Short answer

• Adoptable means the network operator takes it over. Ownership and maintenance pass to the DNO or IDNO.
• It is built to the operator’s specification, not to the designer’s preference.
• It is adopted on completion, after the operator’s inspection and QA.
• Everything downstream of the ownership boundary stays private and is designed to BS 7671.

DNO and IDNO

Both are licensed operators of distribution networks. The difference is which network they own.

What makes an asset adoptable

• Designed and built to the operator’s published specification: cable types and jointing, duct sizes and arrangement, substations and switchgear, access and clearances.
• Constructed by the DNO, or by an Independent Connections Provider (ICP) accredited to build to DNO standards.
• Inspected and adopted by the DNO or IDNO on completion, when ownership and long-term maintenance pass to the operator.

Who builds it: contestable and non-contestable work

A new connection is open to competition. The work splits in two.

The ownership boundary

An adoption agreement and a connection agreement fix two points: the point of connection to the existing network, and the network ownership boundary.

The boundary is where the adopted asset ends and the site’s private installation begins. On an IDNO scheme it commonly sits at the LV fuse cabinet at the transformer. Downstream of it the cables, distribution boards and final circuits are private assets, owned and maintained by the client or landlord.

Adoption is also commercial

An IDNO usually pays an asset value to adopt the network, funded by its future use of system charges. That payment can offset the developer’s connection cost, and it is the main reason a new network is routed to an IDNO rather than the host DNO.

Ownership is the first design decision.

An adoptable run conforms to the DNO or IDNO specification, so the network stays maintainable for decades. The operator sets the duct size, the separation, the materials and the access. BS 7671 grouping and derating freedoms do not apply to it.

A private, landlord supply on the same site is designed to BS 7671. On a single development you routinely have both, and the ownership boundary is the line between them.

Related terms

• DNO (Distribution Network Operator)
• IDNO (Independent Distribution Network Operator)
• ICP (Independent Connections Provider)
• Point of connection
• Contestable works
• Landlord supply
• BS 7671

Sources. Energy Networks Association and DNO connections guidance: competition in connections, ICP construction to DNO specification, adoption of the network on completion, and non-contestable work retained by the DNO. UK Power Networks EDS 08-0113, network ownership boundary arrangements for IDNO connections. Each DNO and IDNO publishes its own adoptable design specification, which applies to the adoptable works. BS 7671 applies to the private installation downstream of the ownership boundary.