While a blended CAC is the North Star metric, don't discard individual channel analysis. Use siloed metrics to diagnose problems. When your overall blended CAC increases, dive into the channel-specific data to identify the underperforming source, such as ad fatigue on a specific platform.
Instead of optimizing each channel in isolation, establish a single blended CAC target across all marketing efforts. This provides a holistic view of performance, preventing premature cuts to channels that assist conversions attributed elsewhere. It acts as a single health metric for your entire acquisition strategy.
Channels with high direct CAC often contribute to brand awareness that results in conversions on other platforms. A siloed view would cut these channels. A blended CAC approach values their overall contribution, allowing longer-term, brand-focused plays to run without being penalized for poor last-touch attribution.
Lumping all search keywords together inflates performance, as branded search has a much lower effective CAC. People searching your brand name already know you from other channels. To accurately assess Google's performance and understand true customer acquisition, analyze the CAC for branded and non-branded keywords as distinct categories.
When testing a new channel, don't isolate its budget or performance. Immediately include it in your overall blended CAC calculation. Because the initial test spend is typically small relative to your total budget, it won't significantly skew the metric but provides an accurate, holistic view of acquisition costs.