Wattage · Legacy USB-A
5W adapters: 5 volts, 1 amp, and nothing to negotiate.
A 5W brick is a single fixed rail — 5V at 1A over USB-A, with no Power Delivery handshake of any kind. It is the slowest thing you can plug a modern phone into, and it is still exactly right for three classes of device.
The electrical picture
5V × 1A = 5W. That is the entire specification. There is no voltage step to 9V, no current negotiation, no PPS — the classic Apple cube (A1385) measured 5.1V at 1A and generic cubes copy it. Because conversion losses eat 10–15%, roughly 4–4.5W actually reaches the battery cell. Compare that with a 20W USB-C adapter, which raises the bus to 9V and delivers four times the power over the same wire gauge.
USB-A can only signal available current through Battery Charging 1.2 resistor codes or Apple's D+/D− divider trick; neither is a real protocol. That ceiling is why the industry abandoned 5W entirely once USB-C Power Delivery made 9V and 15V rails routine.
What 5W still charges at full speed
| Device | Its actual draw | On a 5W brick |
|---|---|---|
| AirPods / earbud charging case | ~2.5–3W | Full native speed |
| Fitness band, Bluetooth tracker | 1–2.5W | Full native speed |
| Kindle / e-reader | ~4.5W | Full native speed |
| Older Apple Watch puck | 2.5–5W | Normal; fast charge needs USB-C |
| iPhone 8 / SE-class | Accepts 5W | Shipped speed, ~2½ hours |
| iPhone 15/16/17 | Wants 20–27W | Charges, roughly 3× slower |
| iPad 10.2″ or newer | Wants 12–20W | Barely gains ground while in use |
The pattern is simple: anything with a battery under about 1,000 mAh is already at its own ceiling on 5W, so a bigger adapter buys nothing. Everything above that is being throttled by the brick.
Picks at this wattage
- 5W
Apple 5W USB Power Adapter (A1385)
The reference 5W cube. Still the correct replacement for an Apple Watch puck or an older iPhone that lives on a nightstand.
- Output
- 5V/1A
- Port
- 1× USB-A
- Input
- 100–240V
- 5W
Certified 5W USB-A cube, multipack
Class pick: buy UL- or ETL-listed multipacks so every room has one. Check the listing photo for a printed 5V/1A rating and a real certification mark.
- Output
- 5V/1A
- Port
- 1× USB-A
- Look for
- UL/ETL mark
- 5W
5W USB-A cube with folding prongs
Class pick for luggage. Same single rail, but the pins fold flat so it does not gouge a bag — and 100–240V input means it works worldwide with a plug adapter.
- Output
- 5V/1A
- Port
- 1× USB-A
- Prongs
- Folding
When to size up
Size up the moment a phone or tablet is involved. The honest steps from here are 10W (5V/2A) and 12W (5.2V/2.4A) if you are staying on USB-A, or a jump straight to 20W USB-C PD, which is where fast charging actually begins. If you are replacing a cube that went missing, our lost charger guide maps the original brick to its modern equivalent, and the USB-A adapter guide explains what that port can and cannot do. 5W is overkill for nothing — it is the floor of the range.
FAQ
Will a 5W charger damage a new iPhone?
No. The phone requests what it can take and a 5W supply simply never offers more. It is slow, not harmful, and it produces less heat than a fast charge does.
How long does a 5W adapter take to charge a phone?
For a small older phone, roughly two to three hours from empty. For a modern 4,000 mAh phone, expect four hours or more, because 5W is close to the device's idle draw.
Is a 5W USB-A charger the same as a 5W USB-C charger?
Electrically, almost: both hold 5V. USB-C ports advertise current through a CC resistor rather than Apple's divider, but neither reaches 9V, so charging speed is unchanged.