Off-grid power for the shed, the bore and the back paddock.
No mains out here. Wattonomy sizes a stand-alone power system to your loads and your worst-case month, picks 24V or 48V to cut copper, and specs the wiring and battery install to AS/NZS.
Wire & fuse sizes follow AS/NZS 5139 — each conductor carries its fuse and stays under a 3% voltage drop.
Built to AS/NZS standards
Gauge · fuse · volt-drop sized
Every spec sourced
Out here, running out means a long drive for fuel.
Size for the average and a cloudy week leaves you dark; oversize blindly and you have spent thousands on panels you did not need. Wattonomy sizes to your days of autonomy and worst-case sun, and keeps the battery install within AS/NZS 5139 — out of habitable rooms, clear of exits and vents.
How an off-grid shed is sized
Stand-alone power lives or dies on autonomy and an honest worst-case month.
Days of autonomy
3-5 days of backup for cloudy stretches — the biggest driver of battery size.
Worst-case sun
Sized to your region’s low-production month, not the summer best case.
24V or 48V
Higher voltage for shed loads means thinner cable and less loss — we pick and size it.
Battery install
Location and clearances per AS/NZS 5139; wiring and protection per AS/NZS 3000 / 3008.
What you walk away with — free
A bank + array sized to your worst-case month
A wiring diagram with cable and protection sizing
Battery-location guidance per AS/NZS 5139
A vendor-neutral parts list
Building it for real? Unlock the build binder.
Free gets you a safe, correctly-sized design. The build binder gets you the documents to build it right — and prove it's right.
Printable wiring diagram, yours to keep & tape inside the shed
Full parts list, every line sourced
The volt-drop & fusing calculation trail — the "why" behind every spec
The build binder is a one-time unlock — no subscription, no auto-renew.
Questions
Will it size for winter?
Yes — sizing is driven by your days of autonomy and your region’s low-production month, so it holds through cloudy stretches.
Is it to AS/NZS?
The stand-alone design follows the AS/NZS 4509 approach, cable to AS/NZS 3008, and flags AS/NZS 5139 battery-location rules. The 240V side needs a licensed electrician.
12V, 24V or 48V?
For shed/station loads it generally moves to 24V or 48V to cut losses and copper, and sizes everything for that voltage.
Do I need an account?
No — free, no email. Accounts only for saving builds or the build binder.
The standards we build to
Plain version: these are the recognized rulebooks your design is sized against, so the numbers hold up to a surveyor, an inspector or an insurer.
AS/NZS 4509The Australian standard for stand-alone (off-grid) power systems.
AS/NZS 5139The Australian standard for battery-system installation, location and clearances.
AS/NZS 3000The Australian/NZ Wiring Rules for the 230 V side.
Wattonomy applies these standards in its calculations. It is not certified, sponsored or endorsed by ABYC, ISO, NFPA or Victron — it sizes your design to meet what they require, and shows the working.
Sized and checked to AS/NZS 3008. Last reviewed June 2026 — see the full methodology for the exact rules behind every number and how each design is validated.
Built by anABYC Certified Master Technician