Many performance marketers managing Search campaigns on Microsoft Advertising face a common dilemma: while Enhanced CPC (eCPC) yields steady conversions, switching to Target CPA (tCPA) often increases impressions without improving cost efficiency or lead quality. Understanding how mature Microsoft’s automated bidding algorithms are—and whether lower-budget accounts should remain on eCPC—requires examining where control sits in each model.

eCPC vs. tCPA: Control vs. Automation

The main difference between the two strategies lies in how much control remains with the advertiser versus the platform system:

  • Enhanced CPC (eCPC): Retains manual bid control at the keyword or ad group level. Microsoft dynamically adjusts your base bids in real-time based on conversion likelihood—bidding higher for high-intent auctions and lower for low-probability traffic—while keeping long-term average CPC near your target bid.
  • Target CPA (tCPA): Handles bidding entirely through real-time algorithm signals. You set a target cost-per-acquisition, and the platform adjusts individual auction bids to achieve an overall average CPA close to your target across a given period.

Data Requirements and Conversion Volume

Microsoft officially recommends setting up reliable Universal Event Tracking (UET) and accumulating at least 30 conversions within the past 30 days before evaluating smart bidding performance. Low-volume accounts often face issues when attempting automated strategies without sufficient data signal.

For example, in a CPL lead generation account that yields only a dozen leads per month—many of which require sales follow-up to verify quality—setting an aggressive tCPA limits the signals available to the algorithm, causing performance fluctuations. Conversely, accounts with steady conversion volume, verified UET tracking, and short conversion paths allow tCPA to effectively leverage contextual auction signals without manual keyword adjustments.

Important Policy Update: August 2025

Marketers should take note of an upcoming policy shift: starting August 4, 2025, Microsoft Advertising will no longer allow advertisers to select a standalone Target CPA strategy when creating new standard campaigns. Instead, setting a Target CPA will require choosing Maximize Conversions with a Target CPA parameter. Existing standalone tCPA campaigns created prior to this date will remain unaffected.

Best Practices for Campaign Selection

When deciding between bidding options, evaluate your account using the following criteria:

  • Low Volume or Exploration Phase: Stick with eCPC to maintain manual control, while actively monitoring search query reports and keyword quality scores.
  • Consistent Conversions & Accurate Tracking: Test Maximize Conversions + Target CPA to evaluate if the system can sustainably scale within your target cost bounds.
  • Long Conversion Cycles (>7 Days): Exercise caution. If a significant portion of conversions occurs more than 7 days after the initial click, automated bidding models may struggle to optimize effectively.

Optimization Tip: Avoid evaluating smart bidding performance after only two or three days. Allow a 1 to 2-week learning period for automated strategies to calibrate before measuring baseline performance.

Ultimately, neither strategy is inherently superior. The decision comes down to whether your account possesses enough reliable conversion data for Microsoft's algorithm to bid effectively on behalf of your business goals.