Q4Restructured Power System

Transmission pricing addresses the fundamental challenge of fairly and efficiently allocating the substantial fixed cost of the shared transmission network among the many different generators and loads that use it, given that transmission is a natural monopoly requiring some form of regulated cost recovery rather than pure market-based pricing for the network infrastructure itself.

Rolled-in (postage-stamp) pricing: as discussed earlier, this method averages the entire embedded transmission cost across all users through a common per-unit tariff, regardless of actual usage pattern or location — simple to administer but not cost-reflective of individual users' actual impact on the network.

Contract path method: allocates transmission cost based on a notionally defined 'contract path' between the specified point of injection (generator) and point of withdrawal (load) for a given transaction, even though actual physical power flow (governed by the laws of physics, following the path of least impedance across the entire interconnected network) may differ substantially from this notional contractual path — simple conceptually but can significantly misrepresent the actual physical burden a transaction places on the network.

MW-mile method: a more cost-reflective incremental pricing approach that allocates transmission cost based on the actual (or calculated, via power-flow studies) usage of each individual transmission line by a given transaction, measured as the product of the power flow attributable to that transaction (in MW) and the length of each line segment used (in miles/km), summed across all lines affected — better reflects the actual physical burden different transactions place on different parts of the network, though computationally more complex to implement, particularly for allocating flows in a meshed network where multiple parallel paths exist.

Locational Marginal Pricing (LMP)/nodal pricing: as discussed in earlier answers, this approach does not allocate transmission cost as a separate charge at all, but instead embeds the transmission (congestion and loss) cost directly into the energy price at each node, so that the price difference between any two nodes automatically reflects the marginal transmission cost (congestion plus marginal losses) of moving power between them — this is generally regarded as the most economically efficient and cost-reflective transmission pricing approach, since it derives directly from the physical, real-time operating conditions of the network rather than from any simplified notional allocation method, though the fixed (embedded) network cost still requires separate recovery (typically through rolled-in-style transmission access charges) since LMP alone recovers only the variable congestion/loss cost component, not the fixed capital cost of the network.

Trade-offs in transmission pricing method selection: simpler methods (rolled-in, contract path) are easier to administer and provide greater price predictability/stability for market participants, but provide weaker (or even actively misleading) economic signals for efficient generation siting and transmission investment; more cost-reflective methods (MW-mile, LMP) provide much stronger, more accurate economic signals but are computationally more complex and can create greater price volatility and locational cost disparities that may raise equity concerns for certain user groups. In practice, most restructured electricity markets today use a hybrid approach: LMP (or a similar nodal/zonal marginal pricing method) for real-time energy market dispatch and short-term congestion/loss cost signaling, combined with a separate rolled-in or postage-stamp-style transmission access charge to recover the underlying fixed network infrastructure cost, attempting to capture the efficiency benefits of marginal pricing for operational decisions while retaining administrative simplicity and equity for the larger, embedded fixed-cost recovery component.