A G99 application is the formal request a generator makes to its Distribution Network Operator (DNO) to connect a power-generating system to the UK distribution network, under Engineering Recommendation G99. For commercial solar PV, a G99 application is required wherever the installation exceeds the G98 threshold of 16A per phase, which covers the large majority of commercial and industrial arrays.
G99 application vs G98 notification
G98 is a simple notify-and-connect route for the smallest systems. A G99 application is an apply-and-await-approval process: the DNO assesses whether the local network can accept the proposed generation before connection is permitted. Sub-50kWp commercial systems and all larger arrays sit under G99.
The G99 application process
The connection applicant submits the technical detail the DNO needs to assess the connection: proposed generation capacity, inverter make and model, protection settings, and a single-line diagram. The DNO reviews this against local network capacity and either issues a connection offer or, where the network is constrained, sets out reinforcement requirements or export-limiting conditions. Defined response timescales apply, though larger systems in constrained network areas can take longer.
Where structural sign-off fits the G99 application
A G99 application is an electrical-connection process, but lenders, PPA providers and project sponsors increasingly expect the structural evidence pack to sit alongside it in due diligence: an engineer-signed structural roof-loading appraisal confirming the roof can carry the array. Above the 50kWp MCS threshold, the same Eurocode-verified structural assessment governs larger commercial and industrial arrays. Solar Surveys provides the structural side; the G99 application itself is handled within the project's electrical scope.