Which charger for your phone? Watts, USB-C and what really counts

These days the box usually only holds a cable. You buy the power adapter separately, and there is surprisingly much you can get wrong: too weak, and the phone charges at a snail's pace. Too expensive, and you pay for watts your device never draws. Here is the short version of what matters.

How many watts does your phone need?

A charger never delivers more than the device requests. A 65 watt adapter therefore does not damage a phone, it simply charges as fast as the phone allows. As a rough guide:

• 20 to 30 watts: enough for practically every current smartphone to reach its fastest charging level.
• 30 to 45 watts: sensible if a tablet charges alongside.
• From 60 watts: interesting if a notebook runs off the same adapter.

If you only charge a phone, 100 watts mainly buys you weight. If you supply phone, tablet and notebook on a trip, a strong multi port adapter saves you real space in your backpack.

USB-C Power Delivery is the common denominator

Look for the Power Delivery label, PD for short. That is the standard Apple, Samsung, Google and most others have agreed on. A PD adapter negotiates with the device which voltage flows. Manufacturer specific fast charging methods still exist, but PD works across all brands and is therefore the safe choice if not everyone in the household has the same phone.

Why GaN adapters are smaller

GaN stands for gallium nitride, a semiconductor material that produces less waste heat than classic silicon. In practice that means the same output in a much smaller housing. A 45 watt GaN adapter is often barely larger than an old 20 watt model. If you plug the charger in and carry it with you every day, that is the most noticeable gain in comfort, and the one worth paying for.

The cable has a say too

A strong adapter on a weak cable achieves nothing. For high output the cable needs the right rating, and cables without clear labelling often deliver less than they claim. If your phone suddenly charges more slowly than before, surprisingly often the cable is to blame and not the battery. You can find suitable adapters and cables with us under power and cables. Why cheap no-name cables are a bad deal is something we wrote up here.

When a new charger no longer helps

If your phone only charges at certain angles or not at all despite a new adapter and a new cable, the charging port is usually the cause. It clogs up with lint or gets mechanically tired from plugging in and out. That is a standard repair, not a reason for a new device, more on that at the charging port repair.

Conclusion

For a phone on its own a solid USB-C adapter with around 30 watts and Power Delivery is enough. If you supply several devices, go for GaN with several ports. And in both cases: saving on the cable is saving at the wrong end.