Have you ever wondered if you could use the power adapter that came with another model of Mac laptop with your Mac laptop? In most cases, the answer is yes, but there are a few details to be aware of. Apple’s Support article on the subject states the following. “You can use a compatible higher wattage adapter without issue, but it won’t make your computer charge faster or operate differently. Lower wattage adapters will not provide enough power.” Let me elaborate on what Apple states in their support article.
I think it is helpful to start by talking about the two connectors you’ll find on Apple’s power adapters made between 2006 and the present (early 2016). In about 2006, Apple introduced the original MagSafe adapter. In about 2012, Apple switched to a thinner version of this adapter called the MagSafe 2 adapter. One can buy a MagSafe to MagSafe 2 adapter to let the older adapter fit into a laptop which requires the thinner MagSafe2 connector. Unfortunately, the opposite is not possible. There is no way to make a thinner MagSafe 2 power adapter fit into an older Mac laptop which requires the thicker, original, MagSafe connector.
It is always fine to use a higher wattage (i.e. 85 or 60 watt) power adapter on a Mac that shipped with a lower wattage (i.e. 45 or 60 watt) power adapter as long as the adapter’s connector fits (see MagSafe discussion above) on your Mac laptop. For example, you could use a 13-inch MacBook Pro’s 60 watt power adapter on a 13-inch MacBook Air, which shipped with a 45 watt power adapter. The power rating (aka wattage) of the adapter indicates the maximum power that it can supply. A laptop that consumes less power will simply pull less power, fewer watts, from the power adapter.
It’s not always fine to use a lower wattage power adapter on a laptop that consumes more power than the power adapter can provide. Apple’s support article indicates that lower wattage adapters will not provide enough power. I agree with this, but a bit more explanation can be helpful. A lower wattage power adapter can’t provide enough power to both operate the laptop and charge it, but a lower wattage power adapter could be used, in a pinch, to either temporarily power or charge the laptop’s battery. Notice that I said that this could be done short-term. It is dangerous to regularly use a lower wattage power adapter with a laptop that draws more power. It is not good for the laptop and it will strain the power adapter and could cause the adapter to burn out or fail in some way. If you were to use a lower wattage adapter to charge a higher wattage laptop’s battery, the battery will charge more slowly than it would if you were to use the proper, higher wattage, power adapter.
Perhaps, I will write a future Tech Tip about mixing iPhone and iPad power chargers. In the meantime, here’s a brief overview. You can safely use an iPad’s higher wattage power adapter to charge your iPhone. It’s not prudent to use an iPhone’s lower wattage power adapter to charge your iPad regularly, but you could use it briefly.