How Does an Off-Grid Solar System Work?
An off-grid solar system — also called a Stand-Alone Power System (SAPS) — generates, stores, and delivers electricity entirely independently of the Western Power network. Once installed, your property runs on its own power supply, with no ongoing reliance on the grid and no electricity bills from Synergy.
Here’s how the key components work together, and what you need to know before investing in one.
The Core Components
1. Solar Panels (Photovoltaic Modules)
Solar panels convert sunlight into direct current (DC) electricity through the photovoltaic effect. The amount of power generated depends on the number and efficiency of the panels, the available sunlight hours, panel orientation and tilt, and shading from trees or structures.
In Western Australia, the solar resource is exceptional — Perth receives an average of around 8 peak sun hours per day in summer and 4–5 in winter, making WA one of the best locations in the world for solar generation. Remote areas such as the Goldfields, Pilbara, and Kimberley receive even higher solar irradiance.
Modern panels from brands such as LONGi Solar are typically rated at 20–23% efficiency and carry 25-year performance warranties guaranteeing output above 80–85% of rated power after that period.
2. Charge Controller
The charge controller sits between the solar panels and the battery bank. Its job is to regulate the voltage and current flowing into the batteries to prevent overcharging and protect battery health.
Modern off-grid systems use MPPT (Maximum Power Point Tracking) charge controllers, which continuously optimise the power drawn from the solar array to maximise charging efficiency — typically achieving 93–98% efficiency compared to older PWM technology.
In many contemporary systems, particularly those using hybrid inverters from brands like Sigenergy or Victron Energy, the MPPT charge controller function is integrated directly into the inverter unit rather than being a separate component.
3. Battery Bank
The battery bank stores the DC electricity generated by solar panels for use when the sun isn’t shining — at night, during cloudy periods, or during high-demand times.
Lithium Iron Phosphate (LiFePO4)
LiFePO4 is the current standard for off-grid residential and commercial systems in Australia. Key advantages include:
- Cycle life of 3,000–6,000 cycles — typically 10–15 years under daily use
- High depth of discharge — 80–100% of capacity is usable without damaging the cells
- Excellent thermal stability and safety compared to other lithium chemistries
- Built-in Battery Management System (BMS) that protects against overcharge, over-discharge, and temperature extremes
Battery brands installed by OffGrid WA include Sigenergy, Pylontech, Power Plus Energy, and MPS Battery.
Lead-Acid Batteries
Lead-acid batteries (including AGM and gel variants) are an older technology still used in some applications. They typically last 5–10 years, offer a lower recommended depth of discharge (50%), require more maintenance, and are heavier and bulkier for equivalent storage capacity. They are increasingly being replaced by lithium technology in new installations.
Battery capacity is measured in kilowatt-hours (kWh). A typical WA home uses 15–25 kWh per day, so off-grid systems for residential use commonly include 20–40+ kWh of battery storage to provide multiple days of autonomy during poor weather.
4. Inverter/Charger
The inverter converts the DC electricity stored in the batteries into 240V AC electricity — the standard voltage used by appliances, lighting, and other loads throughout your home or business.
In modern off-grid systems, the inverter is typically a combined inverter/charger unit that also manages battery charging from the solar array and, if present, a backup generator. It acts as the central intelligence of the system.
Key inverter specifications for off-grid use include:
- Continuous output power (kVA or kW) — must exceed your maximum simultaneous load
- Peak/surge capacity — important for starting motors in pumps, air conditioners, and compressors, which draw high current on startup
- Battery charging capacity — determines how quickly a backup generator can recharge the batteries
- Waveform quality — quality off-grid inverters produce a pure sine wave, required for sensitive electronics and variable-speed motor loads
Inverter brands installed by OffGrid WA include Sigenergy, Victron Energy, Fronius, GoodWe, Selectronic, and Deye. All inverters installed are listed on the relevant approved product lists for compliance with Australian standards and rebate eligibility.
5. Backup Generator (Optional)
A backup generator provides power when battery reserves run low and solar production is insufficient — during extended cloudy periods, unusually high energy consumption, or seasonal periods of low solar availability.
In a properly designed off-grid system, the generator should rarely need to run. When it does, the inverter/charger automatically starts and manages the generator to recharge the battery bank, then shuts it down once an adequate state of charge is reached.
Common options include diesel generators — most practical for remote WA properties where fuel delivery is infrequent — and LPG generators. Generator sizing is based on both the battery charging requirement and the peak loads the system must support simultaneously.
6. System Monitoring
All modern off-grid systems installed by OffGrid WA include remote monitoring capability via a smartphone app or web portal. This allows you to view in real time:
- Solar generation (kW output and daily kWh totals)
- Battery state of charge
- Load consumption
- Any system alerts or faults
Monitoring platforms vary by inverter brand. During system handover, OffGrid WA walks through the monitoring setup so you know exactly how to keep an eye on your system from anywhere.
How the System Works Together
Here is the typical flow of energy through a well-designed off-grid system on a sunny WA day:
- Sunlight hits the solar panels and generates DC electricity
- The MPPT charge controller (or integrated inverter) optimises power drawn from the panels
- If the batteries need charging, power flows into the battery bank first
- Once batteries are sufficiently charged, the inverter supplies AC power directly to your loads from solar
- At night or during cloud, the inverter draws from the batteries to supply your loads
- If batteries reach a low state of charge threshold (typically 20% for LiFePO4), the system signals a low battery alert or automatically starts a backup generator
System Types
Pure Off-Grid (Stand-Alone Power System)
Completely independent of the Western Power network. Ideal for remote properties across WA where grid connection is not available or is prohibitively expensive. All power comes from solar, batteries, and an optional backup generator.
Hybrid System
Connected to the Western Power grid but with battery storage. Allows you to operate primarily on solar and battery power, with the grid available as backup. During a grid outage, the system can island and continue supplying your property from batteries. Hybrid systems on the South West Interconnected System (SWIS) are eligible for Synergy’s Distributed Energy Buyback Scheme (DEBS).
Fringe-of-Grid
Western Power has been progressively replacing unreliable fringe-of-grid connections with Stand-Alone Power Systems for eligible customers. For privately owned properties in similar locations, a privately installed off-grid system is often the most reliable and cost-effective long-term solution.
Australian Standards and Compliance
All off-grid solar systems installed in Australia must comply with AS/NZS 4509, the Australian and New Zealand Standard for Stand-Alone Power Systems. This standard covers system design requirements and sizing methodology, installation and electrical safety, component selection and performance standards, and documentation and labelling requirements.
Grid-connected solar and battery installations must also comply with AS/NZS 5033 (installation of photovoltaic arrays) and AS/NZS 4777 (grid connection of energy systems via inverters).
All electrical work must be carried out by a licensed electrician under WA’s Electricity (Licensing) Regulations 1991. OffGrid WA holds Electrical Contractor’s Licence EC: 010556.
Installers must hold current accreditation with Solar Accreditation Australia (SAA) to install systems under the federal Small-scale Renewable Energy Scheme (SRES) and claim Small-scale Technology Certificates (STCs). OffGrid WA’s installers hold SAA accreditation for both grid-connected and stand-alone power systems.
OffGrid WA is also approved under the New Energy Tech Consumer Code (NETCC), a consumer protection framework for the solar and battery industry that requires members to meet standards for transparency, fair contracts, and quality installation practices.