Free Maximum Demand Calculator — AS/NZS 3000
Over 63A Per Phase? Let's Talk Supply Upgrades.
As Sydney Level 2 ASP electricians, we upgrade consumer mains, switchboards and supplies — from 63A single-phase right through to 400A three-phase — and we handle the Ausgrid, Endeavour or Essential Energy paperwork for you.
Ready to Confirm Your Maximum Demand?
Maximum Demand Calculator — AS/NZS 3000:2018, Table C1
How to Use the Maximum Demand Calculator
Step 1 — Pick your installation type. Choose 'House or individual unit' for a single home, or 'Block of living units' for strata and multi-unit common mains. Then select single-phase or three-phase supply — on three-phase you enter quantities per phase (Red / White / Blue).
Step 2 — Add your loads, one group at a time. Count lighting points and power points (a double power point counts as two), enter the cooking range in kilowatts, storage hot water, air conditioners (use the maximum input amps from the nameplate, not the cooling kilowatts), pool equipment and any EV charger. The calculator applies the Table C1 diversity rules — 50% for cooking, 75% for air conditioning, 100% for EV chargers — automatically.
Step 3 — Read the result. You'll see the demand on each phase, your maximum demand, and the next standard main switch size. Open 'Show the full working' for the line-by-line calculation, and use the print button to save a PDF for your records or your electrician.
A tip from the tools: if your result is over 63A per phase, or you're adding an EV charger, ducted air conditioning or a pool, your supply and consumer mains probably need attention. That work — anything between the street and your main switch — must be done by a Level 2 ASP electrician in NSW. We assess maximum demand on site, upgrade supplies from 63A to 400A, and lodge the distributor paperwork for you, so call us before you buy equipment.
Read the full step-by-step guide to calculating maximum demand →FAQs
Explore our frequently asked questions to learn more about the specialised services provided by our certified Level 2 Electricians.
Maximum demand is the highest current your installation is expected to draw at any one time, in amps per phase. It's not the total of everything switched on at once — AS/NZS 3000 applies diversity because loads don't all run together. It determines the size of your consumer mains, main switch and supply.
Table C1 in Appendix C groups your loads — lighting, power points, cooking, hot water, air conditioning, EV charging — and applies a fixed allowance or percentage to each group. Add the results per phase; the busiest phase is your maximum demand. Our calculator applies these rules automatically and shows the working line by line.
Connected load is the total nameplate rating of everything installed. Maximum demand is what realistically flows at peak, after diversity. A 9kW cooking range counts at only 50%, for example, because you'll rarely run every hotplate and the oven flat out at the same moment.
Yes — significantly. Table C1 counts an EV charger over 10A at 100% of its rating with no diversity, so a 7kW charger adds roughly 30A to one phase. That's why many homes adding a charger also need a supply or switchboard upgrade, or a load-management device. Our calculator has an EV load group so you can see the effect instantly.
When your maximum demand exceeds what a single-phase supply can deliver — typically 63–100A depending on your network — or when you run three-phase equipment like ducted air conditioning, lifts or workshop machinery. Spreading single-phase loads across three phases also lowers the demand on each.
Your consumer mains must carry your maximum demand and stay within voltage-drop limits under AS/NZS 3008. Once you have your demand figure from this page, run it through our cable size calculator — 16mm² and 25mm² copper are common for homes, with larger sizes for bigger demands and long runs.
Yes. Columns 3 to 5 of Table C1 use per-unit allowances that shrink as the number of units grows, because diversity increases across many households. Our calculator has a dedicated mode for blocks of living units — 2–5, 6–20 and 21+ units per phase — plus communal loads like lifts, pools and carpark lighting.
A licensed electrician assesses maximum demand, and any change to your supply, metering or consumer mains is Level 2 ASP work under the NSW Service and Installation Rules. High Demand Electrical is Level 2 accredited, so we can assess, upgrade and lodge the network paperwork in one job.
Your maximum demand is set by the busiest phase. If most loads sit on one phase, that phase drives the demand while the others sit idle. Spreading single-phase loads evenly across red, white and blue lowers the peak — the calculator warns you when your phases are noticeably out of balance.
No — it gives an estimate to AS/NZS 3000 Table C1 with the working shown. A licensed electrician still needs to confirm your loads, switchboard and available supply capacity on site before any upgrade. Print your result and we'll take it from there.
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If you’re looking for a reliable, experienced, and prompt electrician, look no further than High Demand Electrical. We cater to all your electrical needs, from routine maintenance to emergency repairs and complete system installations. Our skilled team is committed to providing professional service that ensures your electrical systems run smoothly. Whether it's a small task or a large project, give us a call today. Let us meet all your electrical demands with the quality and reliability you deserve.
