What an Electrical Site Survey Is
An electrical site survey is a structured on-site assessment used to determine whether a location can safely and cost-effectively support new electrical loads — like EV chargers — and what upgrades, civil works, and compliance steps are required. It combines technical inspection, measurements, documentation review, and practical constraints (space, routes, access, operations).
Why Electrical Site Surveys Matter for EV Charging
A good survey prevents expensive surprises later. It helps you:
– Confirm available capacity and the real limiting constraints (breaker, transformer, feeder)
– Identify the correct earthing system (TT/TN) and protection strategy
– Plan cable routes, ducting, and bay layout with realistic civil scope
– Estimate costs and lead times, including DNO connection impacts
– Reduce commissioning failures and nuisance trips by catching risks early
– Build a complete design pack for permits, tendering, and installation
What a Survey Typically Covers
Supply and Capacity
– Incoming supply rating (phases, voltage, main fuse/breaker)
– Existing maximum demand (where data is available)
– Transformer/switchgear capacity and spare ways in DBs
– Voltage drop risk on long runs and expected continuous load limits
– Expansion potential (future chargers)
Earthing and Protection
– Earthing arrangement (TN-S, TN-C-S/PME, TT)
– Condition of bonding and earth bars
– RCD/RCBO strategy feasibility and selectivity considerations
– SPD presence/need and fault level assumptions
– Space for additional protection devices and metering
Cable Routes and Civil Works
– Practical cable paths from supply to charger locations
– Trenching feasibility, reinstatement constraints, and obstacles
– Need for duct banks, directional drilling, road crossings
– Depth/cover constraints and separation from other utilities
– Locations for pull pits/handholes (long runs)
Charger Locations and Layout
– Bay geometry (standard vs drive-through bays) and traffic flow
– Accessibility considerations (disabled bays, clear zones)
– Mounting surfaces and foundations (bollards, pedestals)
– Cable management and trip hazards
– Lighting, signage, and security
Communications and Control
– Connectivity options (Ethernet, cellular, Wi-Fi) and signal strength
– Space for routers/gateways and power supply for comms equipment
– Feasibility of dynamic load management (meter/CT installation points)
– Integration needs: CPMS, building loads, EMS/DER, fleet systems
Environmental and Operational Factors
– Water ingress risk, drainage, corrosion exposure
– Temperature extremes, ventilation constraints
– Operational windows and site access for works
– Safety management: pedestrian separation, emergency isolation requirements
Outputs You Should Expect
A solid site survey typically produces:
– Photos + annotated site plan with charger locations and cable routes
– Supply details and capacity conclusion (including constraints)
– Proposed electrical architecture (DB placement, feeder grouping, protection concept)
– Civil scope (trenching/ducting/pits) and reinstatement notes
– Connectivity plan and load management concept (if needed)
– Risk list + assumptions + next actions (permits, DNO application, detailed design)
Common Pitfalls
– Relying on “nameplate” supply ratings without checking real spare capacity
– Missing earthing details (TT vs TN) → wrong protection design
– Underestimating civil works (road crossings, utilities conflicts)
– Not checking comms in basements/metal structures → CPMS issues later
– No plan for expansion (no spare ducts, undersized DB/switchgear)
– Survey done without operational input (yard flow, shifts, parking behavior)
Related Terms for Internal Linking
– Electrical commissioning
– Electrical permits
– Distribution boards
– Ducting / duct banks
– Dynamic load management
– Earthing system
– DNO