Allocation Rules Gate Carbon-Price Thresholds in Park-Level Source–Grid–Load–Storage Systems: Institutional Trade-Offs in Six Chinese Provincial Reform Scenarios

Whether a carbon price changes how energy users dispatch their own generation is usually treated as a technical question rather than an institutional one. This paper asks when, and under what institutional conditions, a carbon price crosses the technology-substitution threshold in demand-side daily operation. We build a dispatch model of a park-level source–grid–load–storage system, solve it exactly as a mixed-integer linear program alongside a rule-based heuristic, and simulate six Chinese provincial electricity-market reform scenarios and a constructed high-carbon reference, with unit-commitment, multi-day, Monte Carlo and auxiliary-regression checks. Emissions respond in thresholds rather than linearly, governed by an hourly switching-price distribution that is equivalent to an implied demand-side marginal abatement cost curve and coincides with the exact optimum. Three institutional gates—the allocation rule, the pass-through it implies, and the kinked free allowance—determine whether that curve operates, and none is the price level. The regression confirms that the price acts only through these gates, its effect on emission intensity reversing sign across allocation regimes. We read the rules as deliberate trade-offs sustaining industrial output and employment rather than as policy failure, and quantify the implicit subsidy they convey: a headline price of 100 CNY t−1 carries a revealed shadow value near 8. Allocation reform, not a higher price, restores the signal.