For C&I facilities, solar + BESS hybrids are increasingly driven by time-of-use tariffs, demand charge restructuring, and the need to shift consumption away from high-tariff periods. The technical challenge is building a dispatch logic that maximises bill savings while meeting the physical constraints of the battery and your facility's load profile.

This guide covers the four components of a correctly structured dispatch model for a C&I hybrid solar + BESS project.

  1. Define the objective function first Before building a dispatch model, define what it is optimising for. The objective function determines every subsequent design decision. For a C&I behind-the-meter or open access project, the objective is typically to minimise the monthly electricity bill — which means prioritising peak demand charge reduction over energy cost reduction, because demand charges (per kVA or kW of peak demand) are almost always the larger component of an industrial HT bill. A model built for utility-scale generation scheduling will perform poorly if applied to a C&I tariff structure.
  2. Build the battery degradation model into the dispatch Lithium-ion batteries degrade with each charge-discharge cycle, and the rate of degradation depends on the depth of discharge, the charge/discharge rate (C-rate), and the cell temperature. A dispatch logic that cycles the battery to 100% depth of discharge twice daily will exhaust the battery's cycle life in five to six years — not the ten to fifteen years assumed in the financial model. A correctly structured dispatch model incorporates a battery degradation model that limits depth of discharge (typically to 80% of nameplate capacity), manages the charge/discharge rate to stay within the manufacturer's recommended C-rate, and tracks the battery's State of Health (SOH) over time. The financial model must then be built on the degraded capacity curve — not the nameplate capacity — to correctly project energy yield and economic returns over the project life.
  3. Integrate the solar generation forecast A hybrid project's dispatch logic must know — at least one day ahead — what the solar generation profile for the following day is likely to be. This forecast determines how the battery is charged and when it is reserved for discharge. On a clear-sky day, the solar generation profile is highly predictable, and the dispatch logic can plan to fully charge the battery during the midday generation surplus and discharge it during the evening peak demand period. On a partly cloudy day, the profile is volatile, and the dispatch logic must hold battery reserve to compensate for generation shortfalls or accept reduced savings for that day.
  4. Model the grid code constraints Every BESS system connected to the grid must comply with the applicable DISCOM and state grid code requirements. Constraints that affect C&I dispatch logic include ramp rate limits, power factor requirements at the point of common coupling, and any obligations for reactive power management alongside active power dispatch.

A C&I hybrid solar + BESS project with a well-structured dispatch model — built on the correct objective function, incorporating battery degradation, integrating a generation forecast, and respecting grid code constraints — will consistently deliver against its savings model. One built on static, simplified assumptions will underperform within the first few years of operation.