If you’ve started researching solar power—either for your home or your business—you’ve likely encountered the term “Balance of System” (often shortened to “BOS”). It might sound a bit technical, but it’s actually a simple concept. Balance of System refers to all the parts and components in a solar power system aside from the solar panels themselves. Without these essential elements, your shiny new panels wouldn’t do you much good. Let’s break down what BOS means, why it matters, and how it affects your solar energy setup.
What is Balance of System?
When you install a solar power system, your main focus might be on the solar panels—also called “modules.” But panels alone aren’t enough to generate usable electricity. A solar array needs various additional components to function smoothly and safely. These extra components—including mounting structures, inverters, wiring, and other equipment—collectively make up the Balance of System.
One way to think about it is: The BOS ‘balances’ or completes the system, so that the power coming from your solar panels can actually be used in your home, business, or fed back into the electricity grid.
Breaking Down BOS Components
While every solar system has its own design and requirements, here are the most common BOS components you’ll encounter:
- Mounting and Racking Hardware
- Purpose: To secure solar panels in place, whether on your rooftop, a ground-mounted frame, or a commercial building’s flat roof.
- Why It Matters: Proper mounting ensures panels stay in place under wind and weather conditions. It also helps maximise the angle and orientation for the best possible sunlight exposure.
- Inverters
- Purpose: Convert the direct current (DC) electricity produced by your panels into alternating current (AC), which is what most homes and businesses use.
- Why It Matters: Without an inverter, your solar panels are essentially just generating electricity you can’t use. For those with battery storage, you might also encounter hybrid inverters that manage both solar energy generation and battery charging/discharging.
- Electrical Wiring and Cabling
- Purpose: Connect solar panels together and then link them to the inverter and, eventually, your electrical switchboard.
- Why It Matters: Quality wiring minimises power loss and ensures safety. The right gauge (thickness) of cable is crucial to handle the current flowing through the system.
- Safety Devices (e.g., Disconnects, Fuses, and Breakers)
- Purpose: Allow you to safely shut down the system if needed and protect against electrical faults or overloads.
- Why It Matters: Ensuring your system meets electrical codes and Australian Standards is critical for safety and to maintain your warranty and insurance conditions.
- Monitoring and Control Systems
- Purpose: Track how much energy your panels are generating, monitor system performance, and alert you (or your installer) if anything goes wrong.
- Why It Matters: Real-time data can help you spot issues early and understand when your system is performing optimally.
- Battery Storage (Optional)
- Purpose: Store excess solar energy produced during the day so it can be used at night or during peak hours.
- Why It Matters: Battery storage can increase your energy self-sufficiency, reduce reliance on the grid, and potentially lower electricity bills. For businesses, it can also provide backup power in case of outages, protecting critical operations.
Balancing Residential vs. Commercial Needs
Homeowners typically require smaller systems designed for rooftop installation. The BOS components might be relatively straightforward: a roof mount, a single inverter, and standard wiring leading to your home’s switchboard.
Commercial installations, on the other hand, can be larger and more complex. They might involve multiple inverters, extensive racking solutions, and intricate monitoring systems. For instance, a business with significant daytime energy usage might opt for a battery storage system to offset peak demand charges or ensure continuity during power outages.
The Role of Net Metering and Feed-In Tariffs
In Australia, many energy retailers offer feed-in tariffs, which allow solar system owners to export excess electricity back into the grid and earn credits on their power bills. This arrangement is often referred to as net metering. When your system produces more solar power than you use, that surplus is fed to the grid, and you earn a certain rate (tariff) per kilowatt-hour.
- How BOS Fits In: Your system’s BOS components, especially the inverter and metering setup, help ensure that exported power is accurately recorded and that you’re properly credited by your electricity retailer. If you have a battery, some inverters can automatically decide whether to store solar power in the battery or export it to the grid, depending on tariffs and electricity demand in your home or business.
Why BOS Matters: Practical Implications
- System Reliability and Safety
A robust BOS design keeps your system running safely for its entire lifespan. Properly sized inverters, cables, and breakers reduce the risk of malfunctions, fires, or performance drops. - System Efficiency
High-quality BOS components can make a real difference in how efficiently your system converts sunlight into usable energy. Subpar wiring or a poorly matched inverter can lead to significant energy losses over time. - Cost Considerations
As solar panel prices continue to decrease, BOS costs have become a larger portion of the overall system price. By choosing efficient and durable BOS components, you’ll enjoy better long-term performance and fewer maintenance issues, offsetting the initial investment. - Future Proofing
If you’re thinking about adding battery storage later, or planning on expanding your system, it’s wise to select BOS components (like inverters) that can handle future upgrades.
Can a System Be “Unbalanced”?
If your BOS components are inadequate or poorly matched to your solar panels, it can create an “unbalanced” system. For example:
- Using an inverter that’s too small means you could be missing out on potential energy generation during peak sun.
- Installing an improper racking system can lead to loose panels or sub-optimal angles, reducing your energy harvest.
- Undersized cables or connectors can cause voltage drops and safety hazards.
When everything is sized correctly and installed properly, your BOS ensures that the power generated by your panels is utilised effectively, maximising both energy production and longevity of the system.
Final Thoughts
Balance of System components may not be as glamorous as solar panels themselves, but they’re just as important for anyone considering a switch to solar. Whether you’re a homeowner looking to cut energy costs or a business owner wanting to reduce your carbon footprint, understanding BOS will help you make more informed decisions about your solar investment. A well-chosen, well-designed BOS ensures you get the most out of your panels, improves your return on investment, and provides the flexibility to adapt to future energy storage options or policy changes.
If you’re exploring solar power further, be sure to talk to reputable installers about the quality and compatibility of all BOS components—after all, it’s not just the panels that make the magic happen!
Disclaimer: This article provides general information only and is not a substitute for professional advice. Please consult with a certified solar installer or licensed electrician for guidance specific to your situation. In Australia, electrical work—including solar installations—must be completed by licensed electricians or accredited installers in accordance with local regulations.