Can i use 20W USB-C Power Adapter to charge my macbook air

Given the usage you described, you should find the 20W power supply more than sufficient.

DO make sure to continue using the “charge cable” which shipped w/ your laptop to ensure that the full wattage of the 20W adaptor is delivered.

(Not all “USB-C” cables are equal)

Woodmeister50:

While not disputing your statement, may I inquire as to it’s basis?

My own basis is the quantified power draw of an “every available option” 2017, 4 TB port, touchbar, 15.4” Retina MBP (Model A1707) which shipped with an 87W power supply.

I use a USB-C VA meter.

It consumes less than 20W while running normal “light” business apps and a browser; and still charges the battery (albeit slowly) using an 18W Apple power adaptor (A1720)

The 18W adaptor indeed can’t keep up with more “power hungry” tasks and the MBP battery will slowly discharge until the task is completed.

However, this has never been a limitation in actual stand-alone field use.

The truly “hungry” power consumption comes upon return to in the “office” when driving the dual 5K LG Thunderbolt 27” 5k displays; but in that configuration, the displays are proving all needed power.

The Apple 20W power adaptor will work just fine and help reduce your carry-on “shoulder load.”

I was. using the 30 watt stock charger through a power passing

hub. It "stole" 15 watts for its own purposes leaving 15 watts

for the M1 MacBook Air. It would run fine but would not charge while

running and depending on what I was doing, the battery would

take over and start discharging because there was not enough

power to both charge the battery and run the computer. Another

5 watts would have still left things marginal. Had to get the 81 watt

power block to resolve this which now gives 45 watts to charge and

run the computer.

Also, FWIW, the power draw is not "steady state" and varies dramatically

depending on what sort of processes are running. If you spin up all the CPU

cores or crank up the GPU, power will go up quite a bit, which is not unusual

if streaming video content, i.e. YouTube or such.

While a 20 watt charger may very slowly charge your MacBook Air

when it is turned off, It will not be enough to charge it while in

use and as a matter of fact, depending on the system load, the

battery may actually discharge.

Thank you.