Follow the ‘plus 5’ rule to restore iPhone wireless charging speed

At a glance:

• Use a wall adapter that provides at least 5 W more than the charger’s maximum output (e.g., 20 W brick for a 15 W Qi2 pad).
• A 20 W USB‑C power brick is the baseline for fast iPhone wireless charging; higher‑wattage (45 W‑67 W) GaN adapters work well for multiple devices.
• Avoid low‑wattage or uncertified adapters (e.g., cheap Temu bricks) to prevent throttling from 15 W to much slower speeds.

Why wireless chargers can be slow

Wireless charging is inherently less efficient than wired charging because some energy is lost to heat and magnetic field leakage. That loss becomes noticeable when the power source feeding the pad cannot supply the charger’s rated wattage. Plugging a 15 W Qi2 pad into a low‑output wall brick—especially one that is not certified—will often throttle the pad’s output, turning a “fast wireless charging” experience into a sluggish trickle. As ZDNET colleague Kerry Wan observed, mismatched adapters are a common cause of the problem in home offices where cords are swapped without a second thought.

The “plus five” rule explained

The rule is simple: choose a power adapter that delivers 5 W more than the wireless charger’s maximum advertised output. For most iPhone‑compatible MagSafe pads that list 15 W fast charging, a 20 W USB‑C wall brick satisfies the rule and restores the advertised speed. Apple’s own guidance echoes this, recommending a 20 W adapter for iPhone fast charging, while standard charging can be done with a 5 W USB‑A or a 15 W USB‑C port. By staying 5 W above the pad’s limit, you give the charger enough headroom to overcome inefficiencies and avoid throttling.

Recommended wall adapters

The ZDNET testing team found several adapters that meet or exceed the “plus five” guideline:

• Anker 45 W GaN charger – features a built‑in digital display and works well for multiple devices.
• Ugreen 65 W wall brick – reliable for higher‑power laptops and can still charge phones efficiently.
• Apple 20 W USB‑C power adapter – the baseline for iPhone MagSafe fast charging.
• Apple 67 W USB‑C charger – recommended for MacBook Pro but also plenty powerful for wireless pads.
• Any certified 20 W+ GaN charger – ensures compact size and high efficiency.

When you share a single adapter among several devices, the total wattage is split, which can drop each device’s charging rate back into the “slow” zone. Keeping a dedicated adapter for your wireless pad eliminates this risk.

How to avoid common pitfalls

First, always use the cable and brick that come with the wireless charger, or replace them with a certified, higher‑wattage alternative. Second, steer clear of cheap, unverified adapters sold on marketplaces like Temu; they may lack proper safety certifications and can introduce voltage irregularities. Third, if you travel internationally, opt for a universal‑input GaN charger (45 W‑65 W) that accepts 100‑240 V, so you never have to compromise on wattage abroad. Finally, monitor charging performance via your phone’s lock‑screen indicator—if it no longer shows “fast wireless charging,” it’s a sign the power source is insufficient.

Conclusion

Wireless charging can feel magical, but only when the power path is correctly sized. By applying the “plus five” rule—matching a 20 W (or higher) wall adapter to a 15 W pad—you restore the advertised fast‑charge speeds and protect your devices from inefficient charging cycles. With the right GaN charger in hand, you’ll enjoy a tidy desk, fewer cords, and consistently speedy wireless power.