If you've recently installed solar panels or are considering going solar, you've probably heard about home battery storage systems. These devices have become increasingly popular among Australian homeowners looking to maximise their solar investment and reduce their reliance on the electricity grid. But what exactly are solar batteries, and how do they work? This comprehensive guide will walk you through everything you need to know as a beginner.
What Is a Solar Battery?
A solar battery, also known as a home battery or energy storage system, is a device that stores excess electricity generated by your solar panels for later use. During the day, when your solar panels produce more electricity than your home needs, this surplus energy would typically be exported back to the grid. With a battery, you can store this energy instead and use it during the evening, at night, or during peak electricity pricing periods.
Think of it like a large rechargeable battery for your entire home. Modern solar batteries use lithium-ion technology—similar to what powers your smartphone or electric vehicle—but on a much larger scale. These batteries are designed to charge and discharge thousands of times over their lifespan, typically 10 to 15 years.
Key Takeaway
A solar battery stores excess energy from your solar panels during the day so you can use it at night or during peak tariff times, reducing your electricity bills and grid dependence.
How Does a Solar Battery System Work?
Understanding how a solar battery integrates with your existing solar system is crucial for making informed decisions. Here's a step-by-step breakdown of the energy flow in a typical solar-plus-storage system:
During Daylight Hours
When the sun is shining, your solar panels generate direct current (DC) electricity. This electricity first powers your home's immediate needs—running your refrigerator, air conditioning, lights, and other appliances. Any excess electricity that your home doesn't immediately use flows into your battery to charge it. Once your battery is fully charged, any remaining surplus is typically exported to the grid, earning you a feed-in tariff from your electricity retailer.
During Evening and Night
As the sun sets and your solar panels stop generating electricity, your home automatically switches to drawing power from your stored battery. This means you can continue using clean, solar-generated energy even after dark. Your battery will gradually discharge throughout the evening, powering your home until it reaches its minimum charge level or until the sun rises again.
Grid Interaction
Most solar battery systems remain connected to the electricity grid. This provides a safety net—if your battery runs flat and the sun isn't shining, you can still draw power from the grid. Some advanced systems also allow you to charge your battery from the grid during off-peak hours when electricity is cheaper, then use that stored energy during expensive peak periods.
Key Specifications You Need to Understand
When shopping for a solar battery, you'll encounter several technical specifications. Understanding these terms will help you compare different products effectively:
Capacity (kWh)
Measured in kilowatt-hours (kWh), capacity tells you how much energy the battery can store. A typical Australian home uses between 15 and 25 kWh of electricity per day. However, you don't necessarily need a battery that can store your entire daily usage—you only need enough to cover your evening and overnight consumption, plus any periods when your solar panels aren't generating enough power.
Power Output (kW)
Measured in kilowatts (kW), power output indicates how much electricity the battery can deliver at any given moment. A battery with a higher power output can run more appliances simultaneously. If you want to run an air conditioner, oven, and other high-draw appliances from your battery, you'll need sufficient power output to handle the combined load.
Pro Tip
Don't confuse capacity with power output. A battery might have large capacity (lots of stored energy) but low power output (can only release it slowly), or vice versa. Consider both specifications based on how you plan to use your battery.
Depth of Discharge (DoD)
Depth of discharge indicates what percentage of the battery's capacity can actually be used. Most lithium-ion batteries have a DoD of 90% to 100%, meaning you can use nearly all of the stored energy. Some older or cheaper batteries may have lower DoD ratings, which means their usable capacity is less than the advertised total capacity.
Cycle Life
A cycle refers to one complete charge and discharge of the battery. Cycle life tells you how many cycles the battery can perform before its capacity degrades significantly (usually defined as falling below 70% or 80% of original capacity). Premium batteries typically offer 6,000 to 10,000 cycles, which translates to 15 or more years of daily use.
What Size Battery Do You Need?
Choosing the right battery size depends on several factors specific to your household:
Your energy consumption patterns: Review your electricity bills to understand when you use the most power. If most of your consumption occurs during the evening, a larger battery makes sense. If you're home during the day and use power as it's generated, you may need less storage.
Your solar system size: Your battery should be appropriately sized relative to your solar system. A general rule of thumb is that your battery capacity in kWh should be roughly equal to or slightly larger than your solar system size in kW. For example, a 6.6kW solar system pairs well with a 10kWh battery.
Your goals: Are you primarily looking to reduce electricity bills, achieve greater energy independence, or have backup power during outages? Each goal may require different battery sizing and features.
Benefits of Solar Battery Storage
Installing a solar battery offers several compelling advantages for Australian homeowners:
- Maximise self-consumption: Use more of the solar energy you generate instead of exporting it at low feed-in tariff rates
- Reduce peak-rate electricity purchases: Avoid buying expensive grid power during peak pricing periods
- Energy independence: Reduce your reliance on the electricity grid and protect yourself from rising power prices
- Backup power: Many batteries can provide essential power during grid outages (requires specific configuration)
- Environmental benefits: Maximise your use of clean, renewable solar energy
- Virtual Power Plant participation: Some battery systems allow you to earn money by participating in VPP programs
Did You Know?
The average Australian household can save between $1,500 and $2,500 per year with a well-sized solar battery system, depending on their energy usage patterns and electricity tariff structure.
Getting Started with Solar Batteries
If you're ready to explore solar battery storage for your home, here are the essential first steps:
First, analyse your current energy usage by reviewing at least 12 months of electricity bills. Look for patterns in when you use the most power and how much you're currently paying during peak versus off-peak periods. This information is crucial for determining the right battery size and calculating potential savings.
Second, if you already have solar panels, check their capacity and age. Your existing inverter may need to be upgraded or replaced to work with a battery, or you might opt for a battery with a built-in inverter. If you don't have solar yet, consider installing both systems together for a more streamlined setup.
Third, research available rebates and incentives in your state. Programs like Victoria's Solar Homes Program and South Australia's Home Battery Scheme can significantly reduce the upfront cost of battery installation. These programs often have eligibility requirements and application processes, so factor this into your timeline.
Finally, obtain quotes from multiple Clean Energy Council-accredited installers. A reputable installer will assess your specific situation, recommend appropriate products, and ensure your system is installed safely and correctly. Don't just focus on price—consider the installer's experience, warranty support, and customer reviews.
Solar battery technology has matured significantly in recent years, making it a viable and worthwhile investment for many Australian households. By understanding the basics outlined in this guide, you're well-equipped to begin your journey toward greater energy independence and lower electricity bills.