Introduction
Most people involved in California construction have heard of HERS Raters. Fewer are familiar with Acceptance Testers — even though acceptance testing is a required step on most nonresidential construction projects and many multifamily buildings in California.
If your project involves commercial construction, tenant improvements, or multifamily buildings of a certain size or complexity, you will likely need a certified Acceptance Tester before you can close out your permit. This post explains what acceptance testing is, what an Acceptance Tester does, which projects require it, and how to find a certified tester for your project.
What Is Title 24 Acceptance Testing?
Acceptance testing is a functional verification process required under California's Title 24 Part 6 Building Energy Efficiency Standards. The purpose is to confirm that specific building systems — particularly lighting controls and HVAC controls — are not just installed, but are installed correctly and operating as intended.
Unlike HERS verification, which focuses on residential buildings and emphasizes diagnostic measurements (like duct leakage or refrigerant charge), acceptance testing is primarily about functional performance. Does the occupancy sensor actually turn the lights off when the room is empty? Does the economizer open and close correctly? Does the demand control ventilation system respond to CO₂ levels appropriately?
These are not things you can verify by looking at the equipment. They require someone to actually test the system — to walk through the space, simulate occupancy, and observe whether the controls respond as designed.
What Does an Acceptance Tester Do?
A certified Acceptance Tester performs functional testing on required building systems and documents the results on the appropriate California Energy Commission acceptance testing forms.
For lighting controls, acceptance tests verify that occupancy sensors (vacancy sensors and occupancy sensors) activate and deactivate lighting correctly, daylighting controls (automatic dimming systems near windows and skylights) respond to changing light levels, shut-off controls operate as required, and exterior lighting controls turn off or dim during daylight hours.
For HVAC, common acceptance tests include economizer controls (verifying that the economizer opens to bring in outside air for free cooling when outdoor conditions are favorable — this is one of the most frequently required and most commonly failed acceptance tests), demand control ventilation (verifying that CO₂-based ventilation control systems modulate outside airflow based on actual occupancy), supply air temperature reset, and hydronic system controls.
Depending on the project scope, additional acceptance tests may be required for fault detection and diagnostics systems, automatic demand shed controls, and refrigeration system controls in commercial kitchen and food service applications.
When Is Acceptance Testing Required?
Acceptance testing is required under Title 24 Part 6 for new nonresidential construction (virtually all new commercial buildings require acceptance testing for applicable lighting control and HVAC control systems), additions and alterations to nonresidential buildings when the scope of work includes systems that trigger acceptance testing requirements, multifamily buildings (high-rise multifamily, four stories and above, is classified as nonresidential under Title 24 and generally requires acceptance testing), and tenant improvements that include new or modified lighting or HVAC systems.
Acceptance testing is not required on single-family residential projects, which are instead covered by HERS verification.
The specific tests required on a given project are determined by the compliance documentation. Review the CF1R to identify which acceptance tests are required for your project.
Who Can Perform Acceptance Testing?
Acceptance Testers in California must be certified through a CEC-approved Acceptance Test Technician Certification Provider (ATTCP). An Acceptance Test Technician (ATT) is an individual certified to perform acceptance tests who must have at least three years of verifiable professional experience in mechanical controls and systems. Certification for mechanical ATTs has been required statewide since October 1, 2021.
An Acceptance Test Employer (ATE) is a company or firm that employs certified ATTs and is responsible for quality control and appropriate supervision of ATTs on projects.
Both the individual technician and their employer must be certified. When hiring an acceptance tester, verify that both the technician's ATT certification and the company's ATE certification are current.
Some HERS Raters also hold ATT certification, allowing them to perform both HERS verification and acceptance testing on applicable projects. However, the two roles have distinct certification requirements and not all HERS Raters are certified Acceptance Testers.
Acceptance Testing vs. HERS Verification: Key Differences
Acceptance testing focuses on functional performance of controls and is performed by a certified Acceptance Test Technician, primarily for nonresidential and high-rise multifamily projects. Key systems tested include lighting controls and HVAC controls.
HERS verification focuses on diagnostic testing of systems like ducts, refrigerant, and airflow. It is performed by a certified HERS Rater, primarily for residential and low-rise multifamily projects. Key systems include duct systems, HVAC equipment, insulation, and windows.
Both types of verification are required on many projects — particularly high-rise multifamily buildings — and both must be completed before permit final.
Conclusion
Acceptance testing is a required part of Title 24 compliance for most nonresidential construction in California. A certified Acceptance Tester verifies that lighting controls, HVAC controls, and other systems actually function as required — not just that they were installed. The results are documented on CEC acceptance testing certificates that must be on file before a project can receive final permit approval.
If your project involves commercial construction, tenant improvements, or high-rise multifamily, acceptance testing is almost certainly in scope. Start by reviewing your CF1R to identify which tests are required, then connect with a certified ATT/ATE early in the construction process.