USB-C Power Delivery Explained: Watts, Volts, PPS and Why 65W Marketing Lies
USB-PD is a negotiation, not a number. Understand watts, volts, PPS, and how to tell whether a charger will actually hit its claimed speed on your device.
“65W charger” tells you the maximum the charger can supply — not what your phone will actually receive. USB Power Delivery is a negotiation between charger and device, and most of the spec sheet is irrelevant to what happens in your hand.
The core formula
Watts = Volts × AmpsA charger can deliver high wattage in different ways, and the voltage side is what makes fast charging on phones possible.
- A 65W laptop charger typically does 20V × 3.25A. Plug a phone into it and the phone will often pull only 9V or 5V — because that’s all it negotiated.
- A 30W phone charger might do 9V × 3A, which can charge a phone faster than the 65W brick if the phone doesn’t support 20V input at all.
Wattage is a ceiling, not a delivery promise. Two 65W chargers can produce wildly different charging curves on the same phone.
Fixed PDOs vs. PPS
Chargers advertise “profiles” — fixed voltage/current combinations:
| Profile | Typical use |
|---|---|
| 5V / 3A (15W) | Universal fallback. Works on everything. |
| 9V / 2–3A (18–27W) | QC and PD phone fast charging. |
| 12V / 3A (36W) | Mid-power, some laptops. |
| 15V / 3A (45W) | Laptops, some tablets. |
| 20V / 3.25A (65W+) | Laptop charging. |
PPS (Programmable Power Supply) is the important one for phones. Instead of a fixed set of steps, PPS lets the phone request any voltage in small increments — typically 3–21V in 20mV steps — so the charger can track the battery’s ideal charging curve in real time.
Why you care: Samsung Galaxy devices and Google Pixel phones depend on PPS for their advertised “Super Fast Charging” / “fast charging” speeds. Without PPS, the same phone on a non-PPS PD charger charges at plain PD 9V speeds — noticeably slower, and often less than half the advertised peak.
[!warning] A charger can carry a genuine 65W PD badge and still charge a PPS-dependent phone slowly. “PD 3.0” is not the same as “PPS”. Look for PPS explicitly listed.
How to check what a charger really does
- Read the profile list, not the wattage. A good spec sheet lists each PDO (e.g. 5V/3A, 9V/3A, 15V/3A, 20V/3.25A) and states PPS support.
- Check port sharing. Multi-port chargers split budget. A 100W three-port brick may cap at 45W + 30W + 22W depending on which ports are used — and many renegotiate when you unplug something else.
- Check cable capability. The cable is the most common bottleneck. A USB-C cable rated only for 60W will silently limit a 100W charger. Look for a 5A e-marker chip for anything above 60W.
- Thermal throttling is real. Small GaN chargers sustain peak wattage for a limited time before reducing output. Sustained ratings matter more than peak for laptops.
GaN: what it actually buys you
GaN (gallium nitride) allows the same power in a smaller, cooler package. The benefit is size and heat, not speed. A 30W GaN charger is not faster than a 30W silicon one — it’s just smaller. What you should expect from a good GaN design:
- Comparable sustained output in a fraction of the volume
- Lower surface temperature at the same load
- Often better multi-port behaviour
Common marketing claims, decoded
| Claim | Reality |
|---|---|
| “65W for your phone” | Your phone probably negotiates 18–27W. The rest is unused capacity. |
| “Charges 50% in 20 minutes” | Usually measured from 0% in airplane mode with the screen off, on the manufacturer’s own charger. |
| “GaN 3 / GaN II” | Marketing generations. Performance is set by the profile list, not the GaN version. |
| “100W in your pocket” | Check sustained, not peak. Small bricks throttle hard. |
| “Universal compatibility” | True for the 5V fallback — but not for the fast-charge modes you’re buying it for. |
Practical buying rules
For a phone only: A 30–45W charger with explicit PPS support charges a modern flagship faster than a 65W brick without it. Prioritise PPS, ports, and cable quality over wattage.
For a laptop plus phone: 65W minimum, ideally with at least one PPS-capable port for the phone. Confirm the laptop’s own requirement — 65W doesn’t charge every 14” laptop at full speed under load.
For travel: One 65W three-port GaN charger with a rated 100W cable beats three separate bricks. Verify the per-port breakdown rather than the summed number.
Wattage and profile figures above describe how USB-PD works rather than any specific product’s performance. Check the profile list on your own charger and cable before assuming you’re getting the speed you paid for.