Power Logging for Maximum Demand: Can Your Building Handle EV Chargers or Extra Load?

Thinking about adding EV chargers to your strata block? Want to install a commercial kitchen, a new air-conditioning plant, or more solar in a Sydney office building? Wondering if the existing switchboard and consumer mains can actually handle it? Before you spend a dollar on hardware, there is one service that answers the question with data rather than guesswork: power logging.

What is power logging?

Power logging is the process of installing a professional-grade recording instrument — typically a Fluke power logger, a Dranetz, or equivalent device — at a key point in your electrical system. The logger measures voltage, current, power, harmonics, and power factor on every phase at short intervals, typically every 10 seconds to 10 minutes, for a period of 7 days.

Seven days is the sweet spot: it gives us a complete weekly cycle — weekday business-hour peaks, evening and overnight off-peak troughs, and full weekend patterns — so we see what the building really does across every usage mode, not just a random afternoon.

Why Sydney property owners are ordering power logging studies in 2026

Three trends are driving demand for power logging in Sydney right now:

1. EV charger rollouts. Residential strata buildings, commercial car parks, and fleet depots all want to add EV chargers — often multiple 7 kW, 11 kW, or 22 kW units per property. That's a significant new continuous load that wasn't in the original design.
2. Electrification. Replacing gas with induction cooking, heat pumps, hot water, and HVAC pushes electricity demand up sharply. Many commercial kitchens and apartment buildings are hitting the same switchboard capacity limits all at once.
3. Solar and batteries. New connection applications for solar above certain sizes, and all battery storage systems, often need real load data before Ausgrid or Endeavour Energy will approve the connection.

In each case, the question is the same: how much spare capacity does the building actually have? Power logging answers it.

Maximum demand: calculated vs measured

Every electrical design in Australia starts with a maximum demand calculation. Designers use AS/NZS 3000 Appendix C to add up the loads of every appliance, lighting circuit, and socket outlet, apply diversity factors (not every load runs simultaneously), and arrive at a theoretical maximum demand figure in amps or kVA.

This is perfectly adequate for new buildings where no historical data exists. But for existing buildings, Appendix C is often overly conservative. A strata building rated at 400 amps on paper might peak at only 220 amps in practice because not every unit runs the aircon, oven, and hot water simultaneously.

That gap between calculated and measured maximum demand is exactly where power logging creates value. A logged study shows:

• The real peak demand the building actually hits, in kW and amps, per phase.
• When peaks occur (weekday mornings, summer evenings, etc.).
• The troughs — after-hours and weekend off-peak windows when the system has lots of spare capacity (important for EV charging, which mostly happens overnight).
• How much spare capacity exists in the switchboard, mains, and upstream supply.
• Whether that spare capacity is enough to add EV chargers, solar, a battery, more cooling, or another specific load.

Typical findings in Sydney buildings

From our own logging studies across Sydney in 2025 and 2026, here's roughly what we see:

• Residential strata buildings (20–50 units): Measured peak demand is typically 50–70% of the Appendix C calculated figure. Many buildings have enough spare capacity for 4–8 shared 7kW EV chargers with load management — without upgrading the mains.
• Commercial office buildings: Peak demand is often dominated by HVAC on hot afternoons. Adding EV chargers that charge overnight (when HVAC is off) is usually viable without any upgrade.
• Retail/hospitality sites: Variable. Commercial kitchens and large retailers frequently use 80% or more of switchboard capacity during peak trading. Further load requires supply upgrades.
• Industrial sites: Highly variable. Heavy motor loads can mask significant spare capacity at other times of day.

The point is simple: you don't know until you measure. Many buildings that owners assume are "at capacity" actually have substantial headroom — and many that owners assume are fine actually have none.

How a power logging study actually works

Most power logging studies are a straightforward Level 2 electrician job. We attend site, install a Fluke (or equivalent) logger at your main switchboard, distribution board or sub-main, leave it running for 7 days, then come back, collect it, download the data, and produce a written report. No network involvement is needed for the logging itself.

The logger uses non-intrusive current transformers (CTs) clipped around your mains conductors and voltage probes connected at the switchboard — typically a 30-minute install on a planned outage. Your building keeps operating as normal during the 7-day study.

We deliberately run the study over a full week because load profiles look very different on a Tuesday afternoon versus a Saturday morning versus 2 AM on a Sunday. Capturing all of those — peaks, troughs, off-peak windows — is what lets us give you an accurate maximum-demand and spare-capacity number.

When you actually need a Level 1 + Level 3 ASP

Here's where it matters: power logging itself doesn't require Level 1 or Level 3 ASP accreditation. But the follow-up work often does — specifically when the logged data shows you need significantly more capacity than your existing supply can deliver.

If you want to add a substantial new load — typically more than about 100 amps of additional capacity — and Ausgrid or Endeavour Energy doesn't have the spare capacity in their existing network to give you, the network has to upgrade their infrastructure. That can mean a new transformer, an upgraded substation, new HV cabling, or in some cases a new pillar or pole-top transformer to feed your property.

That network-side work is exactly where ASP accreditations come in:

• Level 3 ASP designs the network upgrade — the transformer, the HV/LV layout, the protection scheme, the connection point.
• Level 1 ASP physically installs the upgraded network assets — transformer, HV cable, switchgear, substation works.

So the typical sequence for a major capacity upgrade is: (1) we run the 7-day power logging study to confirm what additional capacity you actually need, (2) if a network upgrade is required, our Level 3 ASP designs it, and (3) our Level 1 ASP delivers the install. For loads under that ~100 amp threshold, you usually don't get to that step at all — the existing supply already has enough headroom.

How much spare capacity do I need for EV chargers?

A rough guide for typical Sydney installations:

• Single 7 kW (32 A) home EV charger: 32 A per phase on single-phase, or ~11 A per phase balanced on three-phase.
• Single 22 kW (32 A three-phase) charger: 32 A per phase on three-phase.
• Shared 8-bay charger system with load management: typically 30–60 A total shared budget, intelligently allocated between bays.

With load management, even modest amounts of spare capacity can support multiple EV chargers — especially because EV charging mostly happens overnight, exactly when the logged data usually shows the biggest spare-capacity windows.

What the data can't tell you (and what it can save you)

Power logging tells you what the building has been doing, not what it will do in the future. If you're about to renovate, replace the HVAC, or change tenants, the measured data needs engineering judgement applied to project forward.

But the data absolutely can save you from the two biggest mistakes on capacity planning:

• Over-upgrading. Spending tens of thousands on a network upgrade you didn't actually need because the theoretical Appendix C number said you were "at capacity" when real peak was 60%.
• Under-upgrading. Adding a load without measuring first, causing nuisance trips, blown main fuses, or a network defect notice.

A 7-day logging study costs a fraction of an unnecessary upgrade. In most cases it pays for itself many times over in either saved upgrade work or de-risked installation of new loads.

When should you commission a power logging study?

Book a study if any of the following apply:

• You're planning to add EV chargers to a strata, office, commercial car park, or fleet site.
• You're adding solar, a battery system, or three-phase power.
• You're replacing gas with electric HVAC or hot water at scale.
• You're being told by an installer that you "need a network upgrade" — a logging study verifies whether that's actually true.
• You're having nuisance tripping or voltage complaints and need data to diagnose.
• You're doing due diligence on a property purchase or strata scheme takeover.

How long does a study take?

Typical timeline from call to report:

1. Day 1–3: Site visit, scope the study, issue written quote.
2. Day 3–7: Logger installed on a brief planned outage (typically 30 minutes offline).
3. Days 7–14: Logger runs in the background for 7 days — one full weekly cycle capturing weekday peaks, off-peak troughs and weekend patterns.
4. Day 14–21: Logger removed, data downloaded and analysed, written report delivered.

Two to three weeks from first call to report in hand — then you have the evidence you need to plan an upgrade, approve an EV rollout, or confirm you're fine as is.

HDE runs power logging studies across Sydney

We install and analyse 7-day power logging studies as a standard Level 2 service — no Level 1/3 ASP involvement is required for most jobs. If the data shows you need more capacity than the network can give you, we also hold Level 3 ASP design and Level 1 ASP installation accreditation, so we can take you all the way through to a substation or transformer upgrade if it ever comes to that.

If you're considering EV chargers, solar, batteries or any significant new load and want to know whether your existing infrastructure can handle it — get in touch for a power logging quote. We'll walk through your situation on the phone and quote a fixed-price 7-day study.

Better data. Less guesswork. Smaller surprises.