DNO Applications for EV Chargers: How They Work (and How to Avoid Delays)
An independent walkthrough of ENA Form A, G99, supply upgrades and load management — and how to design a scheme your DNO will actually approve quickly.
A DNO application is the formal notification (or request for permission) to your Distribution Network Operator before connecting new EV chargers above certain thresholds. Get it right and it's a 10-week paperwork exercise. Get it wrong and you can lose 6–18 months and tens of thousands of pounds.
When you actually need to apply
- Single-phase chargers > 16A (3.6kW): ENA notification after install (Form A).
- Three-phase chargers, any size: ENA notification (Form A).
- Total site demand exceeding existing agreed capacity: formal G99 application, DNO approval required before works.
- New substation or reinforcement needed: ENA Connection Application + quote, can take 3–12 months.
The three documents you'll deal with
ENA Form A (notification)
Submitted after commissioning for small connections. Low friction — your installer usually handles it. Doesn't gate the project.
G99 application (approval)
Required when chargers or other generation/load triggers exceed the DNO's "fit and inform" thresholds. You submit a single-line diagram, protection settings and load profile. DNO has up to 65 working days to respond (often faster). Energisation cannot happen until approval is issued.
Connection offer (reinforcement)
If the local network can't take your new demand, the DNO issues a quote for reinforcement: bigger transformer, new feeder, sometimes a new substation. This is where the £50k–£500k bills and 12+ month timelines appear. Always get an indicative connection enquiry back before signing a lease or committing CapEx.
How to avoid DNO delays
- Design for available capacity first. Dynamic load management can keep you under the existing MIC and skip G99 entirely.
- Submit early. A G99 in week 1 of the project runs in parallel with civils design — not after.
- Send a clean pack. Single-line diagram, load schedule, protection settings, chargepoint datasheets. Missing documents reset the clock.
- Know your DNO. UKPN, SSEN, NGED, SP Energy Networks and ENW all have different forms, portals and turnaround patterns.
- Match charger specs to grid code. Off-the-shelf rapid chargers don't always meet G99 protection settings out of the box.
What a good DNO submission looks like
- Site plan with proposed charger locations and cable routes.
- Single-line electrical diagram showing the new EV demand at the LV board.
- Diversified vs absolute peak load calculation.
- Load management strategy (if used) with worst-case behaviour.
- Datasheets and G99 type-test certificates for each charger model.
When to pay for a formal feasibility study
For schemes above ~150kW additional demand, or any site near urban capacity hotspots (central London, Manchester, Birmingham, Bristol), a paid feasibility study with a DNO budget estimate is almost always worth £2,000–£5,000. It de-risks the business case before you sign leases or commit to a CPO contract.
We handle DNO liaison as an independent consultant — vendor-agnostic, and we'll happily review another contractor's G99 pack for a fixed fee. Start with the free feasibility calculator or email info@burtonengandinfra.com.