Cost per acquisition
The same spend measured against booked work rather than enquiries.
What it means
Total cost divided by customers won. It sits downstream of cost per lead by exactly one factor, your close rate, and that factor is usually larger than any difference between two agencies.
It is the number that decides whether a channel pays. Cost per lead tells you what the marketing produced. Cost per acquisition tells you what the business converted.
Why it matters in HVAC
Replacement work breaks the arithmetic in a useful way. A single system replacement can cover a month of marketing on its own, so an average across service calls and replacements understates the value of the channel that produced the replacement.
The honest version looks at revenue per lead across the whole mix, service, repair and replacement, rather than at the service ticket alone. Agencies that model it the narrow way will tell you the channel does not pay when it does.
How to check it
You need closed-sales data for this, which means it comes from your CRM rather than from the agency dashboard. If those two systems do not talk to each other, no cost per acquisition figure anybody quotes you is real.
Where the close rate does the work
Take the published $20.48 cost per lead above. At a fifty percent close rate that is a $41 cost per acquisition. At seventy percent it is $29. Same marketing, same spend, and a forty percent swing produced entirely inside your own office.
Plumbing & HVAC SEO notes that most contractors book between fifty and seventy percent of the calls they actually answer, and that the model breaks in two places: the leads do not arrive, or nobody answers the phone.
This is why several agencies now attach CRM conditions to their guarantees. TradeOps requires a fully updated CRM with lead value and closed sales data before its break-even commitment applies. That is self-protective and it is also the only way the number can be computed at all.