New York City (Zone J) and Long Island (Zone K) offer the highest Top-Bottom (TB) spreads in NYISO.

Between 2023–2025, Zone K's mean daily TB4 spread of $254/MW-day was 30% higher than Zone J's $195/MW-day spread and 144% above the statewide average. On extreme days, the gap widens further. Zone K's maximum spread reached $11,642/MW-day in June 2025, 78% higher than Zone J's peak.

These spreads reflect transmission constraints that limit imports during peak demand. Zone K's constraints ease by 2030 when Propel NY connects. Zone J's persist through 2034 as retirements outpace additions.

Key Takeaways

• Zone K's mean spread is 30% higher than Zone J's but the zones have fundamental differences in their arbitrage opportunities.
• Zone J will lose nearly 1 GW of fossil capacity by 2030. Transmission and offshore wind do not fully replace local generation during peak periods due to capacity accreditation rules.
• Long Island’s transmission security deficits close by 2030 when Propel NY connects. Zone J's persist through 2034.
• Long Island faces 1–4 hours of transmission security deficiency per summer peak day. New York City faces 6–13 hours, creating longer windows for arbitrage.

Zone K offers higher spreads, while Zone J is likely to have more sustained spreads

Long Island (Zone K) delivers higher spreads over a narrower window. New York City (Zone J) delivers lower spreads across a longer multi-year structural deficit.

Both zones are transmission-constrained. When local demand outstrips supply and import capability, real-time prices spike and batteries with available capacity can capture multi-hour arbitrage.

​Under Status Quo, Zone J faces 6–13 hours of transmission security deficiency per summer peak day through 2030, with demand exceeding supply by 500–1,130 MW. Zone K's deficiency window is shorter: 1–4 hours, with shortfalls of 39–254 MW. During these intraday deficiency events, NYISO would have to unlock emergency generation to meet local demand to avoid firm load shed.

Even with all planned projects online, Zone J remains at risk: 68 MW over 5 hours in 2029, growing to 148 MW over 6 hours in 2030. Zone K's margins turn positive once Propel NY connects.

This difference in scarcity duration explains why Zone J's spread potential persists longer.

​​Zone J's projected 6–13 hour deficiency windows create similar conditions for sustained spreads. Zone K's 1–4 hour windows offer higher but more acute spikes.

How long does the opportunity last for new BESS?

​Both zones are transmission-constrained. When margins fall near zero, real-time prices spike and batteries with available capacity can capture multi-hour arbitrage. The question is how long those constraints persist in each zone.

Subscribers to Modo Energy’s Research can read the full article to explore whether the drivers of these spreads will change and how long the opportunity window for BESS will remain open.

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Zone J’s aging generators widen TB spreads at peak load hours

NYC's steam turbine fleet age averages 66 years, while the broader statewide fossil fleet age averages 43 years. By contrast, ISO-NE's fleet age averages 29 years and ERCOT's averages 32 years.

By 2030, NYC will lose nearly 1 GW of fossil capacity to retirements and climate standards. Transmission and offshore wind do not fully replace this capacity. Offshore wind receives only 10% accreditation at summer peak. New transmission links are unlikely to support the system during peak load events, either because of limited export capacity or a lack of contractual obligations (CPHE only provides power during the summer). Serving load in a transmission-constrained zone requires local supply: generation, storage, or demand response physically inside the constraint.