The economics of the no-cost visit
Most companies will look at your system at no charge, and it's worth being clear-eyed about what that visit is: a sales appointment. The technician's hour gets paid for either way — on a no-cost visit, it's paid for by whatever you buy at the end of it. That's not an accusation of bad faith; it's just the incentive structure. Your doctor charges for the exam and your mechanic charges for the diagnostic hour for the same reason: it keeps the diagnosis independent of the sale.
What a paid diagnostic should include
Instruments, not a flashlight. Our $149 System Evaluation measures static pressure, airflow at the registers, temperature split, refrigerant charge against measured superheat and subcooling, and combustion on gas equipment — and ends with the Home Comfort Report: every reading in plain language with a prioritized plan. There's a sample report on this site so you can judge the deliverable before you spend a dollar. And it carries a simple promise: if we can't show you in writing what's wrong — or the numbers proving the system is healthy — the evaluation is free.
When you should skip it
A system under a year old should go back to the installer under warranty. A system that won't turn on at all may just need a breaker, a float switch, or a filter — check those first; it takes five minutes. And if you've already decided to replace no matter what, put the diagnostic money toward a Manual J load calculation instead, because sizing is where replacement decisions go wrong.