Most fleet electrification projects budget accurately for the chargers and underestimate everything else. The grid connection — getting sufficient power to the site — is consistently the item that triggers replanning. Not because it is unpredictable in principle, but because most fleet teams don't talk to the DNO until the charger specification is already written. By then, what they find out changes the project.
Why the Grid Connection Is Usually the Surprise
A diesel bus depot or logistics yard typically has a supply sized for office functions, maintenance equipment, yard lighting, and fuel systems. That's usually a 200–400A three-phase supply — somewhere between 140 kW and 280 kW at unity power factor. That supply is not unusual for the building. It's simply not what an electrified fleet needs.
A 24-bus depot with overnight charging needs 960 kWh delivered across an 8-hour window. At steady state, that's 120 kW — manageable on the existing supply. The problem is the peak load at shift changeover, when 12 buses return and want to charge simultaneously. At 150 kW each, that's 1.8 MW of simultaneous demand — ten times the existing supply.
The instinct is to request more power from the grid. The DNO process is where the instinct meets reality.
The DNO Application Process — Three Stages
The process for obtaining a new or upgraded grid connection from a UK Distribution Network Operator is structured in three distinct stages. Understanding what each stage costs and how long it takes is essential to building a realistic project programme — and to identifying where the most common delays occur.
Stage 1: Pre-Application Enquiry (4–8 weeks, £0–£5,000)
Before a formal application, most DNOs offer a pre-application service. The operator or their electrical engineer describes the site, the required import capacity, and the expected load profile. The DNO responds with an indicative connection cost and timeline.
Cost: some DNOs offer this for free; others charge a pre-application fee of £2,000–£5,000 for detailed feasibility. National Grid Electricity Distribution (NGED), Scottish Power Energy Networks (SPEN), UK Power Networks (UKPN), and Northern Powergrid all have different processes. Check the relevant DNO's ICPcross and connection portal for the current process and fees.
The outcome of Stage 1 is a rough cost range and an indication of whether the connection will require reinforcement of the local network — substation, transformers, or cable routes — beyond the site boundary. This is the first moment where operators discover whether they are looking at a six-figure cost or something substantially larger.
Stage 2: Formal Connection Application (8–16 weeks, £3,000–£15,000 design fee)
The formal application requires a site plan, single-line diagram of the proposed electrical installation, maximum import capacity required in kVA, load profile covering the daily and weekly demand pattern, and confirmation of metering requirements. The DNO uses these documents to design the connection and produce a Connection Offer.
The Connection Offer document is the central deliverable of the application process. It contains the offered connection voltage — LV or HV, typically 11kV for loads over 500 kW — the offered capacity, the connection cost that the operator pays the DNO, the required reinforcement works and who bears them, and the estimated connection date. That last item is the one that most frequently produces a sharp intake of breath.
The design fee is charged at this stage whether the operator accepts the offer or not. It covers the DNO's engineering time to produce the Connection Offer document. Refusing the offer does not recover the fee.
Stage 3: Acceptance, Civils, and Energisation (12–24 months from offer acceptance)
Once an operator accepts the Connection Offer, the DNO schedules the civils work — cable trenching, substation equipment installation, metering, and energisation. This stage takes 12–24 months in most UK regions, and longer where primary substation reinforcement is required. In areas where the primary network is under significant constraint, timelines beyond 24 months are not uncommon.
The civils work itself is separate from the operator's own electrical installation — the site-side distribution boards, earthing, and charger connection. Both programmes run in parallel but are not always coordinated. This is one of the most common causes of delay: the site-side installation completes on schedule, but the DNO has not yet energised the connection. The chargers are installed and tested. The vehicles are delivered. There is simply no power to run them.
What Does It Actually Cost?
The connection cost varies significantly by the capacity required and whether it involves reinforcement of the local network. The table below sets out typical ranges by depot capacity, based on UK DNO connection offers across the bus, coach, and HGV sectors in 2025–2026.
| Depot Capacity Required | Typical Connection Type | Typical DNO Cost | Typical Timeline |
|---|---|---|---|
| Up to 200 kW | LV reinforcement | £20,000–£80,000 | 6–12 months |
| 200–500 kW | LV or 11kV HV | £80,000–£200,000 | 12–18 months |
| 500 kW–1 MW | 11kV HV (new service) | £150,000–£350,000 | 18–24 months |
| 1 MW–3 MW | 33kV or HV primary | £300,000–£600,000+ | 24–36 months |
| 3 MW+ | Bespoke HV arrangement | £500,000+ | 36+ months |
These costs are connection-only. They exclude site-side electrical works, distribution boards, switchgear, cable runs from the DNO point of connection to the charger plant room, and any building modifications required to accommodate the new electrical infrastructure.
The Hidden Costs Nobody Budgets For
The DNO connection cost is the most visible number. It appears in the Connection Offer document, it is formally quoted, and it is the figure operators typically use when reporting project costs internally. But the items below regularly appear after the Connection Offer arrives — and collectively they can add 50–100% to the total infrastructure cost.
Site-side distribution (LV switchboard, earthing, cable runs): £30,000–£120,000. The DNO's responsibility ends at the point of connection — typically a meter cabinet or HV switchroom. From that point to the charger plant room, all costs fall to the operator. On older industrial sites, this route often involves significant civil work: breaking and reinstating hardstanding, routing around drainage, or navigating building fabric that was never designed for large cable routes.
Substation room construction: £25,000–£60,000. If the site is moving from a low-voltage supply to an 11kV HV connection, a DNO-compliant switchroom must be built on site to house the HV switchgear and the transformer that steps voltage down to LV for the local distribution. A modular prefabricated unit typically costs £25,000–£60,000 installed; in-building construction for bespoke arrangements will be higher.
Protection systems and metering: £15,000–£40,000. HV connections require automatic protection relays — devices that isolate the connection in fault conditions and are tested and approved by the DNO before energisation. Combined with CT metering equipment and AMR (automated meter reading) infrastructure, this is a specialist scope that most operators have not encountered in previous electrical projects.
Network reinforcement beyond the site boundary. This is the line item that most often triggers the £400,000+ total project cost. If the local LV or HV network does not have sufficient headroom for the new connection — because other loads in the area have consumed the available capacity — the DNO must reinforce it before it can offer a connection at the required capacity. That reinforcement cost falls to the operator. It can range from a modest substation upgrade to a full primary substation reinforcement programme, with costs that significantly exceed the connection cost itself.
Electrical consultant fees: £8,000–£25,000. Few fleet operators have the in-house expertise to manage a DNO application. The single-line diagram, the load profile documentation, the protection philosophy, the interface with the DNO's engineering team, and the coordination of the parallel site-side installation all require a consulting engineer. Most operators who attempt to manage this process without specialist support experience delays at Stage 2 due to incomplete or non-compliant application documentation.
The Timeline Reality
The stages above describe the process. What follows is what an 18-month timeline looks like when mapped to a real project plan — and where the gaps between stages create the delays that most operators do not anticipate at the outset.
- Months 1–2: Pre-application enquiry submitted. Site survey conducted by the consulting engineer. Load profile analysis completed against the fleet's charging schedule.
- Months 3–5: Formal connection application prepared and submitted to the DNO. Design fee paid. Application enters the DNO queue.
- Months 5–8: DNO produces the Connection Offer. The duration of this window varies significantly by DNO and by the complexity of the reinforcement assessment. During periods of high connection demand — which has been the norm across most UK DNO regions since 2023 — the queue adds weeks or months.
- Month 8: Operator reviews the Connection Offer. Internal approval obtained. Offer accepted and returned to the DNO with the acceptance fee.
- Months 9–12: DNO civils programme begins. The operator's site-side electrical installation also begins during this window — distribution boards, cable routes, switchroom construction if required.
- Months 13–18: DNO energisation. Protection systems tested and approved. Chargers commissioned. First vehicles charged.
The most common planning error is starting the DNO application after the charger specification is complete. The connection application should begin at the same time as vehicle procurement — 12–18 months before the vehicles are due for delivery. Projects that get this right rarely experience infrastructure delays. Projects that don't are the ones that end up with parked electric buses and no power to charge them.
How to Reduce the Grid Connection Cost
There are three approaches that fleet operators use to manage DNO cost and timeline — and in many cases, to avoid the largest costs entirely.
1. Storage Augmentation on the Existing Supply
Rather than upgrading the grid connection, operators install battery storage on the DC bus. The storage charges slowly from the existing supply during off-peak hours and discharges at high power when vehicles plug in. For many depots, this approach entirely eliminates the need for a DNO upgrade. The Neutron Power Hub (215 kWh usable capacity, 100 kW continuous output) and Power Plant (3,727 kWh, 1 MW output) are designed specifically for this application. See our article on BESS vs grid upgrade for fleet charging for a detailed comparison of when storage augmentation is the right route.
2. HV Direct — Connect Directly to 11kV
For high-power depots of 500 kW and above that do require a new connection, Neutron's HV Direct architecture integrates the 11kV switchgear, transformer, LV distribution board, and charger output into a single factory-assembled unit. This eliminates the specialist substation room construction entirely — the unit arrives on site pre-tested and ready to connect — and reduces the site-side installation cost and programme time by up to 35% compared to conventional site-built HV infrastructure.
3. Phased Installation
Rather than specifying the full peak load from day one, operators can apply for an initial connection — say 500 kW — and expand it later. The first phase gets vehicles charging; the grid upgrade programme continues in the background. This approach requires careful demand management in Phase 1 to avoid the connection being exceeded at peak times, which the Neutron Grid EMS handles automatically by sequencing charger output against live grid headroom and storage state of charge.
Get an accurate picture of your grid connection before you commit to a timeline.
Neutron's engineering team will assess your existing supply, your fleet's energy demand, and whether storage augmentation, HV Direct, or a phased DNO application is the right route for your depot — before any procurement decision is made.
Book a Site Assessment