Key Insight
AOR attach rate is the structural diagnostic that separates HVAC service businesses with an organic upsell engine from those that bought their agreement count through marketing. Two shops with the same agreement count can have radically different acquisition economics underneath.
What the metric measures
Agreement on Repair (AOR) attach rate is the percentage of HVAC service repair calls in a period that are converted to a maintenance agreement during the call. The denominator is service repair calls; the numerator is repair calls that close with an agreement signed. A shop running 1,200 repair calls per year that closes 360 of them with an agreement runs a 30% AOR attach rate.
The ACCA (Air Conditioning Contractors of America) industry-standard minimum benchmark for the metric is 25%. The observed band in the 2026 atlas across functioning HVAC service businesses is 20–45%. Above 35% indicates a real organic upsell motion driven by trained technicians and a structured close on the call. Below 20% means the business is either not running an upsell process or is actively losing the agreement book to attrition faster than service calls regenerate it.
Why it separates organic from marketing-acquired growth
Two shops with the same 800 maintenance agreements look identical on the agreement-count line of the CIM. The structural difference shows up in AOR attach rate. Shop A runs 30%+ AOR attach — every service call generates incremental agreement growth, and the agreement book regenerates organically as customers cycle through repair events. Shop B runs 12% AOR attach and grows the agreement book through paid-search lead spend, direct mail, and HVAC trade-show acquisitions at $80–$140 of acquisition cost per agreement. Shop B's agreement count requires continuous marketing dollars to maintain; Shop A's regenerates from the existing service book at near-zero incremental cost.
Where to find the data
AOR attach rate is directly observable in ServiceTitan reporting under Membership Conversion and Opportunity Follow Up reports. Shops on FieldEdge, Housecall Pro, or comparable field-service systems have analogous reports. If the seller cannot produce the AOR attach rate from operating-system reporting, that is itself a diligence finding — it usually means the metric is below 20% and the upsell process is not formalized.
Shop A: 850 agreements, 32% AOR attach, marketing spend $14,000/yr. Shop B: 850 agreements, 14% AOR attach, marketing spend $96,000/yr to maintain the same book against agreement attrition. SDE band, before normalization, looks similar. After normalizing for the structural marketing cost required to hold Shop B's agreement count, the deals are not comparable.
Free Prescore — No Credit Card Required
Apply this to a real deal in minutes. No account, no commitment.