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

> EV charging in office or factory parking is an electrical supply project before it is a charger purchase. The number and type of chargers, AC for long stays or DC for quick top-ups, must fit the spare capacity of the existing supply and its sanctioned load, a metering arrangement agreed with the DISCOM, practical cable routes and the fire strategy for the parking area.

## 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

| Factor | AC charging | DC charging |
| --- | --- | --- |
| Where AC is converted to DC | In the vehicle's onboard charger | In the charging unit itself |
| Typical use | Long stays: staff parking, overnight fleet parking | Short stays: fleet vehicles between shifts, visitors |
| Power per point | Lower; ratings vary by charger and vehicle | Higher; ratings vary by charger |
| Supply needed | Single or three phase from the LV distribution | Three phase, usually a larger dedicated feeder |
| Effect on supply capacity | Smaller per point, but adds up across many bays | Large per point; can decide the transformer question |
| Equipment size | Wall-mounted or small pedestal | Larger cabinet needing space, ventilation and clearances |
| Relative installed cost | Lower | Higher |

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](/glossary/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](/services/mep/electrical-works-ht-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](/services/mep/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](/glossary/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.

## Frequently asked questions

### Should an office install AC or DC chargers?

It depends on how long vehicles stay. Staff cars parked for a working day can usually charge adequately on AC chargers, which draw less power per point and cost less to install. DC chargers suit vehicles that need a quick top-up, such as fleet vehicles between shifts or visitors. Many sites use mostly AC with a small number of DC points.

### Can EV chargers run on the building's existing electricity connection?

Sometimes. It depends on the spare capacity of the transformer, the main LT panel and the sanctioned load, measured against the building's actual maximum demand through the year. An electrical engineer should assess it from metered data. If capacity is short, load management, a load enhancement or a separate connection are the usual options.

### Do EV chargers need a separate meter?

Not always, but metering should be decided early. Chargers can be sub-metered on the building's connection to allocate cost to tenants, departments or users, or some DISCOMs offer a separate connection for EV charging under a specific tariff. Which options exist depends on the state's DISCOM and tariff order, so confirm with them before designing.

### Is EV charging allowed in a basement car park?

There is no single answer that fits every building. It depends on the building's fire strategy, the basement's ventilation and smoke control, sprinkler protection, firefighting access and the authority's view. NBC 2016 Part 4 is the fire and life safety framework, and the CEA regulations include fire-prevention provisions for charging stations. The fire consultant and the authority having jurisdiction decide.

### What is load management for EV chargers?

A control system that shares a fixed amount of available power between charging points, reducing each charger's output when many cars are connected or when the building's own load is high. It allows more charging points on a limited supply, at the cost of slower charging at peak times. It needs chargers and controls that support it, chosen at the start.

### Should we install chargers now or only prepare for them?

Many sites install a first set of chargers and prepare more bays for later, with containment, cable routes and panel capacity allowed now. Laying conduit while the car park is being built or resurfaced costs far less than cutting through finished floors and ceilings later. How many bays to prepare is a business decision based on expected EV uptake.

## Sources

- [CEA (Measures relating to Safety and Electric Supply) Regulations, 2023](https://cea.nic.in/regulations/?lang=en) — Safety provisions for electric vehicle charging stations
- [IS 17017 (Part 1)](https://standards.bis.gov.in/website/published-standards/department-wise) — Electric vehicle conductive charging system - general requirements
- [IEC 61851-1](https://webstore.iec.ch/en/) — Electric vehicle conductive charging system - general requirements
- [IS 732](https://standards.bis.gov.in/website/published-standards/department-wise) — Code of practice for electrical wiring installations
- [NBC 2016, Part 4](https://www.bis.gov.in/standards/national-building-code/) — Fire and life safety

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Source: https://hagerstone.com/blog/ev-charging-in-office-and-factory-parking