System integrator
Also known as: SI, BESS Integrator
A term used broadly in the BESS industry, but integration happens at three distinct levels.
A DC block integrator selects and integrates battery cells, modules, BMS, thermal management, and fire suppression into a containerized DC unit.
An AC block integrator integrates cells, modules, racks, BMS, thermal management, and PCS into a single AC-coupled unit with an LV AC busbar as the output interface.
A system level integrator takes responsibility for integrating AC blocks, plant controller, EMS, SCADA, protection systems, and grid interface into a coordinated, functioning plant.
In energy storage
System level integration is a technical function, not a company type. The responsibility can sit in two places: under an EPC contract, where the EPC contractor carries it by default (in-house or subcontracted), or with a developer doing direct procurement — buying DC blocks, PCS, controls, and other equipment from separate suppliers, thereby taking on system integration responsibility themselves.
EPC itself is a contract form, not a technical function. Many companies described as "system integrators" are more accurately DC or AC block integrators. The qualifier matters: the scope, risk, and competence required at each level are fundamentally different.
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