Mac Charging Reality Check

The problem

Why sustained workloads expose an undersized charger

Ordinary work — mail, browsing, documents — draws so little power that almost any charger keeps up, and a weak one goes unnoticed for years. Local AI is different. Ollama and oMLX push the GPU and memory bandwidth continuously, which is close to the highest sustained power draw an Apple silicon chip can produce. Higher than compiling. Higher than exporting video.

Hot, loud, and still slow

Fans at maximum but tokens crawl.

When the power budget runs short, macOS throttles the chip to fit inside what the adapter can supply. You paid for a Max chip and are running it like a base model.

“Charging” while the battery drops

The menu bar says charging. The percentage falls anyway.

macOS shows “Charging” whenever an adapter is attached. It does not mean you are gaining charge. If the machine draws more than the adapter supplies, the difference comes out of the battery.

Never gets past 50%

Plugged in all day, still stuck at half.

The battery only gains ground in the gaps between generations. Over weeks it settles into a low band and never climbs out.

Looks completely dead

No keys, no screen, no response — as if it failed.

Drained too far, the Mac writes memory to disk and shuts down. An undersized adapter can't accumulate enough charge to boot, so it stays dark. It isn't broken. Leave it on a proper adapter for 20–30 minutes.

Find your answer

What do you actually need?

Pick your Mac and what you do with it. Both answers matter — the same laptop can need 35 W or 140 W depending on the job.

Your Mac

What you're doing

Peak draw

— W

Minimum adapter

— W

Verdict

Choose above.

Draw figures are typical sustained values for these chips, rounded, and used to rank setups — not a spec sheet. Your own number depends on screen brightness, external displays, and which model you're running. The diagnostic commands further down measure your real machine instead of estimating it.

Cables

The cable sets the current ceiling

Every USB-C cable carries a rating. Above 3 amps a cable must contain a small chip — an e-marker — that tells the charger it can handle more. No chip, no permission, and the charger is required by the standard to stop at 3 A. That is the entire 60 W trap: the charger isn't weak, it's being refused.

Cable	E-marker	Current	Voltage	Cable rating	How to spot it
Basic USB-CBundled with phones, cheap spares	No	3 A	20 V	60 W	Thin, smooth plastic, no printing. If you don't know where it came from, assume this one.
5 A e-markedUSB-PD 3.0	Yes	5 A	20 V	100 W	Usually printed “100W” on the connector or sleeve. Often braided.
240 W e-markedUSB-PD 3.1 EPR	Yes	5 A	48 V	240 W	Printed “240W” or “EPR”. The only kind that can carry 140 W to a Mac.
Apple USB-C Charge CableShips with iPhone and small adapters	Yes	3 A	20 V	60 W	Thin white plastic. Looks identical to the good one at a glance — this catches people constantly.
Apple 240 W Charge CableWoven; ships with 140 W MacBook Pro	Yes	5 A	48 V	240 W	Thick, fabric-woven. If it's woven, it's the good one.
MagSafe 3 cableMagnetic, woven	n/a	5 A	28 V	140 W	Obvious — magnetic flat connector. Needs a 140 W adapter behind it to reach 140 W.

A rating is not a charging rate

The right-hand column is what each cable is rated to carry, not what a Mac will draw through it. No Mac charges at 240 W. Apple's highest charging rate is 140 W, on the 16-inch MacBook Pro; most other models are lower.

240 W is the ceiling defined by USB-PD 3.1, and cables rated for it — including Apple's own 240 W cable and UGREEN's equivalent — exist so the cable is never the constraint. Buying one does not make your Mac charge faster than 140 W; it removes the cable as a reason you are not reaching it.

What each Mac will actually draw

Supplying more than a model's maximum is harmless — it simply is not used. Supplying less is what causes throttling and battery drain under load.

Model	Ships with	Maximum it will draw
MacBook Air 13″	30 W	35 W
MacBook Air 15″	35 W	35 W
MacBook Pro 14″base chip	70 W	96 W
MacBook Pro 14″Pro / Max chip	96 W	96–140 W
MacBook Pro 16″	140 W	140 W

140 W is the highest rate any Mac accepts. Reaching it over USB-C requires PD 3.1 at both ends — a charger that offers the 28 V rail and a cable rated for it. MagSafe reaches the same 140 W and is unaffected by cable choice.

Two Apple cables, one difference

Apple's thin white USB-C cable and Apple's woven 240 W cable are both genuine Apple cables, both e-marked, and both look like “the Apple cable.” One carries 60 W, the other 240 W. Woven means fast. Smooth plastic means 60 W. That single texture check settles most cases.

MagSafe vs USB-C

MagSafe is a shape, not extra power

A common assumption is that MagSafe charges faster. It doesn't — on current MacBook Pros both paths reach the same 140 W. Choose on ergonomics.

	MagSafe 3	USB-C
Maximum power	140 W	140 W
Needs a special cable	The MagSafe cable itself	Yes — 240 W / PD 3.1 rated
Survives a tripped cable	Yes — detaches magnetically	No — the laptop comes with it
Uses up a USB-C port	No	Yes
Works with a third-party charger	Yes, with a 140 W PD 3.1 adapter	Yes
Carries data	No	Yes

Reaching 140 W over USB-C requires a Mac that supports it. MacBook Pro models from the M3 generation onward do; earlier Apple silicon MacBook Pros fast-charge through MagSafe. If your Mac is older and you want the full rate, MagSafe is the path.

Multi-port chargers

Multi-port chargers divide their rated total

Multi-port chargers advertise their total. That total gets divided the moment a second device appears — and on many models it divides even when the second device is a fully charged phone drawing nothing. A typical 100 W three-port charger behaves like this:

What's plugged in	Your Mac gets	Everything else	Result
Mac alone, on the primary port	100 W	—	Full rated power
Mac + anything in the second USB-C port	65 W	30 W	Silently cut by a third
Mac + anything in USB-A	65 W	22.5 W	Same penalty, even for a cable charging nothing

Reading the numbers

This is why the exact wattage matters when you check. 60 W means your cable is the limit. 65 W means the charger is splitting power. They're one watt apart on paper and completely different problems — and 65 W tells you to go look for something plugged into another port.

Power-sharing can also stick. If a charger has divided its output once, it may hold that split until mains power is removed. Unplug it from the wall for 15 seconds — not just from the laptop — before concluding anything.

Four years apart

Why a newer charger of the same size delivers more

Two UGREEN GaN chargers, 2022 and 2026, photographed together. They are close to the same size and shape. The rated totals differ — 100 W against 200 W — but the total is not the number that matters to a laptop. The rails on offer are.

A 200 W and a 100 W UGREEN GaN charger side by side, nearly identical in size

Per port	2022 · CD226 · 100 W	2026 · X764 · 200 W
Primary USB-C	100 W20 V / 5 A	140 W28 V / 5 A
Second USB-C	100 Wshared with the first	100 W20 V / 5 A
Third USB-C	22.5 W	30 W
USB-A	22.5 W	22.5 W
Highest voltage rail	20 V	28 V
Standard	USB-PD 3.0	USB-PD 3.1 (EPR)
Combined output	100 W	200 W

The row that decides it

The 2022 unit has no 28 V rail. Its highest tier is 20 V, and 20 V × 5 A is 100 W. That is a hard ceiling set by the hardware: no cable, no port, and no firmware update can take a MacBook Pro to 140 W through it.

140 W requires 28 V, which arrived with USB-PD 3.1. A charger either offers that rail or it does not. This is why “100 W versus 200 W” understates the difference — the useful comparison is 100 W versus 140 W to a single laptop, and it is a generational change rather than a bigger version of the same thing.

Printed specification against measured output

Both units were measured with Smart Charging. Every figure matched the label, which is the point: the information is accurate and public, printed on the underside of the charger — it is simply never surfaced while you are using the machine.

Charger	Port	Label states	Measured
2026 · 200 W	C1	28.0 V / 5.0 A · 140 W	140 W @ 28 V
2026 · 200 W	C2	20.0 V / 5.0 A · 100 W	100 W @ 20 V
2026 · 200 W	C3	12.0 V / 2.5 A · 30 W	30 W @ 12 V
2022 · 100 W	C1	20.0 V / 5.0 A · 100 W	99 W @ 20 V

2026 · X764 · 200 W

Specification label of the 200 W UGREEN charger

2022 · CD226 · 100 W

Specification label of the 100 W UGREEN charger

Before replacing a charger, read its underside. If the highest listed voltage is 20 V, 100 W is its limit for a laptop no matter what the total says.

Hybrid and travel setups

One charger for a MacBook Pro and a mobile workstation

The case for a 200 W four-port charger is not that any single machine needs 200 W. It is that one device can replace two manufacturer power supplies with different connectors, different voltages and very different weights.

Machine	Supplied adapter	Accepts over USB-C	From the 200 W charger
MacBook Pro 16″M-series Max	140 W · USB-C	140 W	140 W on C1
Dell Precision 768016″ mobile workstation	240 W · 7.4 mm barrel	130 W	130 W on C1

Dell documents 130 W input on the Precision 7680's Thunderbolt 4 ports, alongside the 240 W barrel adapter it ships with. USB-C is a supported second path, not a workaround.

What you carry instead

A 240 W workstation brick weighs roughly 1.5 kg. Add a second adapter for the Mac and the power supplies alone approach the weight of a laptop. A single GaN charger replaces both and fits in a hand.

One mains outlet

Hotel desks, trains and shared workspaces rarely offer two free sockets. Four ports from one plug also charges a phone and a headset without a second adapter.

No ecosystem lock-in

The same charger serves macOS and Windows hardware because USB-PD is a standard, not a vendor feature. Only the cable rating and the port you choose determine what each machine receives.

Where the compromise sits

Both machines at once share the 200 W total, so each settles near 100 W rather than its maximum. Full rate is available to whichever is on the primary port.

Worth knowing before you rely on it

130 W is below the 240 W the Precision ships with. For document work, builds and virtual machines that is comfortable. Under sustained CPU and discrete-GPU load the machine will draw more than USB-C can supply and make up the difference from its battery — the same deficit this site describes for a Mac, on different hardware.

The practical arrangement is the barrel adapter at a fixed desk, and the 200 W charger for travel, where carrying one supply instead of two matters more than peak throughput.

Try it here

Run the analysis in your browser

The engine below is the same set of rules the app applies, ported to JavaScript and running in this page. Select a reading measured on real hardware to see how it responds, or paste your own machine's figures underneath. Nothing is uploaded either way.

Now check your own Mac

One read-only command. It changes nothing and needs no administrator rights.

Step 1 · run this in Terminal

ioreg -rn AppleSmartBattery | tr ',' '\n' | grep -E '"(Watts|AdapterVoltage|Current|CurrentCapacity|Voltage|InstantAmperage|IsCharging|Temperature|MaxCapacity|CycleCount|MaxVoltage|MaxCurrent|ExternalConnected)"'

Step 2 · paste everything it printed here.

Runs entirely in your browser. Nothing is uploaded or stored.

The command only reads sensor values. It changes nothing, needs no administrator rights, and works on any Mac with a battery.

Measure it

Reading the figures yourself

Open Terminal (press ⌘ Space, type Terminal, press Return), paste, press Return. Nothing here changes anything on your Mac — both commands only read.

Plug in properly first

Mac on the charger's primary port. Nothing in the other ports — check physically, including small dongles. Charger plugged directly into the wall, not a hub or extension.

Ask what the adapter is delivering

This is the headline number — what your Mac is actually receiving right now.

Terminal

system_profiler SPPowerDataType | grep -A6 "AC Charger Information"

Ask why it's that number

Current is the cable's ceiling; AdapterVoltage shows which rail you're on. Together they name the culprit.

Terminal

ioreg -rn AppleSmartBattery | tr ',' '\n' | grep -E '"(Watts|Current|AdapterVoltage)"='

What your result means

Watts	Current	Diagnosis	Fix
60	3000	Cable has no e-marker. Capped at 3 A regardless of charger.	Replace the cable. Cheapest fix there is.
65	3250	Charger is splitting power. It thinks a second device is attached.	Empty the other ports, then unplug from the wall for 15 s.
30	3000	You're on the charger's low-priority port, or it's mid-negotiation.	Move to the primary port and re-check after 10 s.
100	5000	Full standard USB-PD. Fine for everything except sustained large-model work.	Nothing, unless you run big models.
140	4990	Full rate. Voltage will read 28000 — that rail only exists on PD 3.1.	Done.

Watching it under load

To see whether you're winning or losing while a model runs, start a generation and watch the battery current. Press Control + C to stop.

Terminal

while :; do ioreg -rn AppleSmartBattery | grep '"InstantAmperage"'; sleep 5; done

A normal number means you're charging. A gigantic one like 18446744073709551394 is how macOS writes a negative value — it means the battery is draining while plugged in. That's the whole problem, visible in one line.

What to buy

What to change, in order of effect

A 240 W / PD 3.1 USB-C cable — around €20

Buy this before anything else, and buy it even if you're sure your cable is fine. It's the cheapest component, the most common failure, and it's required for any speed above 100 W later. Versions with a small wattage display on the connector are worth the few euros more: you see the number without opening Terminal ever again.

Test before buying a charger

With a proper cable, your existing charger may already deliver its full rating. If that's enough for your workload, you're finished and you've spent €20 instead of €100.

A 140 W-capable adapter — only if the test says so

Required for sustained large-model work on Pro and Max chips. Check the fine print for 140 W on a single port and PD 3.1. Many “200 W” chargers cap every individual port at 100 W, which buys you nothing. Apple's own 140 W adapter is the guaranteed-correct option.

Free things to try first

Empty every other port on the charger. Unplug it from the wall for 15 seconds. Move to the primary port. Try your other cable — if two cables give different wattages, the higher one is the better cable. Plug into the wall directly rather than through a hub, monitor, or extension lead. And if you still own the adapter that came with the Mac, that one is correct by definition.

The app

What Smart Charging does

Everything on this page can be derived by hand with ioreg. Doing it continuously, while you work, is what makes it useful. Smart Charging reads the same sensor every few seconds and reports two things that affect you directly: whether your Mac is being throttled by its power supply, and what your current setup is doing to the battery.

Sustained performance

When the supply cannot meet demand, macOS throttles the chip to fit inside it. Seeing the deficit in watts tells you whether a slow model run is the model or the charger.

Battery longevity

An undersized supply forces continuous shallow charge and discharge while the chip runs hot. Heat and cycling are the two mechanisms that age lithium cells; both are tracked.

Identifies the limiting component

A cable cap and a slow port produce similar wattage but need opposite fixes. Reading the voltage rail alongside the current separates them.

Detects change over time

It records the best a charger has offered, so a drop after changing ports, adding a device, or a stuck negotiation is reported rather than absorbed.

Download for macOS Source on GitHub

Requires macOS 14 or later. Apple silicon and Intel.

Also open source

A related tool: Mac App Store screenshots

Building Smart Charging turned up a second problem. Every App Store screenshot generator targets iPhone, iPad and Android. The Mac App Store wants 16:10 landscape at its own four sizes, flattened RGB with no alpha, and it must show your real interface or the listing gets rejected. Nothing covered it, so that got built too.

Every size Apple accepts

1280×800 through 2880×1800, flattened with no alpha channel — the thing that quietly fails an upload.

Five layouts

Text left, text right, centred, full-bleed showcase, and a big-number spotlight. Choosing well is most of what looks professional.

Captures the window for you

Point it at a running app and it finds the window itself, or use screenshots you already have.

No dependencies

One Swift file on CoreGraphics. No npm, no project scaffolding, no network, nothing to install.

Install and run

Three steps. Requires macOS and the Xcode command line tools.

Terminal

git clone https://github.com/bluehawana/appstore-screenshot-forapps
cd appstore-screenshot-forapps
swift makeshots.swift --layouts

Then describe your slides in a small JSON file — image, headline, subhead, layout — and render every size in one pass:

Terminal

swift makeshots.swift screenshots.json

Or grab a single file if you would rather not clone anything:

Terminal

curl -O https://raw.githubusercontent.com/bluehawana/appstore-screenshot-forapps/main/makeshots.swift

Screenshot generator on GitHub

It ships a SKILL.md, so Claude Code and compatible agents can drive it directly — drop the folder into your skills directory and ask for App Store screenshots. MIT licensed.