Three UK BESS assets secure ten-year voltage contracts

Three utility-scale battery assets have secured ten-year contracts to secure voltage services in the United Kingdom, in a tender run by the National Energy System Operator (NESO).

Battery energy storage systems (BESS) projects developed by Statera Energy, SSE Renewables and  Statkraft UK all secured contracts through NESO’s Voltage 2026 tender, with a fourth contract awarded to a reactor in South Yorkshire. The contracts are worth a combined total of GBP 83 million ($105 million) according to NESO, with the system operator claiming the contracts will save British consumers GBP 318 million across the ten-year period.

NESO has secured provision of 600 megavolt-ampere reactive (Mvar) in the 2026 tender. Reactive power services are how NESO ensures voltage levels in the system remain within a given range. It does this by instructing asset owners to absorb reactive power, decreasing voltage, or generate reactive power, increasing voltage. The tender focused on two regions in England, 400 Mvar was procured in the North of England with 200 Mvar in London.

Statera Energy’s 300 MW/600 MWh BESS in Thurrock, near London, will be the first to provide voltage services under the tender. From October 2025 the BESS will provide reactive power absorption capability for the local area.

In the north of England, a Statkraft UK BESS asset in Yorkshire is expected to provide voltage services from April 2026, while SSE Renewables’ 320 MW/ 640 MWh Monk Fryston BESS in Selby, North Yorkshire, is expected to join in early 2027. Statkraft has been approached for comment on the Yorkshire BESS.

Great Britain’s electricity system operator has stepped up procurement efforts on voltage services in recent years as it adapts to changing patterns of reactive power. NESO claims an increase in low carbon energy generation and a drop in minimum demand and power consumption at the distribution level has driven the change.

The 2026 voltage tender is the third introduced by NESO. Two previous rounds, Voltage Mersey and Voltage Pennines, procured additional reactive power across West Yorkshire and North East England for delivery between 2024 and 2034.