In a recently updated support document, Apple has indicated that its new MagSafe Charger will be limited to 12W peak power delivery when used with the upcoming iPhone 12 mini, compared to up to 15W for all other iPhone 12 models.
Apple says the iPhone 12 mini can achieve this 12W with a USB-C Power Delivery power adapter that is at or above 9V/2.03A. However, the support document notes that power delivered to any iPhone 12 model at any moment will vary depending on various factors, including temperature and system activity.
For other iPhone 12 models, peak 15W power can be achieved with a USB-C Power Delivery power adapter at or above 9V/2.22A or 9V/2.56A, according to Apple.
The support document also notes that when Lightning accessories such as EarPods are connected to any iPhone 12 model, the MagSafe Charger is limited to 7.5W charging to comply with regulatory standards.
Apple says the MagSafe Charger should be connected to a power source before placing an iPhone on it, as this allows the charger to verify that it is safe to deliver maximum power. If you place your iPhone on the MagSafe Charger before plugging it in, simply remove your iPhone, wait three seconds, and then put it back on to resume maximum power delivery.