How Much Power Does My Building Need for EV Chargers? A Strata Guide

More residents are buying electric vehicles, and sooner or later someone asks the committee: “Can we put chargers in the car park?” The honest answer depends on one thing most buildings have never measured – how much spare electrical capacity the building actually has. This guide explains how body corporates and strata managers in Brisbane and South East Queensland can work that out, what the options are, and when a switchboard or supply upgrade is needed.

Quick summary: measure the building’s real peak demand with data logging → compare it with what the supply and main switchboard can carry → choose chargers and load management to suit the spare capacity → upgrade the switchboard or supply only if the numbers say you need to.

How much power does an EV charger use?

Home and car park chargers come in a few common sizes:

• 7 kW single phase – about 32 amps on one phase. The most common choice for apartment and townhouse car parks; adds roughly 40–50 km of range per hour.
• 11 kW three phase – about 16 amps on each of three phases.
• 22 kW three phase – about 32 amps on each phase. Usually only worth it for shared or visitor bays, and only if the car can accept it.

One charger is rarely a problem. The issue is what happens when ten or twenty residents plug in at 6 pm – at the same time the building’s air conditioning, lifts, pool pumps and cooking load are peaking.

Step 1: Measure your building’s real peak demand

The only reliable way to know your spare capacity is to measure it. We install an energy data logger on the main switchboard, usually for one to four weeks, and record the current on each phase around the clock. That shows the true peak demand, when it happens, and whether one phase is carrying more than the others.

A desktop maximum-demand calculation is a useful starting point, but it is deliberately conservative and often says a building has no capacity when the measured load leaves plenty of room. Data logging gives the committee real numbers to make a decision with. You can see how this works in practice in our apartment block power assessment and our article on data logging and power capacity.

Step 2: Work out your spare capacity

Spare capacity is the difference between what your supply and main switchboard are rated to carry and the highest load the data logger recorded, less a safety margin. In simple terms:

Spare capacity per phase = supply rating – measured peak demand – safety margin

For example (illustrative figures only): a building with a 200 amp three phase supply that peaks at 140 amps on its busiest phase has around 60 amps of headroom on that phase before any margin. That could run one 7 kW charger at full power – or, with load management, share that capacity across many more chargers.

Step 3: Use load management before you upgrade

Load management (also called dynamic load balancing) monitors the building’s total demand and adjusts charging speed in real time so the supply limit is never exceeded. When the building is quiet overnight, cars charge at full speed; at the evening peak, they slow down. Because most cars are parked for 10 hours or more, residents rarely notice.

For many strata buildings, load management is the difference between needing a major supply upgrade and installing chargers on the existing supply. It also makes the system easier to expand as more residents buy EVs.

Step 4: Decide whether you need a switchboard or supply upgrade

You will probably need an upgrade if the data logging shows little or no headroom, if the main switchboard has no physical room for new circuits or a dedicated EV distribution board, or if the committee wants to future-proof for every car bay. Options include:

• a new EV distribution board fed from the main switchboard
• a main switchboard upgrade to add capacity and space
• a power capacity upgrade, including new consumer mains and an Energex supply application
• three phase upgrades for smaller complexes still on single phase supply

Any change to the supply needs Energex approval, and metering changes involve your energy retailer. We handle those applications as part of the job.

Step 5: Plan billing, approvals and rollout

• Billing: chargers can be connected to each lot’s own meter, or to common property with sub-metering or app-based billing so residents pay for what they use.
• Approvals: work on common property normally needs body corporate approval. Your strata manager can advise whether the committee can approve it or whether it needs to go to a general meeting.
• Staged rollout: many buildings install the backbone (capacity, distribution board and load management) once, then add individual chargers as residents request them.

For the wider switchboard process, see our body corporate switchboard upgrade guide.

Frequently asked questions

How many EV chargers can our building support?

It depends on your measured spare capacity and whether you use load management. Without load management, each 7 kW charger needs around 32 amps of headroom. With load management, the same capacity can often be shared across many more chargers.

How long does data logging take?

We usually log for one to four weeks so the results capture normal weekday and weekend use. You get a written report with the peak demand on each phase and our recommendation.

Do we need three phase power for EV chargers?

No. Most apartment car parks use 7 kW single phase chargers. Three phase supply helps balance the load across a large building and is needed for 11 kW and 22 kW chargers, but it isn’t required for basic resident charging.

Can you install the chargers as well?

Yes. We assess the capacity, upgrade the switchboard if needed, and install and commission the chargers. See our EV charger installations page.