Trade capture, volume aggregation, and mark-to-market

Power Trading - Calculating PNL and MTM

ETRM systems capture and value energy trades. This illustration shows how a German power trade (EEX, base + peak) is captured, how volume is aggregated to MWh, and how mark-to-market and P&L are calculated when prices change.

EEX European Energy Exchange
Base + Peak German power products
EUR/MWh Price unit
MTM Mark-to-market

Base load vs peak load

Base load is volume in MW that applies 24 hours per day, every day of the delivery month (including weekends and holidays). It is round-the-clock power: the same MW quantity is delivered in every hour. Base products are typically cheaper per MWh because they include off-peak (night and weekend) hours when demand and prices are lower.

Peak load is volume in MW that applies only during peak hours (e.g. 8:00–20:00 on weekdays only). Here, peak = 12 hours per day on weekdays only (weekends excluded). Peak products are more expensive per MWh because they cover high-demand periods when prices are higher.

Why the difference matters: Traders and offtakers buy base when they need continuous supply (e.g. industrial processes) and peak when they only need power during business hours. ETRM must treat them as separate volume streams with different hours and prices, then aggregate to MWh for valuation.

ProductHours/dayDaysTypical price
Base24All daysLower EUR/MWh
Peak12Weekdays onlyHigher EUR/MWh

Trade details & volume aggregation

ETRM requires: Trade ID, Trade date, Delivery period (e.g. Feb-2025), Product type (monthly base + peak), Exchange (EEX), and Buy/Sell. Volume aggregation converts MW to MWh: Total volume (MWh) = MW × Hours per day × Days. Base: all days × 24h × Base MW. Peak: weekdays × 12h × Peak MW. Example (Feb 2025: 28 days, 20 weekdays): Base 50 MW → 28×24×50 = 33,600 MWh; Peak 30 MW → 20×12×30 = 7,200 MWh; Total 40,800 MWh.

Mark-to-market (MTM)

Trade value = Trade price × Volume (MWh). Market value = Market price × Volume (MWh).

MTM formula
For a BUY trade: MTM P&L = (Market price − Trade price) × Volume (MWh)
Positive P&L = market price went up (good for buyer). Negative P&L = market price went down (bad for buyer).
For a SELL trade: MTM P&L = (Trade price − Market price) × Volume.

MTM is computed per component (base, peak) and then summed.

Price change & P&L impact

Scenario: Market prices change after trade execution (e.g. T+7 days). Original position (T0): Market price = Trade price → MTM P&L = 0. New market prices (T1): Base and peak prices move up or down. Updated MTM: Reapply the formula with new market prices; P&L changes. P&L change (delta): New total MTM P&L minus original; this shows the period P&L movement.

Limitations

MTM here is theoretical (no funding, collateral, or discounting). Volume aggregation assumes fixed days/hours (e.g. standard weekday definition for peak); calendar and product definitions can vary by exchange. Real ETRM systems also handle settlements, nominations, and risk limits.