What percentage of carpark spaces need EV charging provisions under NCC 2025?

Class 2 buildings (apartments) must provide EV-ready infrastructure for 100% of carpark spaces. Class 5 and 6 buildings (offices, shops) must cover 10% of spaces. Class 3, 7b, 8, and 9 buildings (hotels, warehouses, factories, public buildings) must cover 20% of spaces. All sizing is based on a 7 kW / 32 A Type 2 charger.

Does NCC 2025 require installing EV chargers in new buildings?

No. NCC 2025 requires the electrical infrastructure to support future EV chargers, not the chargers themselves. This means dedicated distribution boards, conduit routes, and load management provisions must be installed during construction. The proposed NCC 2025 may move towards mandatory charger installation for some building classes.

What is the minimum energy delivery requirement for EV charging under NCC 2025?

Class 2 buildings must deliver a minimum of 12 kWh per space between 11 PM and 7 AM. Class 3 buildings (hotels) must deliver 48 kWh per space in the same window. Commercial buildings (Class 5-9) must deliver 12 kWh per space between 9 AM and 5 PM.

How much transformer capacity should I allocate for EV charging?

For a Class 2 apartment building with load management, allocate 15 to 25% of total transformer capacity for EV charging. The NCC minimum energy delivery of 12 kWh over 8 hours means each charger averages just 1.5 kW, so 150 spaces can be served from roughly 225 kW of allocated capacity rather than the full 1,050 kW connected load.

What type of RCD is required for EV charger circuits in Australia?

AS/NZS 3000 requires a Type B RCD for EV charger circuits to protect against DC fault currents. If the charger has built-in DC fault detection capability, a Type A RCD is acceptable. If the charger has a built-in Type B RCD, only an MCB is needed at the switchboard.

EV Charging Infrastructure in New Buildings

Section 1

What You Need to Know

NCC 2025 requires every new building with a carpark (Class 2, 3, 5, 6, 7b, 8, and 9) to include dedicated electrical distribution boards sized for future EV chargers. The code does not require you to install chargers today, but your electrical design must support them from day one. Get the distribution board sizing and conduit routes wrong now, and the retrofit cost will be 3 to 5 times higher than doing it upfront.

Section 2

The Rules

New carparks must have a dedicated distribution board for EV charging (DB-EV) on each storey of the carpark (NCC 2025, Table J9D4)
Class 2 buildings (apartments) must size DB-EV for 100% of carpark spaces at 7 kW / 32 A per space (NCC 2025, J9D4)
Class 5 and 6 buildings (offices, shops) must size DB-EV for 10% of spaces (NCC 2025, Table J9D4)
Class 3, 7b, 8, and 9 buildings (hotels, warehouses, factories, public buildings) must size DB-EV for 20% of spaces (NCC 2025, Table J9D4)
Each circuit must support a minimum energy delivery of 12 kWh per charge window (11 PM to 7 AM for residential, 9 AM to 5 PM for commercial) (NCC 2025, J9D4)
Class 3 buildings (hotels, motels) require 48 kWh per circuit between 11 PM and 7 AM (NCC 2025, J9D4)
A charging control system (load management) is mandatory to schedule charging based on total building demand (NCC 2025, J9D4)
Space for individual sub-circuit metering must be provided in each DB-EV (NCC 2025, J9D4)
Each EV charger circuit needs a dedicated 32 A circuit with a Type B RCD unless the charger has built-in DC fault detection (AS/NZS 3000:2018, Appendix P)
Standalone Class 7a carparks (public carparks) are exempt (NCC 2025, J9D4)

Section 3

What This Means in Practice

Take a 10-storey Class 2 apartment building with 150 carpark spaces across 3 basement levels. At 100% EV-ready, every space needs a 7 kW circuit allocation. That is 150 spaces × 7 kW = 1,050 kW of total connected load if every charger ran at full power at the same time.

No building can afford a 1,050 kW supply just for car charging. This is where load management earns its keep. The NCC requires only 12 kWh delivery per space overnight (11 PM to 7 AM = 8 hours). That means each charger needs an average output of just 1.5 kW during that window. With dynamic load management, you can serve all 150 spaces from roughly 225 kW of allocated transformer capacity (150 × 1.5 kW), not the full 1,050 kW.

For a Class 5 office building with 200 spaces, only 10% (20 spaces) need EV-ready circuits. At 7 kW each, that is 140 kW of connected load. With load management distributing 12 kWh across the 8-hour business day, average demand per charger drops to 1.5 kW. Total allocated capacity: about 30 kW. That is a small fraction of a typical office building's 500 to 800 kW maximum demand.

Your DB-EV should sit as close to the carpark as possible to keep cable runs short. Budget 1.5 to 2.5 m of clear wall space per DB-EV, and run conduit routes during the base build. A single 50 mm conduit from the DB-EV to a row of 6 spaces handles the cable capacity for Mode 3 charging.

Section 4

Key Design Decisions

1

Transformer Capacity Allocation

Decide early how much of the building's transformer capacity goes to EV charging. For a Class 2 building, 15 to 25% of total transformer capacity is a reasonable starting point when load management is in place. Undersize this now, and a transformer upgrade later costs $80,000 to $200,000 installed.

Trade-off: Allocating more capacity upfront increases the initial transformer cost by $10,000 to $30,000, but avoids a full replacement when EV uptake hits 50% or more of spaces.

2

Static vs Dynamic Load Management

Static load management splits a fixed power budget equally across all active chargers. Dynamic load management reads real-time building demand through a current transformer (CT) on the main switchboard and adjusts charger output second by second. The NCC requires a "charging control system" but does not specify which type.

Trade-off: Dynamic systems cost $3,000 to $8,000 more than static but deliver 30 to 50% more energy per charger by using spare building capacity during off-peak periods.

3

Metering Architecture

The NCC requires space for individual sub-circuit metering in each DB-EV. You can install meters now or leave provisions for future meters. For Class 2 buildings, each lot owner will want separate billing, so install meters from day one. For commercial buildings, a single meter on the DB-EV may suffice initially.

Trade-off: Installing individual meters at fit-out adds $200 to $400 per circuit. Retrofitting meters later costs $500 to $800 per circuit due to shutdown and re-wiring.

4

Conduit and Cable Route Planning

Run conduits from the DB-EV to each parking space (or group of spaces) during the base build. This is the cheapest time to install them. Cutting into a finished concrete slab later to run cables costs 5 to 10 times more than installing a conduit during construction.

Trade-off: Installing conduits to 100% of spaces in a Class 2 building adds $300 to $500 per space, but the alternative is core-drilling finished slabs at $2,000 to $4,000 per space.

Section 5

Who Needs to Know What

Section 6

References

National Construction Code 2022, Volume One, Part J9 — Energy monitoring and on-site distributed energy resources (J9D4: EV charging facilities; J9D3: energy monitoring)
AS/NZS 3000:2018 (Amendment 3, 2023), Australian/New Zealand Wiring Rules — Appendix P (EV charging installations)
AS/NZS 3001.2:2022, Electrical installations — Transportable structures and vehicles (EV supply equipment)
ABCB, NCC 2025 Guidance Material - Electric Vehicle Charging, DCCEEW
Electric Vehicle Council, Domestic EV Charging Related National and State-Based Regulations Guideline
NSW Climate and Energy Action, Making Your Commercial Building EV Ready

EV Charging Infrastructure in New Buildings

What You Need to Know

The Rules

What This Means in Practice

Key Design Decisions

Transformer Capacity Allocation

Static vs Dynamic Load Management

Metering Architecture

Conduit and Cable Route Planning

Who Needs to Know What

Need this engineered for your project?

References

Related design memos

EV Charging Infrastructure: What Building Services Engineers Need to Design

Maximum Demand Calculations for Commercial Buildings

Electrical Distribution Board Sizing and Layout