Vander Els Partners
It depends on which half of the business the ads are for, because HVAC is two businesses wearing one name, and they want two different budgets.
Repair and replacement are different searches
A homeowner whose system quit in July searches once, calls the first company that answers, and does not shop. That call is worth a service visit and, sometimes, a replacement conversation. The click is expensive because every company in the area wants that call, and the ad has to be there at the moment it happens, which means the budget cannot run out at 2pm.
A homeowner replacing a fifteen-year-old system searches for weeks. She reads, compares, asks about financing, and calls two or three companies. Those clicks are cheaper individually and there are more of them per job, and the page the ad lands on has to do real work, because she is deciding, not panicking.
Budgeting them together hides which one is producing your work.
Work it from the ticket
For each half, work backwards from your own numbers. What a service call is worth to you. What a replacement is worth. How many calls it takes to book one of each. That gives you what a call is worth in each campaign, and that is the ceiling for each. Nobody's industry average is a substitute for your own close rate.
Seasonality is the budget
An HVAC ad account that spends the same every month is wrong for at least half the year. Demand spikes with the first hot week and the first cold one, and the cost of a click spikes with it. The budget should move with the weather, carrying more in the peaks, and the campaign should be built before the peak, not during it, because an account that launches in the first heatwave is learning on the most expensive clicks of the year.
What to cut before you spend
The searches that waste HVAC money are predictable: filter sizes, how-to questions, parts, the brands you do not service, and the towns past your drive radius. A campaign is mostly defined by what it refuses to bid on. Cut those first and the same money buys better calls.
The short version
Two campaigns, two ceilings, both derived from your own ticket values. A budget that follows the season. And a list of what you will not bid on, written before the first dollar goes out. Do that and you will know what a call costs in each half of the business, which is the number that decides everything else.