Compare · Phone vs phone-and-tablet
20W vs 30W: one extra rail changes the job.
A 20W adapter is a phone charger. A 30W adapter adds the 15V and 20V rails, which is what turns it into a tablet and MacBook Air charger as well. That structural difference matters far more than the 10 watts on the label.
Spec sheet, side by side
| 20W | 30W | |
|---|---|---|
| Output profile | 5V/3A, 9V/2.22A | 5V/3A, 9V/3A, 15V/2A, 20V/1.5A |
| Rails above 9V | None | 15V and 20V |
| Ports | 1× USB-C | 1× USB-C (GaN units often fold) |
| Size class | Small cube | Same or smaller in GaN |
| Best-suited devices | iPhone, AirPods, Watch, Kindle | + iPad, iPad Air, Switch handheld, MacBook Air (slow) |
| Fast-charge iPhone | Yes, at full speed | Yes, at full speed |
On an iPhone the two are a tie: the phone peaks around 20–27W and takes what it needs from either. The divergence starts at the iPad, which pulls close to 30W, and continues at the MacBook Air, which shipped with a 30W brick as its baseline.
Where each one wins
20W wins on price bracket and nothing else. It is the cheapest adapter that fast-charges a phone, which makes it the right thing to buy in multiples — one per room, one per bag. If your entire device list is a phone plus earbuds, extra watts sit unused.
30W wins the moment a second device class appears. An iPad Air charges roughly a third faster; a Nintendo Switch in handheld mode is comfortably fed; a MacBook Air will charge from it overnight and hold charge during light work. Crucially, 30W is where GaN took over, so a 30W GaN unit is typically smaller than Apple's 20W brick while doing more. Class detail: 20W adapters and 30W adapters.
Verdict: 30W for almost everyone
Buy 30W. The criteria all point the same way: delivered watts for your device (identical on a phone, meaningfully better on a tablet or laptop), protocol correctness (30W carries the 15V and 20V rails a 20W unit structurally cannot), size (GaN erased the penalty), and headroom for whatever you buy next. The exception is narrow and real: if you are stocking up on cheap spare bricks for phones and earbuds only, 20W is the better watt-per-dollar buy and you should take it. Next steps up are covered in 30W vs 45W; if you're comparing Apple's own bricks, see Apple 30W vs 35W Dual.
- 20W
Apple 20W USB-C Power Adapter
The 20W side of the argument. Full iPhone speed, nothing above the 9V rail.
- Output
- 20W USB-C PD
- Rails
- 5V/3A, 9V/2.22A
- Ports
- 1× USB-C
- 30W
Anker Nano 30W
The 30W side. Folding plug, GaN, smaller than the brick it replaces.
- Output
- 30W USB-C PD
- Ports
- 1× USB-C
- Tech
- GaN
- 2-port
Apple 35W Dual USB-C Compact
The compromise: 35W solo, or roughly half each with two devices attached.
- Output
- 35W total
- Ports
- 2× USB-C
- Shared
- Splits when both used
Not sure which class your devices sit in? Start at what wattage do I need or browse every head-to-head at charger comparisons.
FAQ
Does a 30W charger charge an iPhone faster than a 20W one?
Barely. An iPhone's peak draw is around 20 to 27W and it tapers quickly, so the two land within a couple of minutes of each other to 50%. The 30W advantage shows up on tablets and laptops.
Is a 30W adapter safe for AirPods?
Yes. The AirPods case requests about 5W and receives exactly that. Higher-capacity adapters never push current into a device.
Will a 30W charger run a MacBook Air?
Yes — 30W is the wattage Apple shipped with M-series MacBook Airs. It charges at normal speed but will not trigger fast charging, which needs 70W on the models that support it.