Size an off-grid system to your worst weather, not your average week. The system must carry the property through the longest cloudy run you expect, then recharge in the sun.
The sizing comes from four steps: a load audit, the days of backup, the battery, and the panels for the weakest solar month. Our off-grid solar systems page explains the options in more detail.
Key Points
Off-grid sizing starts with a load audit of every appliance and its daily hours of use.
The number of backup days you choose drives the size of the battery.
Battery size comes from daily energy, days of backup and the usable share of the battery's capacity.
Panels are sized for the weakest solar month, not the summer peak.
Steven Hord's price for an off-grid system is $60,000 to $120,000, after the rebate.
We have not yet written up an off-grid job, so the method is the same as our grid-connected hybrid work.
Start with a load audit
List every appliance, its power draw and its daily hours of use. Include summer cooling, pumps, EV charging and any workshop equipment.
The total daily energy is your starting figure. Mark which loads must always run and which can wait.
Choose the days of backup
Decide how many days the battery must carry the property with little sun before a generator starts. More days means a larger battery.
A generator can cover the longest cloudy spells, so the battery does not have to be sized for the rarest storm.
Work out the battery size
Multiply daily energy by the days of backup. Then divide by the usable share of the battery's capacity, as stated on the manufacturer's data sheet. Use the usable figure, not the rated one.
A worked example
This example uses made-up numbers to show the method. It is not a sizing for any property.
A property uses 20 kWh a day, and the owner chooses 3 days of backup. The battery must hold 60 kWh of usable energy. If the battery's data sheet says 90% of its rated capacity is usable, the rated size must be about 67 kWh.
Size the panels for the weakest month
Divide daily energy by the peak sun hours in your weakest solar month, then allow for system losses. Size to that month, not the summer peak.
That stops the battery running low in winter. Sizing to the winter month costs more panels, but it keeps the property running through the dark months.
Plan the generator
A generator gives an off-grid system a fallback. It can recharge the battery and carry the load through a long wet spell. The generator must also be sized to carry the loads that run when the battery is low.
Ask for the generator's auto-start controls and servicing as separate line items. Fuel and servicing are ongoing costs, so put them in your budget.
Get the connection quote
Some rural properties can connect to the grid. Ask your network distributor, Energex or Ergon Energy, for an itemised connection quote. Compare it with the off-grid path over the same period.
Do not assume a grid connection is the cheaper option until you have both written quotes.
What does it cost?
An off-grid system costs $60,000 to $120,000, after the rebate. The price depends on the battery storage you need for cloudy weather, the generator, single, dual or three phase power, roof type, storeys, site access, and whether we trench or run overhead mains.
Prices are current as at October 2026. We give a written quote before any work begins.
Frequently Asked Questions
What size off-grid system does a rural property need?
It depends on the daily energy use, the days of backup you choose, and the weakest solar month. Start with a load audit to find your daily energy use.
How many days of backup should I choose?
That depends on how long the property must run with little sun before a generator starts. More days means a larger battery.
Do I need a generator with off-grid solar?
Many off-grid properties do. A generator recharges the battery and carries the load through the longest wet spells.
How much does an off-grid system cost?
Steven Hord's price is $60,000 to $120,000, after the rebate. The price depends on the storage, the generator, the phase, the roof, the site access and the trenching.
Ready for an off-grid site assessment?
Send us your property address and power bills, and we will start the load audit with you. Get a quote at /get-a-quote, or call us on 1300 153 011.
