Apple’s online retail store lists three MagSafe power adapters for its range of MacBook laptops – the MacBook (now withdrawn from sale), the MacBook Air and the MacBook Pro.
As shown below, each sells for a different price and the product pages list the MacBook models each is compatible with, or at least they seem to. The user comments suggest the lists aren’t quite as complete as they appear.
Apple’s support site states:
Although you should always use the proper wattage adapter for your Apple portable, you can use an adapter of a higher wattage without issue.
For instance If you have a MacBook (13-inch Late 2009) that normally uses a 60W adapter, you can also use an 85W adapter with that computer. You would not use a 45W adapter with that computer; it would not provide enough power for that MacBook. Using an adapter of higher wattage than the adapter that came with the computer will not cause the computer to charge more quickly or otherwise operate any differently than using the adapter that came with the computer.
This is pretty handy because if you have a MacBook Pro AND a MacBook Air (lots of people seem to) you can buy the charger for the most power hungry of your two laptops and use it to charge both.
But Apple’s text on their sales site doesn’t share this little tip, that’s left to the user comments.
Given the MacBook Air specific charger is £16 dearer than the apparently equally compatible 60W – £66 v £50 – one that’s some omission.
It seems this issue might affect UK customers more the those in other territories – the US, French, German, Italian Apple stores only have a single price for each of the chargers – $79 and €79 respectively – while in New Zealand just NZ$3 separate the cheapest and most expensive chargers.