Grid connection design
Designing the connection between a new infrastructure load (EV, datacentre, industrial) and the electricity network.
Grid connection design is the engineering work that gets a new electrical load connected to the network. For EV charging hubs above the threshold where existing supply is insufficient, this is the path that determines timeline and cost more than any other element of the project.
Why grid connection is on the critical path
Most EV hubs above ~150-200 kW total load require new or upgraded grid connection. The connection process is regulated and slow — months for routine connections, years for connections requiring substantial network reinforcement.
Three factors put grid connection on the critical path:
1. Network operator timelines are largely fixed. UK DNOs operate within Ofgem-regulated timeframes for connection responses, but the actual physical work — substation builds, line upgrades — runs to its own schedule. US utility timelines vary by utility; some are responsive, others have multi-year backlogs.
2. Cost is highly site-specific. Two sites 200 metres apart can have wildly different connection costs depending on which feeder they’re closest to and where the nearest substation has capacity.
3. Reinforcement requirements stack. Where the local network needs upgrading to support the new load, that upgrade triggers further upstream upgrades, and so on. Cost can multiply through several levels of network.
What grid connection design covers
A complete engagement covers:
- Feasibility assessment — connection options at the site, network operator constraints, indicative cost ranges
- Application support — the technical documentation network operators require to provide a quotation
- Single line diagrams — site supply, substation arrangement (if private), interface with operator network
- Protection design — protection coordination on the customer side, interface with operator protection
- Substation specification — where a private substation is required, the design specification
- Transformer sizing — kVA rating, vector group, cooling
- Cost model — across connection scenarios, with sensitivity analysis
- Programme — aligned with network operator response times and physical work schedules
Markets and processes
UK — DNO and IDNO routes. UK projects can connect via the licensed Distribution Network Operator (DNO) for the area or, for larger commercial connections, via an Independent Distribution Network Operator (IDNO) that builds and operates the local network. Choice depends on cost, timeline, and operating model preferences.
DNO connection process runs through standard application stages — Connection Offer Process, Connection Agreement, Construction. Timelines run to specific Ofgem-regulated SLAs. Costs split between contestable and non-contestable elements.
US — utility-by-utility interconnection. US connection runs through the relevant utility’s interconnection process. Each utility has its own application forms, technical requirements, and timeline expectations. Some states have streamlined processes (California’s Rule 21 for distributed energy); others run slower.
EU markets — country-by-country, with each market having its own distribution network operators, application processes, and standards.
What we deliver
A typical engagement produces:
- Connection feasibility report — options at the site, indicative costs, expected timeline
- Application package — completed forms, technical schedules, supporting documentation in the format the operator requires
- Technical design — single line diagram, protection design, substation spec where applicable
- Cost model — connection cost scenarios, capex split, contingency
- Programme — connection works schedule aligned with project timeline
Inputs we need
A productive grid connection engagement runs on:
- Site address and proposed load — exact site, total demand, simultaneous demand profile
- Use case — EV hub, datacentre, industrial process, retail
- Operating posture — preferred connection voltage, time-of-use considerations, future expansion plans
- Schedule — when does the load need to be live
- Existing supply — what’s at the site already
Common pitfalls in outsourced grid connection work
Optimistic cost estimates. Connection costs depend on site-specific network conditions. Generic estimates that don’t reflect actual feeder loading and substation headroom produce numbers that underestimate by 2-5x. We build estimates with explicit assumptions about network conditions.
Underestimated timeline. Project programmes that assume rapid grid connection get blindsided when reinforcement is needed. We surface realistic timeline ranges including reinforcement scenarios.
Application packages that trigger questions. Operators send technical questions back when applications are incomplete or unclear. Each round of questions adds weeks. We produce applications that anticipate the operator’s review process.
Customer-side protection coordinated without operator-side awareness. Protection that doesn’t interface cleanly with operator-side protection produces commissioning failures. We coordinate with operator engineering teams during design where the project warrants it.
Typical timelines
Design and application work:
- Simple connection — 2-4 weeks for application package and supporting design
- Complex multi-megawatt site — 6-12 weeks
- Reinforcement scenarios — additional 2-4 weeks for analysis and operator engagement
Operator response and physical works:
- UK DNO standard connection — 13-week response per Ofgem, plus physical works (months to years)
- UK IDNO — sometimes faster, depending on the IDNO and site
- US utility — varies dramatically; some 30-60 days for simple, multi-year for complex
- Reinforcement — adds substantial time depending on network operator’s plans for the area
How we deliver
Grid connection work runs onshore-led for engagement with network operators and code interpretation. Production drafting (single line diagrams, application package documentation) runs offshore with onshore QA. Senior engineers handle network operator engagement directly.
Talk to us about a grid connection
Tell us the site, the load, the use case, and the timeline. We’ll scope and price within two business days for typical sites; reinforcement scenarios and complex multi-megawatt sites usually warrant a scoping call.
Typical deliverables
- Connection feasibility assessment
- Single line diagrams and protection design
- DNO / IDNO / utility interconnection application support
- Substation and transformer specification
- Cost model across connection scenarios
- Programme alignment with network operator timelines
Who buys this
Project owners adding significant new electrical load to the grid — typically EV charging hubs, datacentres, industrial sites, or large commercial developments.
Talk to us about delivery options
Tell us what you need delivered, what your timeline is, and what format the downstream team needs the output in. We'll come back with scope, price range, and proposed approach.