A distribution network operator, or DNO, runs the local electricity network that connects a UK home. Solar and battery inverters interact with that network, so the installer must follow the applicable connection rules. The common domestic routes are Engineering Recommendation G98 and G99.
The distinction affects whether installation can proceed before notification or needs permission first. It should be resolved before the contract becomes difficult to change.
Find the correct network operator
The DNO is determined by the property location, not by the electricity retailer shown on the bill. Some developments use an independent distribution network operator, or IDNO.
The installer can identify the network from the supply details and MPAN. Keep the operator name and application reference in the project file.
Changing electricity supplier does not change the physical network operator.
What G98 generally covers
G98 provides a simplified process for small, type-tested generation connected at low voltage. For a qualifying single-premises installation, the installer can generally install and commission the equipment, then notify the DNO within the required period.
Eligibility depends on the technical arrangement and aggregate capacity per phase, not the number of roof panels alone. The inverter's maximum export capability is central.
The installer must use compliant equipment, commission protection correctly, and submit complete notification documents.
When G99 is needed
Projects outside G98 generally follow G99. The installer applies before connecting, and the DNO assesses local network capacity, voltage rise, protection, phase arrangement, and other effects.
The DNO may approve the design, request changes, impose an export limit, identify reinforcement, or issue costs and conditions. Installation should not be energised contrary to the connection offer.
Allow additional time in the project schedule. A sales promise is not a DNO approval.
Panels, inverters, and capacity
Panel DC capacity in kWp can exceed inverter AC capacity in kW. This common oversizing does not mean the system can export the full panel rating at once.
The network assessment focuses on power-conversion equipment and its controllable output. Multiple inverters, microinverters, an AC-coupled battery, EV vehicle-to-grid equipment, or an existing generator can increase aggregate capacity.
Give the installer details of every existing or planned generator and storage device.
Batteries affect the application
A battery inverter can send power to the grid, even if the homeowner intends only self-consumption. Adding storage to existing solar can therefore change the connection assessment.
Hybrid inverters, AC-coupled batteries, backup interfaces, and grid-charging modes need accurate representation on the single-line diagram. Type-test records and control settings matter.
Read UK solar batteries and home storage before assuming a retrofit is purely behind the meter.
Export limitation schemes
An export limitation scheme controls combined generation so export at the point of connection stays within an agreed maximum. It can allow more panel or inverter capacity where local network export capacity is constrained.
The scheme must fail safely and meet the relevant engineering requirements. The DNO may specify approved equipment, settings, commissioning evidence, and ongoing conditions.
An export limit affects SEG revenue and may curtail generation when household loads and battery charging cannot absorb the available power.
Possible DNO responses
The network may offer the requested capacity, approve a lower export level, require phase balancing or three-phase connection, request further studies, or identify reinforcement work.
Costs and timescales vary with the site and local network. Ask who pays application fees, design changes, export-control hardware, reinforcement, metering, and additional visits.
Make the contract explain what happens if the requested design is not approved.
Documents to retain
Keep:
- G98 notification or G99 application.
- DNO acknowledgement, connection offer, and acceptance.
- Single-line diagram.
- Site plan and equipment schedule.
- Inverter and protection type-test evidence.
- Export-limitation details and settings.
- Commissioning and electrical test results.
- Final installed capacities per phase.
- Correspondence about later changes.
These records matter for SEG, service, battery additions, system extensions, fault investigation, and property sale.
DNO, MCS, and SEG are different
The DNO manages network connection. MCS certifies the installation route and provides recognised standards evidence. A SEG supplier pays for eligible measured exports.
Completing one does not automatically complete the others. A homeowner may have an MCS certificate but still need export metering and a SEG application. Likewise, DNO acceptance does not certify workmanship.
Use the MCS guide and SEG guide alongside the network documents.
Changes after installation
Tell a competent installer before adding panels, replacing an inverter with a higher-capacity model, installing a battery, changing export control, or removing equipment. The DNO may need a new application or notification.
Like-for-like replacement still needs accurate records. Protection settings and type-test compliance should not be altered casually.
The system owner also has ongoing responsibilities to maintain compliant operation and report relevant incidents or changes.
Questions before signing
- Who is the DNO or IDNO?
- Is the route G98 or G99, and why?
- What aggregate inverter capacity is declared per phase?
- Are existing solar, battery, or vehicle systems included?
- Is export limited, and at what value?
- Who submits documents and pays fees or reinforcement?
- What happens if the preferred design is refused?
- When will the final network records be supplied?
Common causes of delay
Incomplete forms, mismatched capacities, missing type-test evidence, unclear diagrams, unreported existing equipment, and design changes can slow review. Local network constraints may also require engineering assessment.
Provide complete site and equipment information early. Do not order non-returnable equipment around an unapproved G99 assumption unless the contract clearly allocates that risk.
A sound DNO application makes the network boundary visible before installation. That protects system performance, SEG expectations, safety, and future upgrades.