15 kW Off-Grid Solar Systems
Powering Large Homes and Productive Farms
When you need serious power for a large rural home, productive farm, or mixed-use property, a 15 kW off-grid solar system is often the perfect solution.
This size system delivers enough solar generation and battery storage to comfortably run a large homestead, multiple pumps, cold rooms, and even small machinery — with very minimal generator use.
At Stand-Alone Power Systems, we design, supply and install robust 15 kW stand-alone systems across Queensland, using only high-quality components that are proven to perform in hot, dusty rural conditions.
Who is a 15 kW Off-Grid System For?
A 15 kW solar + battery system is ideal for:
- Large family homes (4+ bedrooms, multiple air conditioners, multiple fridges/ freezers)
- Working farms with pump loads, irrigation systems, and high overnight demand
- Workshops and sheds running welders, compressors, and machinery
- Mixed-use rural properties where power reliability supports both home and business needs
If you are currently running a diesel generator for hours every day or facing tens of thousands in grid connection fees; a properly designed 15 kW off-grid system is a smart long-term investment.
Typical Daily Power Usage
A well-designed 15 kW system can comfortably deliver 50 – 65 kWh per day, depending on location, battery size, and season.
This level of generation ensures power security year-round, even with air-conditioning or heavier workshop use during busy seasons.
It will confidently run irrigation pumps, compressors, welders and other tools either during the day and at night if needed.
Components of a Typical 15 kW Off-Grid System
- 36 × 440 W Suntech Solar panels – 15.84 kW total capacity, backed by a 25-year performance warranty
- Clenergy cyclone-rated mounting system – suitable for Queensland rural wind conditions
- Selectronic SP PRO inverter/charger – Australia’s benchmark off-grid inverter, with generator integration, with a 5 year extended to 10 years if remotely connected to the internet.
- Victron SmartSolar 100 A MPPT charge controllers – three units, internet monitoring included
- 50 kWh usable Pytontech LiFePO₄ battery bank – modular design, expandable to 80 kWh
- Australian-made battery enclosures and switchgear – vermin-proof, dust-sealed, to AS/NZS standards
- Safety signs, cabling, and circuit protection – fully compliant with electrical standards
This combination is carefully sized not only for today’s load but with future growth in mind.
It allows for extra solar charge controllers, additional batteries, or even a larger inverter to be added later without needing to redesign the whole system.
Battery Storage – 24/7 Energy Security
Battery capacity is the key to making an off-grid system work seamlessly. This configuration includes a 50 kWh lithium iron phosphate battery bank; enough to power the home and farm overnight and keep pumps running through several cloudy days.
Advantages of LiFePO₄ batteries:
- High usable capacity: Up to 90 % depth of discharge
- Long lifespan: Thousands of cycles for 10+ years of use
- Low maintenance: No topping up or equalising needed
- Expandable design: Easily add more modules later
For properties with higher seasonal loads (e.g., irrigation during summer), we recommend sizing slightly above average demand, reducing generator run time.
Array Layout & MPPT Design
A key part of a reliable off-grid system is panel orientation and MPPT grouping.
For 15 kW arrays, we can:
- Split the array across two or three roof or ground-mount orientations (e.g. north-east + north-west) to spread generation across the day
- Use multiple 100 A Victron SmartSolar MPPT controllers to optimise efficiency and allow future panel expansion
- Size cable runs to minimise voltage drop, crucial for large arrays far from the battery shed
This ensures maximum solar harvest even on hazy or partly cloudy days.
Generator Backup (Integrated, Not Dependent)
Every 15 kW system we install includes automatic generator start capability. The generator only runs when battery levels drop below a set point (or manually on demand), saving.
- Fuel costs – typically reducing generator run time to only a few times a year.
- Wear and tear – less servicing and longer generator lifespan
- Noise – a quieter property
This hybrid design means you get the best of both worlds; solar first, generator only
Monitoring and Maintenance
We include remote monitoring with every system, allowing you and us to see:
- Solar generation by day and by MPPT
- Battery state of charge and health
- Load profile (day vs night usage)
- Generator runtime
Regular monitoring allows proactive maintenance and quick troubleshooting. We recommend:
Annual Inspection
Check panel cleanliness, cable integrity, and enclosure sealsFirmware Updates
Keep inverter and charger software currentBattery Health Check
Confirm modules are balanced and performing
With good maintenance, you can expect 15+ years of reliable service from the major system components.
Investment & Long-Term Savings
From the sample system shown:
- System cost: $61,410
- Available battery rebate: $16,948
- STC incentive: $4,978
- Net customer cost: $45,625
Over a 10–15 year lifespan, this investment is typically far cheaper than paying for a grid connection (often $50,000 – $80,000 for remote farms) or running a diesel generator every day.
Real-World Example: Warwick Property
In August 2025, we propose to install a 15 kW system on a mixed cattle and cropping property near Warwick, QLD.
The Challenge:
The customer is faced with a quote from the local electrical distributor at an estimated cost of $50,000. We anticipate that if the property is connected to the main grid, then the average cost of power for each year would be $5,000. Over 15 years, this would amount to $125,000. Even if the cost of replacing batteries is $10,000 after 10 years, it would make financial sense to install off-grid solar.
Our Solution:
• 15.84 kW solar array
• 50 kWh LiFePO4 battery bank
• Selectronic SP PRO inverter + generator auto-start
• Full monitoring for remote access, if required.
Results:
• Generator runtime to only a few times a year, during overcast weather.
• Annual diesel bill dropped by over 95 %
• Owners now have quiet, reliable, clean power 24/7
Why Choose Stand-Alone Power Systems
For nearly 20 years, we’ve specialised in designing off-grid systems that work — first time, long term. Our approach is simple:
• Proven Products
We only use components with excellent track records
• Custom Design
Every system matched to property’s load profile
• Flexible Layouts
Allowing for future expansion without major redesign
• Full Support
Warranty honoured, upgrades available, remote troubleshooting
Ready to Power Your Farm or Homestead?
If you’re ready to invest in reliable power and eliminate generator headaches, we can help you design a 15 kW off-grid solar system that meets your exact needs.
Contact us today to discuss your property, get a detailed load assessment, and receive a tailored system proposal.