Apple made $1 billion off Google last year by having it as the default search engine in Safari, says Macquarie analyst Ben Schachter in a note this morning.

Schachter wrote his note in response to the fact that Apple seems to be shifting away from Google Maps.

Moving away from Google Maps isn't that big a deal for Google. But what if Apple moved away from Google for search? Would that hurt Google? The answer appears to be no, at least in the short term.

Schachter believes Google searches on Apple devices resulted in $1.3 billion in gross revenue. He believes Google has a 75% traffic acquisition cost associated with that revenue. As a result, Google only gets $335 million in net revenue from searches on iOS and Safari.

If Apple were to abandon Google, the impact to Google would be minor. The impact to Apple might actually be worse, since it would have to rely on search engines that are arguably inferior to Google.

In the long run, though, it could hurt Google since the iPad appears to be taking over the world. If the iPad overtakes the PC in the next 5 years and it becomes the number one way people are searching, then Google will be in trouble.

Here's the breakdown from Schachter on how he got to his number:

Deeper look at the financial impact - We know that Apple TAC is accounted for in the Google.com TAC line item reported each quarter by Google. For 2011, Google reported ~$1.5bn in total Google.com TAC. For modelling purposes, we assume that Apple represented ~66% of this TAC (though we acknowledge that this could be high), or $1bn. At a 75% TAC rate, this means that Google generated ~$1.3bn in gross search revenue through default search placement on Apple devices. In other words, this $1.3bn of search revenue ($335m net search revenue) in 2011 is at risk if Apple moves away from Google. $335m represented ~1% of net Google.com search revenue. Notably, mobile/Apple revenue is among its fastest growing revenue drivers.