ERCOT market structure — energy-only ISO, no capacity market

Reference notes

ERCOT is the only U.S. RTO/ISO that is both intrastate (Texas-only, escaping most FERC jurisdiction) and energy-only (no forward capacity auction). Scarcity revenue arrives instead through the Operating Reserve Demand Curve (ORDC). Texas is also the number-one U.S. destination for new hyperscale data centers in 2025, with ~52 GW of additional large-load growth projected by 2030 and 150+ GW already in the large-load interconnection queue. Mastering ERCOT mechanics is non-negotiable for any AWS Grid Code Compliance Manager with a Texas footprint. Use Next → to walk through ERCOT at a glance, the energy markets, the ORDC, the five ancillary-service products, and governance.

ERCOT at a glance

• Footprint: ~90 % of Texas load · Texas Interconnection (isolated from East / West)
• Customers: ~30 M Texans · 26 M metered points
• Peak: 85.5 GW (August 2024 record)
• Market: Energy-only — no capacity auction
• Regulator: Public Utility Commission of Texas (PUCT) + Texas Legislature · minimal FERC role
• Hyperscale context: ~52 GW projected to 2030 · 150+ GW in queue

Energy markets (DAM + RTM)

• DAM - hourly day-ahead SCUC with LMP at ~10 500 settlement points
• RTM - 5-minute SCED · co-optimized with ancillary services starting in 2025
• Load zones (4): HB_HOUSTON · HB_NORTH · HB_SOUTH · HB_WEST + hub/bus averages
• System-wide offer cap: $5 000 / MWh (lowered from $9 000 in 2021 via SB 3 / SB 7)
• Price floor: −$251 / MWh
• Settlement: Settlement Point Price (SPP) derived from LMP at the load's pricing node

The Operating Reserve Demand Curve (ORDC)

Because ERCOT pays no capacity payment, the market must signal scarcity through energy/ancillary prices alone. The ORDC, originally proposed by Prof. William Hogan and adopted by ERCOT in 2014, is the mechanism.

• Function: Adds a scarcity adder to the real-time energy price when reserves are tight
• Formula: Adder = VOLL × LOLP(reserves)
• VOLL: $5 000 / MWh (reformed down from $9 000 in 2021)
• Inflection points: reserves > ~7 GW ⇒ zero adder · reserves < ~2 GW ⇒ adder approaches VOLL
• Winter Storm Uri (Feb 2021): cap was administratively held at $9 000 for ~4 days ⇒ ~$50 B in incremental costs to load. Triggered SB 3 / SB 7 reforms.
• Hedging for hyperscale: bilateral PPAs · scheduled demand response · BTM gen / BESS

Ancillary services (5 products)

• Regulation Up / Regulation Down - minute-by-minute AGC modulation, FERC Order 755 Performance + Mileage settlement
• Responsive Reserve Service (RRS) - 10-second frequency response, includes load-resource RRS from large loads
• Non-Spinning Reserve - 30-minute response from offline generation + curtailable loads
• ERCOT Contingency Reserve Service (ECRS) - 10-minute response, introduced June 2023, $20-40/MWh avg clearing
• Large-load economics: a properly configured 100 MW data center can earn several $M / year selling Non-Spin + ECRS curtailable load to ERCOT; failed deployment triggers penalty + disqualification

Governance + Winter Storm Uri legacy

• Board: 8 governor-appointed directors + PUCT-appointed chair + 1 independent · all must be Texas residents (post-SB 3)
• Regulator: PUCT (3 commissioners, governor-appointed)
• Stakeholder hierarchy: TAC (Technical Advisory Committee) → ROS / WMS / PRS subcommittees
• Rule-change process: NPRR → PRS → WMS or ROS → TAC → Board → PUCT
• Uri reforms (2021): SB 3 / SB 7 mandated weatherization · PUCT redesigned ORDC · offer cap lowered · ECRS accelerated
• Large-load framework: PUCT §25.494 (2024) - Batch Zero process for loads ≥ 75 MW

Why it matters for the AWS Grid Code Compliance Manager role

ERCOT moves at a different cadence than the FERC-jurisdictional RTOs. The PUCT and the Texas Legislature can change market rules on much shorter timescales than FERC. Mastery of ERCOT governance, the NPRR pipeline, ORDC dynamics, and the §25.494 large-load framework is the bedrock for navigating any AWS Texas footprint from siting through energization.