Phone makers increasingly advertise their fast-charging wattage — 45W, 80W, even 120W — but what do these numbers actually mean, and why aren’t all chargers created equal?
How it works
Fast charging increases the power (measured in watts) delivered from the charger to the phone, cutting down the time needed to reach a full or near-full charge. Power is the product of voltage (volts) and current (amps): fast-charging protocols dynamically negotiate these values between charger and phone to find the fastest combination the device can handle safely.
The main standards
USB Power Delivery (USB PD) is the most widespread, universal standard, supported by most recent Android smartphones and iPhones. With the PD 3.1 revision it can reach up to 240W, though no current smartphone gets anywhere close to that figure — it’s built more for laptops and monitors.
Many Android makers — Xiaomi, OPPO, Realme, among others — also use proprietary protocols reaching up to 80-120W, faster than standard PD but requiring the manufacturer’s original (or a certified) charger to hit top speed: with a generic charger, the phone will usually still charge, just at a lower power.
What about wireless charging?
The Qi standard (and its evolution, Qi2) allows cable-free charging by placing the phone on a pad. Qi2 raised the ceiling from 15W to 25W, and the Wireless Power Consortium has already paved the way for 50W down the line — but it remains slower than wired charging on the same phone.
What actually matters
The wattage printed on a charger is a ceiling, not a guarantee: if the phone supports a maximum of 45W, charging it with a 100W power adapter won’t make it go any faster than that. To hit the speed advertised by the manufacturer you typically need both a compatible charger and a cable certified for that power level — a cheap cable can become the bottleneck even with the right charger.