The iPhone 12 mini will charge about 20 percent slower than its larger siblings with the MagSafe Charger. According to a support document (via MacRumors), the charger is limited to peak power delivery of 12W for that handset, compared with 15W for the rest of the iPhone 12 lineup.
You'll need a USB-C Power Delivery adapter that's at least 9V/2.03A to hit 12W MagSafe output on iPhone 12 mini, though Apple notes charging efficiency can be affected by factors like system activity and temperature. Reaching peak power delivery of 15W on other iPhone 12 models requires a USB-C adapter that’s at least 9V/2.22A or 9V/2.56A.
If you have an accessory connected via the Lightning port, the MagSafe Charger's power delivery is limited to 7.5W on all iPhone 12 models to comply with regulatory standards.
While slower charging via one method of powering up your phone might not sway your decision over which phanset to get next, it's useful to know if you were considering picking up MagSafe accessories. Pre-orders for the iPhone 12 mini and iPhone 12 Pro Max open on Friday, and the phones should start shipping on November 13th. The iPhone 12 and iPhone 12 Pro are already available.