Solar battery storage for beginners


The energy market is rapidly changing, and solar storage units, also known as ‘solar batteries’, are a large part of this. More and more Aussies are installing solar batteries to complement their rooftop solar, allowing them to store the electricity generated by their solar for use later on or to export to the grid. If you are considering installing a solar battery, then this is your starting point. In this article, we take you through the basics, including what a solar battery is, where to buy one, how much they cost, and how to get the best bang for your buck.

What is a solar battery?

Solar battery storage units store electricity generated by your solar panels (or other renewable generator) to use later on, even when the sun goes down.

Ordinarily when electricity is generated by solar panels that is not immediately used by the house, it is diverted to the energy grid. In exchange, the customer receives a ‘feed-in tariff’, which is a small rebate on your bill of about 5c to 20c per kWh of solar power exported to the grid. Since solar panels generate the most electricity through the day when no one is home to use it, the majority of solar power is exported to the grid.

A solar battery lets you instead capture the electricity generated by your solar panels and use it for yourself later on. Most customers will save money by using their home-grown solar power instead of electricity from the grid. This is because the price of grid electricity (20-35c/kWh) exceeds the standard feed-in tariff rate they would receive for exporting the power instead of using it (5-20c/kWh).  If however you installed panels some time ago and are eligible for a state-funded ‘premium feed-in tariff’, then you might find it better to export all electricity regardless. Solar batteries also allow customers to take advantage of time of use feed-in tariff and save even more on power. This way, customers can export power in peak demand periods to receive the highest feed in tariff.

What solar batteries are available in Australia?

You have probably heard of the Tesla Powerwall, but there are loads of other options on the market as well. This includes the likes of Redflow and Aquion who have developed unique technologies to deliver what they consider to be a superior battery. Keep in mind however that the solar battery boom is just getting started, so you can expect there to be more options to choose from in the future.

To see a list of some of the most notable batteries on the market right now, click here.

 Types of battery

Not all batteries are the same, in fact, there are several types, each with their own pros and cons. The most common types of battery are Lithium-ion, Flow and Lead Acid, however new technologies are constantly being developed.

Lithium-Ion battery

Lithium-ion batteries are the most common type of battery on the market, thanks to popular brands like the Tesla Powerwall 2. Lithium-ion batteries are durable and can be discharged heavily, however they do degrade severely.

Pros Cons
  • Durable and can stored outdoors
  • Often last in excess of 10 years
  • Have a deep depth of discharge – up to approximately 95%
  • Degrades to about 60% capacity at end of life
  • Lithium is difficult to recycle and potentially harmful to the environment.

Flow Battery

Flow Batteries using flowing electrolytes such as bromide or zinc to store and release electricity. The Redflow ZCell and the Imergy Energy Storage Platform (ESP) are two examples of this technology.

Pros Cons
  • Operate well in high temperatures
  • Can be discharged to 100%
  • Don’t lose capacity as quickly
  • Expensive relative to other types of battery
  • Often have a shorter life than lithium
  • Doesn’t operate well in the cold

Lead Acid

Lead Acid batteries are somewhat of a dinosaur in the solar battery space. They are relatively cheap, however they don’t last nearly as long, nor as they as efficient as lithium or flow batteries.

Pros Cons
  • Relatively affordable
  • Many companies recycle lead-acid
  • Bulky units
  • Low efficiency
  • Shorter lifespan

How much do solar batteries cost?

A new solar battery will usually cost $2,000 to $20,000, depending on the size and make of the model. Smaller batteries, such as the 1.2kWh Enphase storage unit, cost $2,000 including installation, while larger batteries, such as Tesla’s 13.2kWh Powerwall 2, will cost $8,800 plus installation.

The below list provides the expected price of certain residential solar storage systems, though bear in mind prices may vary in some areas.

List of solar battery prices

Solar battery model Capacity Price
Enphases AC Battery 1.2kWh $2,000*
Aquion Aspen 2.2kWh $2,300
SolaX Lead Carbon 6kWh $6,700
BYD Mini ES 3.75kWh $8,400*
Tesla Powerwall 2 13.2kWh $8,800
LG Chem Resu 10 9.8kWh $8,800
Ampetus Energy Pod 14.4kWh $11,450
Redflow Z Cell 10kWh $12,600
Fronius Solar Battery 12kWh $15,500
Megallan HESS 12.8kWh $20,200
Zen Freedom Powerbank 16kWh $22,350*

*Includes Installation

As you can see, solar home storage isn’t exactly cheap – in fact it’s unclear if the savings a battery can produce will even justify its costs. That said, the price of home solar storage has tumbled in recent years and it’s expected this trend will continue. If a solar battery looks a little out of your budget right now, be sure to check prices every six months or so.

Can I go ‘off-grid’ if I have a battery?

While it is true that solar batteries help homes become more energy self-sufficient, the technology is still some way off allowing most households to affordably exit the grid entirely.  This is because most storage batteries only have capacity to meet half a home’s daily energy needs.

If your heart is set on going off grid, then you would require a large solar array and at least 20 kWh of battery storage capacity. You will also need a backup diesel generator for those rainy days when your solar isn’t working.

Battery Specifications

Depth of Discharge: Most solar batteries are unable to entirely discharge without being damaged. The ‘depth of discharge’ is a metric that describes how much of the battery’s power (in percentage) can be discharged.

Storage (kWh):  The storage capacity of a battery is measured in kilowatt-hours (kWh). There are two types of storage: nominal and usable. Nominal storage refers to the total amount of electricity that can be held. Usable storage refers to the total amount of electricity that can be used, after factoring the depth of discharge.

Power (kW): Power is measured in kilowatts (kW) and refers to the maximum amount of electricity that a battery can discharge in any one moment. The more power, the faster the battery will discharge. This is an important specification if your home uses a lot of electricity.

Cycle: A ‘cycle’ refers to a discharge and recharge of a battery. It is often used as a measurement of battery life. Most batteries have a lifespan of several thousand cycles.

Lifespan:  The ‘lifespan’ is an indicator of the time the battery is expected to last before it severely degrades. The lifespan is usually measured in years or number of cycles. The battery is still usable at the end of its lifespan, however it will only be able to hold about 60% of its original capacity.

How to get the most out of your solar battery

To maximise the potential savings of a solar storage battery, it’s important to ensure you have a suitable electricity tariff. Households with a time of use, flexible rate or even controlled load tariff stand to save the most, while single rate customers may be unable to get the same value.

Time of use and flexible rate tariffs charge different rates at different times. Electricity is usually cheapest during normal working hours and very late at night, and most expensive during peak demand periods – usually between 3pm and 9pm. Flexible rate or time of use customers with a solar battery can benefit from lower rates for most of the day, and use their stored solar power to cover peak period energy usage, rather than paying the higher peak rates. Most solar storage units can be set to automatically kick in between these hours. Alternatively, some systems are compatible with apps that let you monitor and control when and how your stored solar power is used.

A controlled load tariff can also speed-up your solar battery savings. Appliances connected to a controlled load circuit only receive electricity for a few hours per day, usually late at night. In exchange, however, the price of electricity is much lower. Customers could even connect their solar battery to a controlled load and charge their battery overnight with grid electricity for cheap. By morning, they can use their charged storage unit, rather than pay the full price for electricity.

Finally, it’s important to make sure you are with an electricity retailer that helps you get the best value on solar. Be sure to compare solar providers at Canstar Blue.

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