I used to assume that a charger with a higher wattage rating would always charge my phone faster. It turns out the phone decides how much power to draw, and that depends on the charging standards supported by both the phone and the charger. For example, my 100W charger only charges my Samsung at roughly 25W because it does not support PPS, while a lower-rated charger with the right USB Power Delivery profile can charge it faster. Cable capabilities and multi-port power sharing can also affect the result. Do you check standards such as USB-PD and PPS before buying chargers, or do you generally use whatever came with your devices?
4 Answers
A high-wattage USB-C charger is generally safe for a phone because the phone requests the power it can use; the charger does not force its full rating into the device. If the charger lacks the right profile, though, the phone will fall back to a slower one. Some laptops can also be picky about charger identification even when the electrical rating appears sufficient.
Even with a compatible charger, peak charging speed usually lasts only for part of the charge. Phones reduce power as the battery fills or gets warm, so a charger that reaches the phone's maximum rated speed may not save as much time as expected. I mostly focus on using a reputable charger and cable rather than chasing the biggest number.
PPS is only one part of it. The charger, phone, and cable all need to support compatible power profiles, and multi-port chargers may reduce the available output when several devices are connected. It is worth checking the charger's listed PD/PPS voltages and currents instead of looking only at the headline wattage.
The wattage printed on a charger is its maximum output, not a promise that every device will receive that much. The phone and charger negotiate a supported voltage and current, and the device uses the highest compatible profile. A 45W charger with the right Samsung-compatible PPS profile can therefore outperform a 100W charger that only offers standard USB-PD levels.
That makes sense. I had been treating the wattage number as the whole story, but checking the supported profiles and cable rating is clearly more useful.