CPM
Cost per thousand impressions: what you pay to be seen, before anyone does anything.
Meta prices attention through an auction, and this is the price. It moves with competition, with audience, with placement and with the season.
Why it matters for HVAC
It is the number that shows you the seasonal auction most clearly. Every contractor in a metro raises budget in the same week, because the same weather told all of them to, and the price of attention rises for everyone at once.
It is also the fastest way to separate a market problem from an account problem. Rising across every campaign at once with click-through flat is the auction. Rising in one campaign with click-through falling is fatigue.
How it is measured
Reported directly, and most useful plotted weekly against frequency and link click-through rate. Compare year on year rather than month on month, because the seasonal shape dominates.
A worked example
An account sits around $14 through spring. The first sustained heat arrives and it reaches $26 within ten days, with click-through unchanged. Nothing is wrong with the ads; the metro has started bidding. A contractor who built warm audiences in the shoulder season is now reaching them at a fraction of what cold reach costs.
These figures are invented to show the arithmetic. They describe no real business.
Where this is demonstrated
The Creative production pillar scores every listed agency on what they document here, and gives you the questions that tell you which one you are being sold.