Determining the right size for an off-grid solar system is critical to ensuring a reliable energy supply year-round, especially during winter when sunlight is limited. This guide will walk you through the key factors to consider, including solar panel types, popular brands, advancements in manufacturing, STC rebates, system sizing and the difference between AC and DC coupling.
Understanding Solar Panel Cell Types
Solar panels are built using photovoltaic (PV) cells, and two main types dominate the market:
P-Type Cells:
- Historically the most common, P-type cells use boron as the doping agent.
- Pros: Cost-effective and widely available.
- Cons: Prone to light-induced degradation (LID), which can reduce performance over time.
N-Type Cells
- Now the industry standard, Made with phosphorus doping, these cells are gaining popularity due to their efficiency and longevity.
- Pros: Higher efficiency, better performance in low-light conditions, and less prone to LID.
- Cons: Slightly higher cost but offset by better long-term reliability.
Types of Solar Panels
Monocrystalline Panels:
- Made from a single silicon crystal, these panels offer the highest efficiency and sleek appearance.
- Ideal for systems where space is limited.
Polycrystalline Panels:
- Made from multiple silicon crystals, these are slightly less efficient but more affordable.
- Suitable for larger setups where space is not a constraint.
Bifacial Panels:
- Capture sunlight on both sides, increasing energy generation.
- Excellent for reflective or open installations, though they require specific mounting for optimal performance.
Thin-Film Panels:
- Lightweight and flexible, often used in niche applications.
- Lower efficiency compared to crystalline panels, making them less common in off-grid systems.
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Commonly Used Solar Panel Brands
Trina Solar: Founded in 1997, Trina Solar has been a global leader in solar technology for over 25 years. Operating in Australia for more than a decade, they are renowned for producing high-quality and reliable panels, with cutting-edge advancements like N-type cells. Their products are well-suited for both residential and commercial applications, backed by strong warranties and a solid local presence.
Jinko Solar: Established in 2006, Jinko Solar has quickly become one of the largest and most trusted solar panel manufacturers in the world. They’ve been active in the Australian market for over 10 years, offering cost-effective, durable panels that cater to a wide range of system sizes and budgets. Their local operations include strong distribution networks and service support, making them a popular choice for off-grid and grid-connected systems alike.
JA Solar: Founded in 2005, JA Solar is recognised for its consistent performance and commitment to innovation. They’ve been a key player in the Australian market for nearly as long, providing panels known for their efficiency and reliability. JA Solar’s panels are ideal for diverse applications, from small residential setups to large-scale industrial systems, and their reputation for quality has made them a favorite among solar professionals.
Why These Brands? Over the past few years, manufacturing standards have drastically improved. Automated production lines, rigorous quality control, and advancements in materials mean modern panels are more efficient, reliable, and durable than ever. This has resulted in warranties reaching 30 years for performance and 25 years for product defects.
Quondong Station - Off-grid Power | Cabinet - Featuring 12kW Solar, 15kVa Inverters & 25kWh Battery
How STCs Make Off-Grid Solar More Affordable
Small-scale Technology Certificates (STCs) play a significant role in reducing the upfront cost of off-grid solar systems. These rebates are available for both grid-connected and off-grid setups and are calculated based on your system's size, location, and deemed energy output over 6 years (Years remaining at time of blog). For instance, a typical 6.6kW system in Zone 3 (most of southern Australia) could qualify for around 90 STCs, translating to a rebate of $3,150–$3,600 at current market rates.
However, claiming STCs isn’t just about using certified equipment—it also requires installation by a accredited installer and designer. The Clean Energy Regulator mandates that all solar systems, whether grid-connected or off-grid, must be installed by a technician accredited by the Solar Accreditation Australia (SAA). For off-grid systems, the installer must hold specific stand-alone power system (SAPS) accreditation, ensuring they are qualified to design and install complex setups with batteries.
At MyEnergy, we ensure all our off-grid systems are certified to maximise STC benefits and meet all compliance requirements. With our licensed team holding SAPS accreditation, you can trust your installation will be eligible for rebates, ensuring you save while transitioning to reliable, renewable energy. Whether you're installing a small residential system or a larger commercial setup, STCs make off-grid solar systems more accessible and affordable than ever.
Sizing an Off-Grid Solar System
Focus on Winter Sizing:
- Solar systems must be designed to handle the shortest days of the year when sunlight is minimal. In Australia, this typically means sizing the system to provide reliable power during June and July.
Key Factors to Consider:
- Daily Energy Load: Total energy consumption, typically measured in kilowatt-hours (kWh) per day.
- Battery Capacity: Size your battery bank to provide autonomy for periods of poor weather.
- Solar Panel Capacity: Enough to fully charge batteries and meet daily loads, even on shorter winter days.
Rules of Thumb for Australia:
- For Every 1kWh of Daily Load: Install 1.5–2kW of solar panels.
- Battery Storage: 1.5–2 times the daily load in kWh. For example, a 10kWh daily load would need 15–20kWh of battery storage.
- Winter Peak Sun Hours: Plan for around 2–4 hours of sunlight per day, depending on your location.
AC vs. DC Coupling
AC Coupling:
Solar panels generate DC power, which is converted to AC using an inverter before being stored in the batteries.
Common in hybrid systems where grid backup or generators are used.
Pros: Easier to retrofit and allows for AC transmission.
Cons: Slightly less efficient due to additional conversion steps.
DC Coupling:
Solar panels directly charge the batteries through a charge controller, minimising conversion losses.
Ideal for off-grid systems where efficiency is a priority.
Pros: Higher efficiency, simpler system design.
Power Systems Should Be Unique & Tailored To The Energy Usage Of That Property
Every System Is Different
When it comes to off-grid solar systems, there’s no such thing as a one-size-fits-all solution. Every property, location, and energy need is unique, and designing a system that performs reliably requires careful consideration of several factors:
Energy Usage Patterns:
Some homes have consistent energy demands, while others experience spikes, such as powering irrigation pumps on a farm or running air conditioning during summer.
Understanding your daily and seasonal energy use is the foundation of system design.
Location and Sunlight Hours:
A property in Far North Queensland will have significantly more sunlight hours than one in southern Tasmania. Systems must be sized to account for these regional differences, especially in winter when sunlight is limited.
Battery and Backup Requirements:
The size and type of battery bank depend on how much storage you need and whether you want backup power for cloudy days or extended outages.
Load Type:
Different appliances and equipment (e.g., motors, refrigerators, or electronics) have specific power demands. Systems must be designed to handle these loads, including surges during startup.
Future Expansion:
Many customers start with a small off-grid system and expand it over time as their needs grow. Ensuring the system is scalable from the beginning saves time and money in the long run.
Why Choose MyEnergy Engineering?
At MyEnergy, we’ve been designing and installing off-grid solar systems for over a decade. Our team understands the unique challenges of remote power systems, from selecting the right solar panels to optimising battery storage and integrating advanced equipment like Victron inverters.
With our expertise, you can trust that your system will be tailored to meet your energy needs, even in the harshest conditions. Contact us today to start planning your off-grid journey with confidence!
