Retrofitting a battery - AC Vs DC Batteries
Understanding Your Options for Solar Battery Integration
Introduction
Solar energy is becoming a mainstream solution for reducing energy costs and reliance on the grid. One of the key enhancements to any solar system is the addition of a battery, which allows for energy storage and increased self-sufficiency. Whether you are retrofitting an existing solar system or designing a new installation, it is important to understand the different ways batteries can be integrated: AC-coupled and DC-coupled solutions.
Why Add a Solar Battery?
Solar batteries store excess energy generated by your solar panels, allowing you to use stored energy when the sun isn't shining. The main benefits include:
Energy Independence: Reduce reliance on the grid and gain some protection against power outages.
Cost Savings: Use stored energy when the sun goes down and during peak rate times to lower electricity bills.
Environmental Benefits: Maximise your use of renewable energy and reduce your carbon footprint.
AC-Coupled vs. DC-Coupled Battery Systems
There are two main ways to integrate a home solar battery into a system: AC-coupled and DC-coupled solutions. Each has its own benefits and considerations.
AC-Coupled Battery Systems
AC-coupled battery systems are ideal for retrofitting an existing solar setup, as they can work independently of the original solar inverter. These systems feature their own battery inverter, which converts AC electricity back into DC for storage and vice versa when discharging.
Pros:
Compatible with almost any existing solar system.
Easy to install and expand.
Works as a plug-and-play solution.
Cons:
Less efficient due to additional energy conversions.
Can only charge with surplus solar energy.
Lacks black start capability, meaning the system cannot restart during a prolonged blackout without grid power.
DC-Coupled Battery Systems
DC-coupled battery systems use a hybrid inverter that manages both solar generation and battery storage. These systems control the battery on the DC side of the solar system, which improves efficiency by reducing conversion losses.
Pros:
More efficient as energy flows directly from solar panels to battery storage.
Allows for greater potential solar panel capacity in a system.
Most hybrid inverters support backup power and black start capability, ensuring energy availability to backed up circuits even during extended outages.
Cons:
Requires replacing a standard solar inverter with a hybrid inverter.
Best suited for new installations rather than retrofits.
Retrofitting an Existing Solar System with a Battery
If you already have a solar system and are looking to add a battery, you have two main options:
AC-Coupled Battery: A simple and flexible option, provided there is sufficient excess solar energy to charge the battery.
Hybrid Inverter + Battery Upgrade: Replacing your existing inverter with a hybrid inverter allows for the benefits of a DC-coupled solution. This is the preferred option to maximise the potential of the existing solar panels.
If your current solar system is over 10 years old or too small to justify a battery, you might consider replacing it with a new hybrid solar and battery system for maximum efficiency.
Installing a New Solar and Battery System
If you are installing a new solar system and want to include battery storage from the start, you have the advantage of designing an optimised setup:
System Design: Work with a certified CEC installer to ensure the system meets your energy needs, budget and expectations.
Battery Selection: Consider factors such as battery capacity, efficiency, lifespan, and cost. Lithium-ion batteries are the preferred choice for modern installations. Remember there is a very close relationship between the time of peak loads, amount of battery storage required and excess solar PV for charging.
Monitoring & Maintenance: Most hybrid inverters offer real-time monitoring to track performance and manage energy use.
Cost and Financing Options
Adding a solar battery involves an initial investment, but various financing options are available:
Government Rebates: Synergy customers can receive up to a $5,000 rebate for battery purchases from the WA State Government.
Interest-Free Loans: The WA state government offers interest-free green loans of up to $10,000 to eligible applicants.
Green Loans from Banks: Many financial institutions offer specialised loans for solar and battery systems.
Conclusion
Integrating a solar battery into your system—whether as a retrofit or as part of a new installation—enhances energy independence, reduces electricity costs, and supports a sustainable future. While AC-coupled systems offer an easy retrofit solution, DC-coupled systems are generally more efficient and offer superior backup capabilities.
For expert guidance, we recommend consulting a Clean Energy Council (CEC) certified solar and battery installer. We can connect you with top-rated local professionals to ensure you get the best solution for your needs.