Batteries in SPP South had the potential to earn $12.3/kW-month in September 2026, or roughly $147/kW-year annualized. That was 14% below August's $14.2/kW-month.

Around the market, September's stress arrived in short evening windows rather than extended advisories.

SPP declared an Energy Emergency Alert Level 1 for its East balancing authority area from 6:56 p.m. to 7:30 p.m. CT on September 16, and real-time TB4 spreads that day reached $2,340/MW at the North Hub and $2,200/MW at the South Hub, against a South day-ahead spread of $316/MW. The day-ahead market did not price the evening tightness, so the month's sharpest prices cleared in real time.

In the West, SPP filed an interim market adequacy evaluation at FERC on September 4, after finding average available generation of about 4,700 MW against 9,204 MW of nameplate capacity between April and August. That shortfall is the backdrop to SPP West's lead in the revenue chart above.

To see how energy arbitrage briefly overtook ancillary services in the South Hub stack, read last month's August 2026 SPP benchmark report.

If you have any questions about our SPP research, please reach out to ovais@modoenergy.com.

Day-ahead TB4 spreads widened year-over-year at both eastern hubs

Day-ahead TB4 spreads reached $8.2/kW-month at the South Hub and $7.0/kW-month at the North Hub in September. The South widened 70% year-over-year and the North 26%. SPP West cleared $4.3/kW-month.