XBID (Cross-Border Intraday) is the shared European system that couples national intraday electricity markets, so an order placed in one bidding zone can match against liquidity in another. It operates under the Single Intraday Coupling (SIDC), and it is what turns a set of separate national order books into one connected European intraday market. The coupling is physical as well as financial: an order can only match across a border while transmission capacity remains available on that border, so cross-border trading is always bounded by the grid. Traders do not connect to XBID directly; they reach the coupled market through their own exchange's trading system. On EPEX SPOT, that system is M7, which carries both the coupled order book and the cross-border capacity data that constrains it.
What is the difference between XBID and SIDC?
SIDC (Single Intraday Coupling) is the European market-coupling arrangement; XBID is the shared system that implements it. In day-to-day trading language the two are used almost interchangeably: a desk "trading XBID" is trading the coupled European intraday market that SIDC defines. What matters practically is the same under either name: national intraday order books are connected, and orders match across borders whenever price and transfer capacity allow.
How does cross-border matching work?
Orders match across a border the same way they match domestically, by price and time, with one extra constraint: available transfer capacity. When an order in one bidding zone crosses with an order in another, the trade consumes transmission capacity in that direction on the border between them. Capacity is tracked per direction and per delivery interval, and each interval's capacity expires with the interval itself. While capacity remains, the two zones behave like one book; when it runs out in a direction, matching in that direction stops for that interval and the zones' prices are free to separate. That is why a cross-zone price spread is only a tradable opportunity if the capacity that would have to carry it actually remains.
What is available transfer capacity (ATC)?
Available transfer capacity is the amount of cross-border transmission capacity, in megawatts, still available for trading between two delivery areas in a given direction for a given delivery interval. It is directional: from a zone's point of view, export capacity (flow out of it toward a neighbour) and import capacity (flow into it) are tracked separately, and they are consumed independently as cross-border trades execute. Because ATC is the binding constraint on cross-border matching, a desk that trades zone-to-zone spreads needs to read prices and capacity together: a spread against an exhausted border is not an opportunity, it is two disconnected markets.
How does XBID relate to EPEX SPOT M7?
M7 is the trading system through which EPEX SPOT participants access the coupled intraday market; there is no separate XBID screen or session. The coupled order book a desk sees in M7 already reflects cross-border liquidity where capacity allows, and M7 also relays the hub-to-hub capacity data and watches its own link to XBID, signalling when that link drops. For what M7 is and how a desk connects to it, see What is EPEX SPOT M7?
How does Voltnir handle cross-border capacity?
Voltnir maintains the exchange's hub-to-hub capacity data as a live ATC matrix: for every ordered pair of delivery areas and every delivery interval, the import and export capacity in megawatts, with each entry enriched with the best bid and ask on both sides of the border so the cross-zone spread reads straight off one feed. The feed is opt-in per deployment, because not every desk trades cross-border, and the capacity connection's own health is served alongside the data: a stale or missing matrix is visible as such, never silently presented as current. The matrix is queryable over the API, there is a live subscription for it, and the bundled trading terminal renders it as a pan-and-zoom map of Europe coloured by opportunity: the directional spread gated by the capacity that would have to carry it. The full detail is in the cross-border section of the features page.
Frequently asked questions
Is XBID a separate market I need to join?
No. XBID couples the national intraday markets you already know; you reach it through your exchange membership and its trading system. On EPEX SPOT that system is M7, and a desk trades the coupled market through the same session, order types, and order book it uses domestically.
What limits cross-border matching?
Available transfer capacity (ATC): the megawatts of transmission capacity available in a given direction between two delivery areas for a given delivery interval. While capacity remains, orders across that border can match; once it is used up in a direction for an interval, orders in the two zones can no longer match each other for that interval.
Do quarter-hour products trade cross-border?
Yes. Since October 2025 each day splits into 96 quarter-hour products across the coupled European intraday markets, and cross-border matching applies per delivery interval: each 15-minute window has its own transfer capacity, which expires with the interval.
Does Voltnir support XBID?
Yes, as an opt-in feed. Voltnir relays the exchange's hub-to-hub capacity data into a live ATC matrix, enriches each entry with the best bid and ask on both sides of the border so the cross-zone spread reads straight off one feed, and surfaces the capacity connection's own health so a stale matrix is never silently presented as current.