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Solar batteries - what’s right for you?

Jan 27, 2022

According to the Department of Industry, Science, Technology and Resources there are now more than three million rooftop solar PV systems installed across Australia - that’s a global record and equivalent to around 30% Australian of homes!

With this high uptake it’s exciting to watch as the Australian solar industry takes the next steps in its evolution. Consumers are beginning to embrace concepts like Virtual Power Plants (VPPs) and are keen to include solar batteries with their solar panel installations or add battery storage to their existing solar panel setup.

So what do you need to know when considering a solar battery for your rooftop solar PV system?

Types of solar batteries in today’s market

Lithium-ion batteries

Product examples: Tesla, LG Chem, BYD and Sonnen.

Lithium-ion solar batteries are currently the most common type of battery being used in solar and use a similar technology to other high-tech devices in our lives - smartphones and laptops.

The reasons for their popularity include:

  • resilience in a wide range of ambient temperature conditions,

  • a very high discharge capacity (80-90%),

  • capacity for several thousand charge-discharge cycles over its lifetime.

  • high energy density

Lead solar batteries

Product example: Ecoult UltraBattery.

The lead acid or AGM solar battery uses the same technology as the traditional car battery and is more commonly used for off grid solar systems. It’s advantage is it is a relatively cheap and well-understood technology with already established disposal and recycling processes. However most lead-acid solar batteries are bulky, sensitive to heat (which can reduce the lifespan of the battery) and have a slow charge cycle. Advanced lead-acid batteries such as the Ecoult UltraBattery aim to improve these shortcomings.

Flow batteries

Product example: Redflow’s ZCell

Flow batteries use a pumped electrolyte and chemical reactions to charge, store and release the sun’s energy. This is the newest technology in the solar battery industry with exciting advantages like:

  • the ability to be discharged to 100% of capacity,

  • no loss of charge over time,

  • they don’t lose capacity over time,

  • resilience to high ambient temperatures (however they don’t tolerate cold temperatures below 15 degrees C)

The main downside of flow batteries is that they do require frequent maintenance and during maintenance are put out of service. They are also the most expensive upfront cost of the mentioned technologies.

Industry terminology

Understanding the industry jargon will help in your journey of choosing the most appropriate battery for your solar panel installation:

  • Capacity: this tells you how much the battery can store and is measured in kilowatt-hours (kWh).

  • Depth of discharge (DoD): This is how much of your battery’s capacity can be discharged without shortening the life span of the battery by allowing the charge to run too low. The higher the DoD, the more of the battery’s charge space will be available for use.

  • Power: refers to a battery's output capability. The amount of power a solar battery can deliver is measured in kilowatts (kW).

  • Round-trip efficiency: this is the difference between the amount of energy used to charge the battery and the available amount of energy. A higher round-trip efficiency is better.

What to consider when choosing a solar battery for your home

Some questions to think about when considering a solar battery include:

  • What is the total installed cost of your solar energy storage system versus the expected output over its lifetime?

  • What system best suits your tariff structure? Whenever energy is diverted to your solar battery you forgo your feed-in tariff from sending power into the grid. As industry feed-in tariffs drop this balance between feeding the grid and saving power for yourself will help determine the right time for you to invest in solar energy storage.

  • Ideally aim for a solar battery with a depth of discharge at least 80% for on-grid applications and round-trip efficiency around 80%.

  • Do you have an appropriate space to install the battery? What is the ambient temperature in the area suitable for your solar battery?

  • Can the battery you are considering store and supply enough energy for your needs? What is your household’s daily power use and how much extra electricity does your solar installation generate? How much independence do you want from the grid? Here is a simple calculator to help estimate your family’s energy needs. An even more accurate method is to look through your past energy bills.

  • Is the solar supplier a reputable company that can meet any warranty claims? Components of a solar installation are a long-term home investment and warranty periods easily range from 10 - 25 years. This is worthless if the company that made the products and provides the warranty has gone out of business in this timeframe. Innovate Energy makes it a policy to only recommend and install quality components from reputable suppliers we trust will be here for the long-haul.

  • Should you increase your home insurance coverage after installing a solar battery system? Remember you solar panel installation is part of your house and should be covered on your home insurance.

Solar battery costs and possible rebates

The cost of a solar battery varies considerably depending on the size you require and the battery technology you choose. As a rough guide:

  • 6kWh battery - $5-$9,000

  • 10kWH battery - $9-$14,000

  • 13kWh battery - $10-$18,000.

These are ballpark figures. For a customised quote that takes into account your personal energy needs both now and moving into the future, get in touch today.

The good news is that many states are offering rebate and energy trading schemes to help people afford sustainable energy solutions like solar batteries. The small-scale technology certificate (STC) incentive for batteries applies Australia-wide and energy companies are offering various VPP programs that can help reduce the cost of installing a solar battery.

Additionally, here are some rebate schemes from Australian States:

NSW: Empowering Homes solar battery loan offer

VIC: Solar Homes Program

SA: Home Battery Scheme

ACT: Next Gen Battery Storage Program and ACT Sustainable Household Scheme

NT: Home and Business Battery Scheme

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