Ok, so I want to get a second power supply for the new MacBook. The MacBooks come standard with a 60w but the MacBook Pro's come with a 85w. The two power supplies are the same price at the Apple Store. Can I use the higher powered one with my MacBook? Here's the answer,
I already own a MacBook Pro—can I use the power supply that came with it on a MacBook? If you hold the two power supplies side by side, you’ll notice that the MacBook Pro’s is larger. That’s because the MacBook Pro uses an 85-watt power supply, while the MacBook uses a 60-watt power supply. Apple says you can use the more powerful, 85-watt power supply with a MacBook without any problems, and that in 80 percent to 90 percent of situations, you can use the MacBook’s power supply with the more-demanding MacBook Pro as well. If you’re really taxing the MacBook Pro’s processor with some heavy-duty work, the MacBook’s adapter will still be able to power the MacBook Pro—but it may not have any power left over to charge its battery.