Illinois’ Clean and Reliable Grid Affordability Act (CRGA) requires the state’s utilities to compensate distributed batteries in three ways. They must offer a rebate of up to $300/kWh, net imports and exports hourly at retail prices, and pay an additional incentive for discharging on summer evenings.

Illinois’ two largest utilities, ComEd in PJM and Ameren in MISO, built compliant programs on top of their existing tariffs and market rules. As a result, the revenue opportunities for BESS owners diverge between the two.

Excluding the rebate, a 4 MW, 4-hour battery on ComEd’s distribution network may earn $108k/MW-yr in 2030. That matches PJM’s wholesale opportunity and only assumes the operator captures half of the credits available for exporting at system peaks. On Ameren’s network, the same battery would earn about $2k/MW-yr under the CRGA. In MISO’s wholesale market, it would earn $80k/MW-yr.

The gap comes almost entirely from peak credits, which ComEd offers and Ameren does not. Ameren also bills demand charges on overnight charging, which squeezes energy arbitrage.

Key takeaways

• Peak credits drive ComEd’s distributed BESS revenues. Exports at PJM and ComEd peaks turn capacity and transmission charges into credits worth about $100k/MW-yr at 50% capture, 95% of ComEd’s premium above Ameren.
• A 4-hour distributed battery in ComEd matches the revenues of its wholesale equivalent at 50% peak credit capture. A 2-hour battery needs just 11% peak capture.
• Ameren pays no peak credits and applies demand charges to overnight charging. On today’s tariffs, batteries would make far more in MISO’s wholesale market.
• Net-metered ComEd sites can add PJM regulation today, though the route is untested for stand-alone batteries. Ameren has no defined route into MISO’s ancillary markets.
• The Illinois Commerce Commission (ICC) is due to rule on Ameren’s net metering tariff around February 6, 2027. The commission’s own staff have argued it lacks the power to order peak credits.

ComEd pays batteries for exporting at the peak; Ameren says it can’t

Both utilities set a customer’s capacity and transmission charges from its load during the summer peaks. In ComEd, net-metered customers’ load in those hours can go negative by exporting, so a battery discharging through those hours earns a credit instead of paying a charge.

Ameren does not offer this. It has told the ICC that a customer’s capacity contribution “” and MISO’s transmission tariff cannot bill negative demand.