Attribution setting
The rule deciding how long after seeing or clicking an ad a conversion still counts as caused by it.
Meta’s default is seven days after a click and one day after a view. Widen it and the same campaign reports more conversions at a lower cost, without anything changing in the world. Narrow it and the same campaign looks worse.
Why it matters for HVAC
Reported performance is partly a function of a setting, and most contractors have never been told which one their account uses. Two agencies quoting cost per acquisition on the same account can differ by a wide margin and both be telling the truth about the number in front of them.
The view window matters more here than people expect. A one-day view credit means someone who scrolled past your ad without clicking, then called you the next day, is counted as a conversion. Sometimes that is genuinely what happened. Sometimes they were always going to call.
How it is measured
It is set at the ad set level and can be requested explicitly when pulling reports. The honest practice is to state it beside every conversion figure. A cost per acquisition without its window is not a number, it is a rumour.
A worked example
An account reports 40 leads at $75 on seven-day click plus one-day view. Requested on one-day click only, the same period shows 26 leads at $115. Nothing changed except which rule was applied, and both numbers are real.
These figures are invented to show the arithmetic. They describe no real business.
What to ask
Ask what window your reports use, then ask them to show you the same month on a narrower one. The gap between the two is the size of the claim you are being asked to trust.
Where this is demonstrated
The Tracking and the Conversions API pillar scores every listed agency on what they document here, and gives you the questions that tell you which one you are being sold.