The Ultimate Guide to Solar Batteries

Solar panels are a fantastic first step towards harnessing clean energy, but what happens when the sun goes down, or when you generate more power than you immediately need? Solar batteries play a crucial role in enhancing your energy management strategy. If you’re looking for better energy independence, to reduce your reliance on the grid, or to make the most of your existing solar PV system, you’re in the right place. 

We’re passionate about helping you create an energy-efficient home that’s built for the future. This guide will walk you through everything you need to know about solar battery storage, helping you to make informed decisions.

All About Batteries 

Let's dive into the world of solar batteries and explore how they can be a significant change for your home.

Is it Worth Getting Battery Storage with Solar Panels? 

For many homeowners, adding solar battery storage is a smart move that offers a range of benefits: 

• Maximise Self-Consumption: Store the excess solar energy you generate during the day and use it in the evenings or on cloudy days. This means you’re using more of your own clean energy and buying less from the grid. 

• Reduce Electricity Bills: By using your stored solar power instead of grid electricity, you can significantly lower your energy costs. 

• Energy Independence: Gain greater freedom from fluctuating energy prices and reliance on the grid. Solar batteries put you more in control of your power. 

• Reliable Backup Power: Experience peace of mind knowing you have a backup power solution during outages. Keep essential appliances running smoothly, even when the grid goes down. 

• Environmental Benefits: Storing and using your own solar power is an eco-friendly energy choice, reducing your carbon footprint and supporting a more sustainable future. 

How Do Solar Batteries Work?  

Solar panels produce Direct Current (DC) electricity. This DC electricity can either be used to charge your solar battery or converted into Alternating Current (AC) and used immediately by appliances in your home. 

Inside a typical lithium-ion solar battery, the process involves the movement of lithium ions. During charging, electrical energy from your solar panels forces lithium ions to move from the cathode (positive electrode) to the anode (negative electrode), passing through an electrolyte. This stores energy. When you draw power from the battery (discharging), these ions flow back to the cathode, releasing the stored electrical energy. 

How do solar batteries power your home?  

When your solar panels aren’t generating enough power (e.g., at night or on a very cloudy day), or if you simply want to use your stored energy, the battery discharges. The stored DC electricity from the battery is sent to an inverter (which might be the same one your solar panels use, or a separate one for the battery), which converts it into AC electricity that your home appliances can use. 

How are solar batteries charged?  

Solar batteries are charged by the surplus electricity generated by your solar panels. When your panels produce more power than your home is currently consuming, this excess energy is directed to charge the battery. A charge controller ensures the battery is charged optimally and prevents overcharging. 

Do solar batteries recharge themselves?  

No, when your solar PV system is producing more power than you need, that excess is used to replenish the battery. They can also be scheduled to recharge during “off Peak” tariff times to further reduce the cost of your energy usage. All these parameters can be tailored to the individual owners' requirements.  

What happens to solar power when batteries are full?  

Once your solar battery storage is fully charged and your home's energy needs are met, any further excess solar power generated typically has two main paths: 

• Export to the Grid: If your system is grid-tied and you have an agreement with your utility provider (like the Smart Export Guarantee - SEG), the surplus energy can be exported to the national grid. You may receive a payment or credit for this exported energy. 
• Curtailment: If you can't export it (or choose not to), your solar inverter may reduce its power production (curtailment) to prevent overloading the system. Modern inverters are designed to manage this automatically. 

AC-Coupled vs. DC-Coupled Battery Systems  

When integrating a battery into your solar system, there are two main approaches: 

DC-Coupled Battery Systems: 

• Solar panels generate DC power, which goes to a charge controller that directly charges the DC battery. When power is needed, it flows from the battery to an inverter, which converts it to AC for your home.  

• Pros: Generally, more efficient as only one main inversion (DC from battery to AC for home) is required for stored energy, leading to round-trip efficiencies of up to 97.5%. Often a good choice for new, integrated solar and storage installations. 

• Cons: Can be more complex and potentially more difficult to install or configure into existing solar systems. 

AC-Coupled Battery Systems: 

• Solar panels generate DC power, which is immediately converted to AC by a solar inverter for your home. To charge the battery, this AC power is then converted back to DC by an inverter/charger that comes with the battery system. When the battery discharges, this DC power is inverted again to AC for your home. 

• Pros: Easy integration with existing solar PV systems by connecting to the home's AC supply. 

• Cons: Involves multiple inversions (solar DC to AC, then AC to DC for battery charging, then battery DC back to AC for use), leading to slightly lower round-trip efficiency, typically around 85-90%.  

Choosing between AC and DC coupling depends on whether you're installing a new system or retrofitting, your desired efficiency, and specific site conditions. We can help you determine the best fit. 

What Are the Different Types of Solar Batteries?  

While various battery chemistries exist, the most common and generally recommended type for residential solar storage is the Lithium-ion battery. Within this category, there are several sub-types, with Lithium Iron Phosphate (LiFePO4) being particularly popular for home energy storage. 

Lithium-ion Batteries (e.g., LiFePO4, NMC):  

• Pros: High energy density (store more energy in less space), long battery lifespan, good depth of discharge (DoD) (meaning you can use a larger percentage of the battery’s capacity), and generally maintenance-free. LiFePO4 batteries are known for their excellent thermal stability, safety, and longer cycle life. 
• Cons: Can have a higher upfront solar battery cost compared to older technologies, though prices are decreasing.  

Lead-Acid Batteries:  

• Pros: A more established technology with a lower initial cost. 

• Cons: Shorter lifespan, lower DoD (typically around 50%), bulkier, require more maintenance, and can be less environmentally friendly in terms of disposal. For these reasons, they are less commonly used in modern residential solar storage systems. 

At 21 Degrees, we focus on providing high-quality, reliable lithium-ion solar battery solutions that offer the best performance and longevity for your home. We can advise on the specific battery technologies that best suit your needs and ensure a neat, professional installation. 

How to Choose the Right Battery Size 

Selecting the appropriate battery capacity (measured in kilowatt-hours, kWh) is crucial for getting the most out of your solar battery storage system. Here are key factors to consider: 

• Your Daily Energy Consumption: How much electricity do you typically use in a day? Look at your energy bills, particularly for periods when you’d rely on battery power (e.g., evenings). 

• Your Solar System's Generation Capacity: How much electricity do your solar panels produce, and how much of that is typically surplus? 

• Your Goals for Battery Storage: 

• Maximising Self-Consumption: You might want a battery that can store enough to cover your evening and nighttime usage. 

• Backup Power: If backup power is a priority, consider how many essential appliances you want to run during an outage and for how long. This will influence the required capacity for your load shedding battery backup or emergency solar power storage.  

• Depth of Discharge (DoD): This refers to the percentage of a battery's total capacity that can be safely used. For example, a 10-kWh battery with a 90% DoD provides 9 kWh of usable energy. Lithium-ion batteries typically have a high DoD (90-100%). 

• Budget: Battery costs vary by size and type. It’s about finding the right balance between capacity and affordability. 

• Available Space: Ensure you have adequate space for the physical battery unit. 

We understand that sizing a battery can seem complex. That's why we're here to help you assess your needs and recommend the perfect battery size for your home.

What Are the Environmental Benefits of Solar Battery Storage? 

Pairing solar panels with battery storage significantly amplifies the positive environmental impact of your solar PV system. Here’s how: 

• Increased Use of Renewable Energy: Batteries allow you to store your clean solar energy, meaning you use more of it and rely less on grid electricity, which may be generated from fossil fuels. This directly reduces your household's carbon emissions. 

• Reduced Reliance on Peaker Plants: During times of high electricity demand, utility companies often fire up "peaker plants," which are typically less efficient and more polluting. By using your stored solar energy during these peak times, you help reduce the need for these plants. 

• Grid Stability: As more homes adopt solar and storage, it can contribute to a more stable and resilient electricity grid, facilitating the integration of more renewable energy sources overall. 

• Promoting Eco-Friendly Energy Solutions: Choosing solar battery storage for your home is a tangible step towards a more sustainable lifestyle and supports the broader transition to cleaner energy systems. It’s a commitment to improving the planet, one home at a time.

Benefits and Considerations of Solar Batteries  

Let's break down the pros and cons to give you a balanced view: 

While the initial investment is a key consideration, the long-term financial and environmental return on investment (ROI), coupled with energy security, makes solar batteries an increasingly attractive option for homeowners. 

Installing Solar Batteries 

Understanding the installation process and what’s involved in keeping your system running smoothly is important. 

How Is a Battery System Set Up?  

Setting up a solar battery system involves more than just placing a box on the wall. Here’s a general overview: 

• Site Assessment & System Design: A qualified installer will assess your property, existing solar setup (if any), energy needs, and where the battery can be safely and effectively installed. They'll design a system tailored to you. 
• Mounting the Battery: The battery unit will be securely mounted, often on a wall in a garage, utility room, or sometimes externally, depending on the battery type and manufacturer's specifications. 
• Electrical Wiring: The battery needs to be wired into your solar PV system and your home's electrical system. This includes connecting to an inverter (either a hybrid inverter that manages both solar and battery, or a dedicated battery inverter if it's an AC-coupled system). A charge controller may also be part of a DC-coupled setup.  
• System Configuration & Commissioning: Once everything is connected, the installer will configure the system settings, including charge/discharge parameters, and ensure everything is communicating and operating correctly and safely. 
• Inspection and Handover: A final inspection may be required, and the installer will walk you through how your system works, how to monitor it, and any maintenance tips. 

It’s crucial that certified and experienced professionals install your solar battery system. At 21 Degrees, we pride ourselves on our neat and meticulous installations, ensuring your system is not only efficient but also safely and correctly integrated into your home.  

How to Maintain a Solar Battery System  

One of the great things about modern solar battery storage systems, particularly lithium-ion types, is that they are generally very low maintenance. However, a few simple steps can help ensure optimal performance and longevity: 

• Monitoring: Keep an eye on your system’s performance through its monitoring app or display. This can help you spot any unusual behaviour early on.
• Keep it Clean and Ventilated: Ensure the area around the battery is kept clean and free from obstructions to allow for proper ventilation and prevent overheating. 
• Visual Checks: Periodically check for any visible signs of damage or loose connections (though tampering with the unit itself should only be done by a professional). 
• Software Updates: Some battery systems may have software that requires occasional updates. Your installer will advise if this is user-manageable or part of a service check. 
• Professional Check-ups: While not always mandatory, having a professional check your system every few years can be beneficial to ensure everything is running optimally. 

Always refer to the manufacturer's specific maintenance guidelines for your battery model. 

What Is a Battery's Lifespan?  

The lifespan of a solar battery is a key consideration. For modern lithium-ion batteries, you can typically expect a lifespan of 10 to 15 years. Most high-quality batteries come with a warranty that guarantees performance for a certain number of years or charge cycles (whichever comes first). 

Several factors can influence a battery’s lifespan: 

• Cycles: How many times the battery is fully charged and discharged. 
• Depth of Discharge (DoD): Regularly discharging a battery to its maximum DoD can put more stress on it than shallower discharges, though modern batteries are designed to handle their specified DoD.  
• Operating Temperature: Extreme temperatures (both hot and cold) can affect battery health and longevity. Most systems have built-in thermal management. 
• Usage Patterns: How heavily and how often the battery is used. 
• Battery Chemistry and Quality: Higher quality batteries from reputable manufacturers generally last longer. 

While batteries do degrade over time (their capacity to hold a full charge will gradually decrease), a good quality solar battery should provide many years of reliable service.  

Take Control with 21 Degrees 

Ready to unlock the full potential of your solar energy system and enjoy greater energy independence? Adding solar battery storage is a powerful step towards a more resilient, cost-effective, and sustainable home.  

At 21 Degrees, we’re not just about supplying products; we’re your partners in creating optimal energy solutions. We provide: 

• Expert Advice: We’ll help you understand your options and choose the right battery system for your specific needs and budget.  

• System Design: Our team designs efficient and effective solar and storage solutions tailored to your property.  

• Quality Products: We work with leading battery manufacturers to offer reliable, high-performance solar battery storage systems.  

• Neat, Professional Installation: Our experienced in-house installers ensure your system is set up correctly, safely, and cleanly.  

• Ongoing Support: We’re here to answer your questions and provide support even after your system is up and running.  

Let us help you take the next step in your energy journey. Contact 21 Degrees today to discuss your solar battery options and get a personalised quote. 

Further FAQs  

Can I add a battery to my existing solar panel system? 

Yes, in most cases, you can add a solar battery to an existing solar panel system. AC-coupled battery systems are particularly well-suited for retrofitting as they are easier to integrate with your current setup. We can assess your existing system and advise on the best way to add storage. 

How long does a solar battery last during a power outage? 

This depends on several factors: the battery’s capacity (kWh), how much power you’re using during the outage, and which appliances you choose to run. A well-sized battery can keep essential appliances like lights, fridges, and internet routers running for several hours, or even longer if usage is managed carefully. 

What’s the typical Return on Investment (ROI) for solar batteries? 

The ROI for solar batteries varies based on factors like your electricity consumption patterns, the price you pay for grid electricity, the cost of the battery system itself, and any incentives available. While the primary benefits are often seen in increased self-consumption and energy security, we can help you estimate the potential financial returns for your specific situation. 

Do I need a charge controller for my solar battery? 

A charge controller is essential for regulating the power from your solar panels to your batteries, preventing overcharging and optimising the charging process. In DC-coupled systems, this is either a distinct component or integrated into each battery module. In AC-coupled systems, the battery's integrated inverter/charger typically handles this function.  

Are solar batteries safe for home use? 

Yes, modern solar batteries, especially lithium-ion types like LiFePO4, are designed with multiple safety features and are very safe for home use when installed correctly by qualified professionals. They include systems to manage temperature, voltage, and current to prevent issues.

Further information can be found here.