You bought a charger with a big “15W” on the box, dropped your phone on it, and hours later it is barely topped up while a cheap cable would have done the job in a fraction of the time. You are not imagining it, and the pad is not necessarily faulty. The number on the box is almost never the speed your phone actually accepts.
Wireless charging is convenient, but the wattage printed on a pad is a best-case ceiling that depends on your exact phone, whether there are magnets involved, how well the coils line up, and how much heat builds up. Here is why a “15W” charger so often delivers far less, and how to get the most out of it.
The watt rating is the pad’s maximum output, not what your phone takes. Plain (non-magnetic) Qi charging caps most iPhones at 7.5W no matter what the pad claims, and open Qi on Android often underdelivers because the coils do not line up. Magnetic Qi2 and MagSafe fix the alignment and unlock the full 15W (and more on the newest iPhones), while the fastest Android wireless speeds only work with the phone maker’s own matching stand. Wireless is also less efficient than a cable, so a chunk of that power is lost as heat.
What you put it on vs. what the phone actually takes
| Setup | Realistic charging speed |
|---|---|
| iPhone on a plain Qi pad (no magnets) | About 7.5W |
| iPhone on MagSafe / Qi2 (magnetic) | Up to 15W; newest iPhones up to 25W with a strong enough adapter |
| Android on open Qi | Often 5–10W, depending on alignment |
| Android on the maker’s own fast stand | 15W to 50W+ (proprietary, brand-matched only) |
| Any phone on a cable (USB-C PD/PPS) | Much faster, with far less heat |
The watt number is the pad’s ceiling, not your phone’s
Charging is a negotiation. When your phone sits on a pad, the two talk to each other and agree on a power level the phone is willing to accept at that moment, based on its hardware, its temperature and its current battery level. The “15W” on the box is simply the most the pad can ever push out. If your phone only supports 7.5W wireless, the pad delivers 7.5W and the other half of that headline number is irrelevant. Buying a higher-rated pad does not raise the speed your phone is built to take.
Why plain Qi is slower than it sounds
Standard, magnet-free Qi charging has two problems. First, Apple deliberately caps iPhones at 7.5W on ordinary Qi pads, reserving faster speeds for its magnetic system. So a non-magnetic “15W” pad charges an iPhone at 7.5W, full stop. Second, wireless charging relies on two coils lining up precisely; on a flat pad it is easy to set the phone down slightly off-center, and even a small misalignment drops the power or stops charging overnight when you thought it was topping up. That is why people wake up to a phone that barely charged.
Qi2 and MagSafe: magnets fix the alignment
This is the real upgrade. MagSafe (Apple) and the newer industry-wide Qi2 standard add a ring of magnets that snap the phone into perfect coil alignment every time. Qi2 standardizes magnetic charging at 15W for phones that support it, and Apple’s latest iPhones can go higher still — up to 25W on MagSafe with a sufficiently powerful adapter. The magnets are not a gimmick; consistent alignment is most of what separates a fast, reliable wireless charge from a slow, hit-or-miss one. If your phone supports Qi2 or MagSafe, a magnetic charger is worth far more than a higher wattage number on a flat pad.
Android “fast wireless” is usually proprietary
Some Android phones advertise eye-catching wireless speeds — 15W, 30W, even 50W and beyond. The catch is that those top speeds almost always rely on the manufacturer’s own charging profile and only kick in with that brand’s matching wireless stand. Put the same phone on a generic Qi pad and it falls back to the slow open-standard rate. If fast wireless charging matters to you on Android, you generally have to buy the phone maker’s own charger, not a third-party “fast” pad.
The hidden cost: heat and efficiency
Wireless charging is inherently less efficient than a cable. Some of the energy that leaves the pad never makes it into the battery; it is lost in the air gap and the coils, and it comes out as heat. That heat is not just wasted electricity — it is also why wireless charging can feel slow. Phones protect their batteries by throttling charge speed when they get warm, so a hot phone on a pad (especially under a thick case or in a warm room) will deliberately slow down. The convenience of wireless is real, but so is the trade-off in speed and efficiency.
How to actually charge faster wirelessly
Do this
Use a magnetic Qi2 or MagSafe charger if your phone supports it, paired with a wall adapter rated for its full speed. Line the phone up centrally, take off thick or metal-backed cases, and keep it somewhere cool. On Android, use your phone maker’s own fast stand to unlock its top speed.
Not that
Do not assume a bigger wattage number on a flat, magnet-free pad means faster charging — it usually does not. And when you actually need speed (you are heading out the door), skip the pad and use a cable.
When speed genuinely matters, wired is still king: a good USB-C cable and the right adapter will outpace any wireless pad and run cooler doing it. If you want the full picture on getting maximum wired speed, see our guide to PPS fast charging and what your USB-C cable can actually do. Treat wireless charging as the convenient, top-up-while-you-work option it is — not the fastest way to fill an empty battery.
Frequently asked questions
Why does my iPhone charge at only 7.5W on a 15W wireless charger?
Because it is a plain, non-magnetic Qi pad. Apple caps iPhones at 7.5W on standard Qi charging and only allows the full 15W (or more) through its magnetic MagSafe and the Qi2 standard. A flat pad without magnets cannot trigger the faster rate, no matter what wattage is printed on it.
Is Qi2 the same as MagSafe?
They are closely related. Qi2 is the industry-wide standard that adopted the magnetic alignment ring Apple pioneered with MagSafe, charging supported phones at 15W. MagSafe is Apple’s own implementation, and on the latest iPhones it can go up to 25W with a powerful enough adapter. Both use magnets to lock the coils into alignment.
Why does wireless charging make my phone hot?
Wireless charging is less efficient than a cable, and the energy lost in the gap between the coils turns into heat. Because phones slow charging to protect a warm battery, that heat is also part of why wireless feels slow. A thick case or a warm room makes it worse.
Why is my Android phone’s wireless charging slower than advertised?
The fastest wireless speeds Android makers advertise usually require that brand’s own matching charging stand and proprietary profile. On a generic Qi pad, the phone falls back to the slower open-standard rate. To hit the headline speed, you generally need the manufacturer’s own charger.
Is it faster to charge with a cable or wirelessly?
A cable is almost always faster and cooler. A good USB-C cable with the right adapter outpaces any wireless pad, while wireless loses energy as heat and throttles when warm. Use wireless for convenient top-ups and a cable when you need to fill an empty battery quickly.