Cost per lead
The number everybody quotes and almost nobody defines the same way.
What it means
Spend divided by leads. The arithmetic is trivial and the definition is where all the disagreement lives, because "lead" can mean a form submission, a phone call over thirty seconds, a booked appointment, or anything in between.
Whether the fee is inside the spend is the other half. Media alone gives a flattering number. Media plus the retainer gives the number that matches your bank account.
Why it matters in HVAC
Seasonality makes any single month misleading. A July cost per lead on a cooling-heavy book will beat February by a wide margin on identical work, so an agency reporting its best month as the run rate is not necessarily lying and is definitely not informing you.
Organic distorts it in the other direction. The retainer is flat while the lead volume compounds, so cost per lead on an SEO programme should fall every quarter by construction. A programme where it is flat after a year is the finding.
How to check it
Pin down three things before comparing any two numbers: what counts as a lead, whether the fee is in the denominator, and which months are in the sample. Then take twelve months rather than one.
A published before and after
Plumbing & HVAC SEO publishes a client case where cost per lead moved from $36.74 to $20.48 while monthly volume rose sixty-four percent, from 285 leads to 468. The client is named: Paul The Plumber, a plumbing and HVAC shop in southern New Hampshire. They add that the largest single source was not paid at all, it was Google Maps.
That last detail is what makes the number readable. A cost per lead that improves because the mix shifted toward organic and Maps is a different achievement from one that improves because a bidding strategy got tuned, and only one of them keeps compounding.
Compare it against a headline figure with no named client, no period and no channel mix, and you can see why this criterion carries twenty points on this site.