If your running an acquisition based campaign through Google Adwords the Conversion Optimizer feature lets you set maximum CPA bids for your ad groups the way you would set maximum CPC bids.

Using historical information about your campaign, the Conversion Optimizer then automatically finds the optimal cost-per-click (CPC) bid for your ad each time it’s eligible to appear. You still pay for your clicks but the system will automatically adjust your bids to reach your CPA goals.

So the Conversion Optimizer sets higher CPC bids for more valuable clicks and lower CPC bids for less valuable clicks. The optimizer considers the site in the Google Network where your ad is eligible to appear, the user’s location, the user’s search query, and other factors.

However this is not a quick fix to getting lower CPAs.

To use Conversion Optimizer, you have to enable conversion tracking and you need to have a history of at least 100 conversion in the last 30 days. Also the conversion optimiser does not work so well for highly competitive search terms so sometimes it’s a bit of hit and miss. However like all of Google’s products it free so giving it a go won’t hurt the bank.