Will I get a rebate on my solar battery?
Eligible Victorian households that install a qualifying solar battery to an existing solar PV panel system can now access a rebate through the Victorian Government’s Solar Homes Program.
Which solar battery do I need?
When it comes to choosing the right battery for your home, it’s important to consider not only the type of battery – including the chemistry, size, cycle life, functionality and warranty – but also your home’s energy habits – including how much electricity you use, whether you value blackout protection and your budget. A good solar battery installer will work with you to identify and design the right system for your home.
Solar battery chemistry
Common types of battery chemistries include:
Lithium-ion – li-ion batteries are lightweight and compact, can be efficiently charged and have very long lifespans. For most residential systems they are the best option, so many installers, like RACV Solar, only offer li-ion batteries. The two most common li-ion varieties currently sold are lithium-ion phosphate (LFP or LiFePO4) and lithium nickel manganese cobalt oxide (NMC). LFPs are considered safer because NMCs can overheat if discharged too quickly.
Lead-acid - until recently, most home batteries were ‘flooded’ lead-acid; they have since been replaced by sealed lead acid (SLA) batteries for additional safety. These batteries are mostly used in off-grid solar systems.
Flow - ‘flow’ batteries use liquids to store energy. Although they are safe, easily maintained, and can store charge for long periods, they currently have a very limited range in the residential market.
Solar battery size (and depth of discharge)
Solar battery size is measured in kilowatt-hour (kWh) units. You should match your battery’s size to your solar panel array: smaller for a small-scale panel set-up, and larger for a more comprehensive system. Keep in mind that the average Australian household consumes 16 kWh of electricity per day, with two-thirds consumed during non-daylight hours (when solar panels cannot generate electricity). Therefore, a 10 kWh battery will have almost enough capacity to provide your household’s energy needs if fully drained. Any energy you use past your battery’s capacity will be purchased from the power grid.
Keep in mind that solar batteries do not discharge to their full capacity, because that would shorten a battery’s lifespan. Instead, each battery has a ‘depth of discharge’: an amount beyond which a battery will not discharge. For example, lithium-ion batteries typically discharge 90 to 95 per cent of its total capacity. Therefore, if a battery is listed as 10 kWh, it may really supply only 9.5 kWh if its depth of discharge is 95 per cent.
Solar battery cycle life (and warranty)
A solar battery’s ‘cycle life’ is a figure that details how many times the battery can charge and discharge before it degrades. Standard cycle life is currently around 6,000 cycles – that's a daily charge/discharge over 10 years. As a result, most solar battery warranties are valid for 10 years.
Solar battery functionality
Make sure that your solar battery can do everything you need it to. If you require blackout protection to support your household during a power outage, for example, you will need to choose a battery with that ability. Other special functions may include using local weather data from online services to predict when the cheapest time is to charge the battery.