Neosignal Electronics and parts from AliExpress, measured before listing

USB-C power delivery — reading the numbers on a cheap charger

A listing saying "100W" is making a claim about one specific voltage. Whether your device gets 100 W depends on figures further down the page.

USB-C Power Delivery listings lead with a single wattage. That number is close to meaningless on its own, because Power Delivery does not deliver a wattage — it negotiates a voltage and a current, and the wattage is whatever those multiply to.

What decides whether your laptop charges at full speed is which voltage and current pairs the charger actually offers, and that list is usually printed in small text below the marketing number.

The PDO list is the specification

A PD source advertises Power Data Objects — the fixed combinations it supports. A typical list looks like:

5V/3A  9V/3A  12V/3A  15V/3A  20V/5A

The device picks the highest one it can use. A laptop that wants 20 V will negotiate 20 V/5 A and draw 100 W. A phone that wants 9 V takes 9 V/3 A and draws 27 W, from the same charger.

Now consider a listing headlined 100W whose PDO list ends at 20V/3A. That is 60 W, not 100. The “100W” is either the sum across multiple ports or simply wrong, and a laptop needing 20 V/5 A will charge slowly or not at all.

Always read the PDO list. If a listing does not print one, that is the answer.

Multi-port maths

Multi-port chargers advertise the total across all ports, which is never available on any single one.

A “140W” three-port charger commonly means: 100 W if you use one port, but plugging in a second drops the first to 65 W and gives the second 45 W. The split is fixed in the design, printed in a table on the listing, and frequently absent from the title.

If you intend to charge a laptop and a phone at once, the number you need is the laptop port’s wattage when a second port is occupied, not the headline.

What 5 A requires from the cable

Anything above 60 W means 20 V at more than 3 A, and that requires a cable with an e-marker chip identifying it as 5 A rated. Without it, the charger will not negotiate above 3 A regardless of what both ends support.

This is the most common reason a correct charger charges slowly. A cable that looks identical, works for data, and carries 60 W happily will silently cap a 100 W charger at 60 W.

Cables rated for 5 A cost more and say so. Cables that do not mention it are not.

PPS, and why it matters for phones

Programmable Power Supply is an extension that lets a device request a voltage in small steps rather than picking from the fixed list. Modern phones use it to charge faster and cooler, because the charger can track the battery’s actual needs instead of stepping down internally.

A listing that supports PPS says so and specifies a range, such as 3.3-21V/5A. Fast charging on recent Samsung and Google phones depends on it. A charger without PPS still works; it charges more slowly and runs the phone warmer.

GaN, and what it does and does not buy

Gallium nitride switching lets a charger be physically smaller and run cooler at the same output. It is a real advantage, and it is also the most heavily advertised term in this category — applied to plenty of chargers whose PDO list is mediocre.

GaN tells you about size and heat. It tells you nothing about whether the thing delivers the power it claims.

Reading a listing in order

  1. The PDO list. No list, no purchase.
  2. The 20 V current. 5 A for 100 W, 3 A means 60 W whatever the title says.
  3. Per-port split, if it is multi-port and you will use more than one.
  4. PPS range, if you are charging a recent Android phone.
  5. Whether a 5 A cable is included — often it is not.
  6. Then GaN, size, colour, and everything else.

What you cannot verify from a listing

Whether the protection circuitry is real. A charger negotiating 20 V into a device that asked for 5 V destroys it, and the components preventing that are invisible in photographs and absent from specifications.

This is the one place in this category where an unbranded purchase carries a risk the numbers cannot address. For charging an expensive laptop, it is worth weighing against what the saving actually is.

The short version

The headline wattage is marketing. The PDO list is the specification. Check that 20 V line, check the per-port split, and check whether the cable in the box is rated for what the charger can deliver — those three lines decide whether the thing does what the title says.