk.

Wireless Tesla EV charging might have roadmap with German firm

Tesla's apparent acquisition of a company working on wireless industrial charging might actually tie in with Tesla's tease of wireless EV charging—and be a necessary hurdle for robotaxis.

www.greencarreports.com

With those kinds of efficiency losses from wireless charging, it would make sense to pay for bright lighting in charging locations (to deter thieves and vandals), security cameras, loud alarms, and other security measures before switching to less efficient wireless charging.

 

[Watts_Up]

With those kinds of efficiency losses from wireless charging, it would make sense to pay
for bright lighting in charging locations (to deter thieves and vandals), security cameras,
loud alarms, and other security measures before switching to less efficient wireless charging.

In fact magnetic resonance used for wireless electric vehicle charging is quite efficient:

Revolutionizing Electric Vehicles: Wireless Charging Technology

Wireless charging technology for electric vehicles (EVs) is an emerging innovation set to transform the way we charge our cars.

www.linkedin.com

Inductive vs. Resonant Charging Efficiency​

​

Inductive charging systems typically have an efficiency rate ranging from 85% to 90%,​

while resonant charging systems can achieve efficiency rates up to 95% or even higher.​

​

The increased efficiency of resonant charging systems can be attributed to their ability​

to transfer power over a greater distance and with more precise alignment between​

the transmitter and receiver coils. This allows for higher power transfer rates,​

which ultimately translates to faster charging times for EVs.​

 

[dakhlkt22]

In fact magnetic resonance used for wireless electric vehicle charging is quite efficient:

Revolutionizing Electric Vehicles: Wireless Charging Technology

Wireless charging technology for electric vehicles (EVs) is an emerging innovation set to transform the way we charge our cars.

www.linkedin.com

Inductive vs. Resonant Charging Efficiency​

​

Inductive charging systems typically have an efficiency rate ranging from 85% to 90%,​

while resonant charging systems can achieve efficiency rates up to 95% or even higher.​

​

The increased efficiency of resonant charging systems can be attributed to their ability​

to transfer power over a greater distance and with more precise alignment between​

the transmitter and receiver coils. This allows for higher power transfer rates,​

which ultimately translates to faster charging times for EVs.​

There's a pretty big gap between the source that the OP cited stating wireless (inductive?) charging requires 50% more energy and your link that suggests efficiency of inductive is 85-90% and resonant is even better.

 

[Watts_Up]

There's a pretty big gap between the source that the OP cited stating wireless (inductive?) charging
requires 50% more energy and your link that suggests efficiency of inductive is 85-90% and resonant is even better.

This academic publication seems to be a little bit more credible:

Design Methodology and Circuit Analysis of Wireless Power Transfer Systems Applied to Electric Vehicles Wireless Chargers
Published: 1 May 2023

5. Conclusions​

The literature extensively discusses the magnetic resonant wireless system,
but determining the optimal pad parameters for efficient power transfer remains a significant challenge.

This paper presents a design approach for a series–series WPT system to transfer 3.7 kW power at a frequency of 85 kHz,
which can be applied to various power levels.

The magnetic design developed through this approach is analyzed and simulated.
The simulation results reveal that the system can achieve high efficiency of up to 90.02%
while preventing the occurrence of the bifurcation phenomenon.​

 

[gsmith123]

There's a pretty big gap between the source that the OP cited stating wireless (inductive?) charging requires 50% more energy and your link that suggests efficiency of inductive is 85-90% and resonant is even better.

I welcome any better sources! I only spent a few minutes searching around.

Also, I assume there may be a fair bit of variability for phones based on the quality of charger, the alignment of the phone and charger, if there's a case, maybe how fast it chargers, etc. I wonder if Apple's MagSafe that keeps everything lined up has a notable improvement on efficiency as well.

 

[jsmay311]

There's a pretty big gap between the source that the OP cited stating wireless (inductive?) charging requires 50% more energy and your link that suggests efficiency of inductive is 85-90% and resonant is even better.

Yeah... phone charging ≠ car charging.

I wonder if Apple's MagSafe that keeps everything lined up has a notable improvement on efficiency as well.

I'm surprised how hard it is to find good data/sources on this, but this article (from a not completely unbiased source) says Qi charging can lose up to 20% of its charging power from coil misalignment and Magsafe can eliminate that source of loss.