NZ Maximum Demand Calculator — AS/NZS 3000
Maximum demand is the largest current an installation actually
draws at any one moment. It is almost never the simple arithmetic
sum of every connected load — diversity reduces the figure,
because not every appliance runs at full rated current at the same
time. WireWrite's NZ maximum-demand calculator applies the diversity
assessment method in AS/NZS 3000 Appendix C and recommends a main
switch and consumer-mains size from the result.
Why diversity matters
A typical NZ home might have a 9 kW oven, a 3 kW hot-water
cylinder, 12 power outlets, lighting, and a 7 kW EV charger. The
arithmetic sum of those rated loads is well over the supply
capacity. In practice the oven cycles, the cylinder element is on
a controlled load, lighting is at a fraction of rated, and the EV
charges overnight. Diversity factors capture that reality.
The two assessment methods
AS/NZS 3000 Appendix C describes two methods electricians can use:
- Assessment by calculation — applies
per-load-group diversity allowances from Appendix C tables for
domestic, multi-dwelling, and commercial installations. This is
the method the calculator implements.
- Assessment by measurement — a recording
ammeter is fitted to an existing installation of similar usage for
at least seven consecutive days and the maximum recorded current
is taken as the demand. Used only when an equivalent installation
is available.
Why "load schedule" is the wrong shortcut
Adding up every connected load in a switchboard schedule (the
protective-device "load" column) and treating that as maximum demand
will always oversize the consumer mains. AS/NZS 3000 explicitly
requires the diversity assessment for installations above
single-circuit final sub-circuits. The calculator lets you enter
each load group and applies the published allowances per appliance
type.
What the calculator outputs
You'll get the assessed maximum demand in amperes per phase, the
recommended main-switch and consumer-mains size from standard NZ
ranges, and a phase-balance suggestion if the installation is
three-phase. The result is suitable as the calculation reference on
your design records and certificates.
Calculate maximum demand
for your installation →
Digital electrical CoC certificates for NZ electricians. Download EWRB CoC templates and PDFs. Create Certificate of Compliance and Electrical Safety Certificates on-site. From $6/month.
Certificate of Compliance (CoC) Download & Examples
- CoC certificate PDF download - Generate and download professional CoC certificates instantly
- CoC electrical certificate examples - View sample certificates and templates
- Electrical certificate of compliance generator - Create EWRB-compliant certificates online
- EWRB CoV certificates - Certificate of Verification (CoV) support
- Digital signatures and professional PDF formatting
- Mobile-first design - create certificates on-site from any device
Electrical Safety Certificate NZ Features
- EWRB compliant digital certificates (CoC, ESC, RoI, CoV)
- AS/NZS 3000 compliant electrical certificates
- 30-day free trial - no credit card required
- Install as a mobile app (PWA) on any device
- Team collaboration for electrical contractors
- Two-factor authentication for account security
Free Electrical Calculators
- Voltage Drop Calculator - AS/NZS 3008.1 compliant
- Maximum Demand Calculator - AS/NZS 3000 Section 2
- Conductor Sizing Calculator - Cable sizing calculations
For Electrical Contractors
WireWrite Company Edition allows electrical contractors to manage team certificates, share client databases, and maintain compliance across all employees. Starting from NZD $40/month for up to 10 employees.
How to Download CoC Certificate Examples
Sign up at WireWrite to access our library of CoC certificate examples and templates. Start your 30-day free trial and create your first electrical safety certificate in minutes with our step-by-step wizard.
Start creating professional electrical certificates today: Visit wirewrite.co.nz or try our free demo