An interconnector is a high-voltage cable, usually laid under the sea, that joins the electricity grids of two countries. Power flows towards whichever market has the higher price at that moment, so the same link can import in the evening and export a few hours later.
How it works
Most interconnectors use high-voltage direct current (HVDC), which loses less energy over long subsea distances than alternating current. A converter station at each end turns the power back into alternating current for the local grid. Traders book capacity on the link, and flows follow the price difference between the two markets.
Great Britain’s links
| Measure | Figure |
|---|---|
| Interconnectors in operation | 10 |
| Total operating capacity | 10.3 GW |
| Countries connected | Norway, Denmark, Netherlands, Belgium, France, Northern Ireland, Republic of Ireland |
| Imports, year to September 2025 | 43 TWh |
| Exports, same period | 12 TWh |
| Under construction | 1.4 GW to Germany |
Source: GOV.UK, March 2026.
Cap and floor
Since 2014 most new links have been built under Ofgem’s cap and floor regime. It sets a maximum and a minimum level of revenue the owner can earn each year over 25 years. Revenue is checked against those levels, normally every five years. Anything above the cap is paid back to GB consumers; if revenue falls below the floor, consumers top it up. The aim is to limit the developer’s exposure to market prices without guaranteeing a return.
Ofgem has opened three application windows. Projects approved in principle in the third include links to Germany, Northern Ireland and the Republic of Ireland; in 2025 Ofgem extended their deadline to start operating to the end of 2035.
Why it matters
Interconnectors let Britain import power when wind is low and sell surplus power when it is high, which reduces the need for backup plants at home. They also mean that prices and supply in Britain depend partly on neighbouring markets.
Read more: Morocco–UK subsea power link brought into the national planning regime.