EV Charging in Office and Factory Parking: What to Plan First

The charger is the cheap part of the decision

When a company decides to offer EV charging, the conversation usually starts with the charger: which brand, how many, what speed. That is the wrong place to start, and it is the source of the commonest mistake, which is to buy chargers and connect them to the nearest distribution board.

An EV charger is a large, continuous electrical load. A group of them can add a significant share to the building's demand, for hours at a time, often at the same time of day as everything else. Whether a site can support that depends on the spare capacity of its supply: the transformer, the main LT panel, the cables, and the sanctioned load agreed with the distribution company.

Getting it wrong is expensive in ways that do not appear on the charger quote: penalties for exceeding the sanctioned load or contract demand, nuisance tripping when chargers and air conditioning peak together, a load enhancement application that holds up commissioning, and cables pulled through a finished basement because no route was planned.

AC or DC: match the charger to how long vehicles stay

For most offices, where cars stay for the working day, AC charging matches the need. Factories often have a mix: staff parking on AC, and DC for company vehicles or electric material-handling and logistics fleets that must turn around quickly. Conductive charging systems are covered by IS 17017 (Part 1) in India and by IEC 61851-1 internationally.

Load on the existing supply

The engineering question is how much power is genuinely spare, and when.

• Start from metered data. The building's maximum demand over a full year, from bills and meter records, shows the real headroom against the sanctioned load. Connected load on drawings is not the same thing; the difference is explained under sanctioned load.
• Check the whole chain. Transformer, main panel, spare outgoing ways and the cable to the parking area each have their own limit.
• Consider load management. Chargers that share a set power limit between them allow more charging points on a limited supply, at the cost of slower charging at peak.
• Decide on standby power. Whether chargers run on DG during outages is a deliberate decision; usually they do not, and the DG and changeover arrangements must reflect it.
• Look at power quality. Chargers are power-electronic loads. Their effect on harmonics and power factor should be assessed by the electrical engineer.

If spare capacity is short, the options are load management, a load enhancement with the DISCOM, or a separate connection. Each has a different timeline, and the application process sits outside the site programme, so it belongs on the critical path from the start. How the main supply is arranged is covered under electrical works, HT and LT.

Metering and the DISCOM

Metering decides who pays for charging and how the arrangement is approved.

• Sub-metering on the building's connection. Chargers are metered separately within the building, so energy can be allocated to tenants, departments or users. In a multi-tenant building, whether this is the landlord's system or the tenant's is a lease question to settle first.
• A separate connection for EV charging. Some DISCOMs offer a dedicated connection or tariff category for EV charging. Whether it is available, and on what terms, is set by the state's DISCOM and electricity regulator.

The Ministry of Power issues national guidelines for the installation and operation of EV charging infrastructure, most recently in 2024, covering public and semi-public places such as office buildings as well as private parking. How they are applied to a particular site is a matter for the DISCOM and the state's rules. Metering and monitoring systems are covered under energy metering and monitoring.

Cable routes and the parking area

The route from the panel to the parking bays is often longer and more congested than expected.

• Basements. Ceilings are already crowded with ventilation ducts, sprinkler pipes and drainage. New cable routes must be coordinated, and penetrations through fire compartments must be sealed.
• Distance and grouping. Long runs and cables grouped on one tray need larger sizes. Undersized grouped cables overheat without warning, as explained under cable derating.
• Physical protection. Chargers and cables need protection from vehicle impact, such as wheel stops and bollards.
• Outdoor and factory yards. Weather and dust protection should match the location, and long yard runs may need trenching across roads used by heavy vehicles.
• Earthing and protection. The CEA (Measures relating to Safety and Electric Supply) Regulations, 2023 include safety provisions for electric vehicle charging stations, including earth protection, fire prevention, testing and inspection. Wiring practice is set out in IS 732.

Basement fire: a framework, not a verdict

Fires involving vehicle batteries can behave differently from conventional vehicle fires: they can be hard to extinguish and can reignite. That has made charging in enclosed and basement car parks a question fire consultants now consider specifically. The questions they typically examine include:

• Where chargers are placed relative to ramps, exits and escape routes, and whether some or all can be located at grade.
• How the basement's smoke ventilation and sprinkler protection relate to the charging bays.
• Whether there is an emergency isolation for the chargers that firefighters can reach.
• How firefighting access works for the charging area.

Fire and life safety provisions sit in NBC 2016, Part 4, and the CEA regulations include fire-prevention requirements for charging stations. What is acceptable in a particular building is decided by the fire consultant and the authority having jurisdiction, not by the charger supplier.

Common mistakes

• Buying chargers before checking supply capacity. The chargers arrive; the power does not.
• Using connected load instead of metered demand. The headroom is either overstated or understated.
• No metering plan. Nobody can allocate the cost, so charging becomes free by default.
• Installing DC where AC would do. Higher cost and a bigger supply demand for cars that stay all day.
• No spare containment for future bays. Every expansion means cutting through finished floors and ceilings.
• Leaving the fire consultant out. The basement plan is changed after the equipment is bought.

What to ask before installing EV charging

• What is our actual maximum demand, and how much headroom remains against the sanctioned load?
• How many charging points now, and how many prepared for later?
• AC, DC or a mix, based on how long vehicles stay?
• Will load management be used, and do the chargers support it?
• Sub-metering or a separate connection, and what does the DISCOM offer?
• Where do the cables run, and what do they cross?
• Has the fire consultant reviewed charger locations in the car park?

Standards referenced

Safety provisions for electric vehicle charging stations in the CEA (Measures relating to Safety and Electric Supply) Regulations, 2023; conductive charging systems in IS 17017 (Part 1) and IEC 61851-1; wiring practice in IS 732; fire and life safety in NBC 2016, Part 4. Supply capacity, connection and metering arrangements are decided with the DISCOM, and the electrical design, charger locations and fire measures for a specific site must be established by the project's electrical engineer, fire consultant and the authority having jurisdiction.