DC-coupled PV and BESS metering for settlement, efficiency and compliant project design

Project topologies: standalone, AC-coupled and DC-coupled

Why DC-coupled systems require DC-side metering

For settlement under UK market arrangements, solar PV and battery storage are treated as separate assets and must be registered as separate BMUs, even when co-located behind a single grid connection.

In DC-coupled systems, measuring energy solely on the AC side does not reflect the distinct energy flows associated with each BMU. Energy exchanged between the solar array and the battery occurs before DC-AC conversion and the associated conversion losses.

To correctly allocate energy to each asset for settlement, energy must therefore be measured on the DC side, upstream of the inverter. This allows solar generation, battery charging and battery discharge to be identified and accounted for in a way that aligns with the physical operation of the system.

This approach is consistent with National Energy System Operator (NESO) guidance on metering arrangements for DC-coupled co-located solar PV and battery energy storage systems (October 2025), which recognises the need for metering configurations that accurately reflect DC-side energy flows in co-located architectures.

Reference: NESO guidance (October 2025), DC-coupled co-located solar PV and battery energy storage metering

Settlement and revenue: why metering location matters

Revenue frameworks such as Contracts for Difference (CfD) and Power Purchase Agreements (PPA) rely on defined metered energy values. In addition, DC-coupled solar and battery projects may derive revenue from Capacity Market payments, battery arbitrage in wholesale markets, frequency response contracts, participation in the Balancing Mechanism, and Renewable Energy Guarantees of Origin (REGOs).

Settlement and revenue allocation are therefore directly linked to the location and configuration of metering equipment.

When energy is measured only after DC-AC conversion, settlement reflects the converted AC output rather than the underlying DC-side generation and storage flows. In DC-coupled projects, this can create a mismatch between how energy is physically generated and stored, and how it is accounted for commercially across different revenue streams.

For example, clear separation of solar export, battery charging energy and battery discharge is relevant not only for CfD and PPA settlement, but also for arbitrage optimisation, Balancing Mechanism participation and performance reporting under ancillary service contracts.

Addressing this requires settlement-aligned DC asset metering that reflects the architecture of the system.

In compliant configurations, DC asset meters operate in conjunction with the boundary point meter. This enables PV and battery energy flows to be measured behind the grid connection, while maintaining settlement compliance at the site boundary for CfD, PPA, Capacity Market, ancillary services and wider BSC requirements.

Historical barrier to DC-coupled deployment

While DC-coupled architectures have long been technically feasible, their deployment at scale was limited by the absence of certified DC metering solutions recognised for settlement.

Under the Balancing and Settlement Code (BSC), earlier Codes of Practice were written around AC metering of active and reactive energy and make no reference to DC meters. As a result, DC-side measurements could not be applied within recognised settlement frameworks.

This lack of settlement-recognised DC metering was one of the principal barriers to the commercial development of DC-coupled solar PV and BESS projects in the UK.

What changed with Code of Practice 11 (CoP11)

Code of Practice 11 (CoP11) introduced a framework under which DC metering can be used for settlement, provided defined technical, accuracy and compliance requirements are met.

This regulatory change transformed DC metering from an internal engineering or monitoring tool into a recognised settlement component. As a result, DC-coupled solar PV and battery storage architectures can now be designed in a way that aligns technical operation with commercial and regulatory requirements

Typical PV and BESS project scenarios

The CoP11-compliant DC asset metering configuration is intended for utility-scale solar PV and battery storage projects based on DC-coupled system architectures.

Typical use cases include:

• Co-located solar PV and battery storage projects with a shared grid connection
• Projects designed to capture DC-side energy flows between PV and BESS
• Schemes aiming to reduce conversion losses and improve overall system efficiency
• Projects requiring accurate separation of solar generation, battery charging and battery discharge for settlement or commercial reporting

Benefits and key considerations

Benefits

• Enables clear separation of solar generation, battery charging and battery discharge in co-located PV and BESS projects
• Supports DC-side settlement metering for DC-coupled architectures in accordance with CoP11
• Captures energy at source, ahead of DC-AC conversion losses
• Improves settlement accuracy, transparency and alignment with actual asset performance

Key considerations

• Applicable to projects using DC-coupled solar PV and battery storage architectures
• The meter must compensate for losses in order to align DC energy measurements with the defined settlement boundary of the project
• Asset metering configuration must comply with all requirements of Code of Practice 11