History: how the daily spread has moved over the years

The Price Volatility view reads the same record month by month for six bidding zones, with the hours below zero beside the spread.

What a widening spread is telling you

The daily spread, which traders call TB1, is the day's widest gap: the most expensive hour minus the cheapest, in euros per megawatt-hour. It measures how much the price moved within a single day, which is a separate question from how expensive that day was. A cheap day can be a wide one, when a sunny midday drives the price towards zero and the evening peak brings it back up. An expensive day can be flat, when a cold still week keeps the same kind of plant setting the price around the clock.

Solar is what has done most to widen the German spread. Every gigawatt added deepens the midday trough without touching the evening peak, so the distance between them grows. That distance is the revenue a battery or any other flexible user can earn.

Three ways to read the same data. Dragging across the long series zooms into a stretch, which is how a storm week or a price shock is examined in isolation. The seasonal curve folds every year onto 12 months and answers which part of the year runs wide. The year-on-year chart averages each calendar year into one figure and shows the trend the daily noise hides.

In October 2025 the German day-ahead market moved from hourly to quarter-hour prices, so the underlying series changes resolution partway through. Wattlas averages the quarter-hour prices back to hourly across the whole history before computing any spread, which keeps the years comparable. Finer resolution would show a slightly wider spread in the later period from arithmetic alone, and the hourly series keeps that effect out of the trend.