Your guide to batteries

As more WA homeowners and businesses generate their own solar power, batteries and storage are fast becoming part of the energy lexicon.

But which batteries do what?

Here’s the breakdown of the different types of batteries you might come across and what they mean for you.

How batteries are measured

The first thing to understand is that batteries are measured in two ways:

• by their maximum power output (kW)
• the amount of energy it can store (kWh)

1. In-home batteries

• These are the “next step/ follow-on” from household solar panel installs and used to store surplus solar power for the home
• Sized between 4kWh to 16kWh, enough to supply most households
• Lithium-ion is the most common battery cell chemistry used, but others available

An in-home battery is bought, owned, maintained and managed by the homeowner. They store excess solar power generated by rooftop panels and can feed power back into the home when needed, like after the sun goes down.

The battery is connected to the grid as part of an inverter energy system, it is charged by your solar panels and may also be charged from the grid. Most systems are configured to never charge from the grid and only charge form the solar panels. 

This means you need to be generating enough solar power (surplus to your day time usage) to charge up the battery for use when needed.

The storage capacity of in-home batteries ranges from 4kWh up to 16kWh.

There are different types of in-home batteries available in Australia. This means there are different battery chemistries and lithium-ion batteries are by far the most common. However, there are also lead acid, vanadium flow and sodium nickel chloride batteries.

Even though in-home battery units are not large, they hold significant amounts of energy. They need to be installed properly in accordance with the national battery standards which stipulate the strict requirements for correct and safe installation on a property. The cost of an in-home battery is on average between $7,000 to $13,000 and there are ongoing servicing and maintenance costs that need to be considered.

Battery prices have been relatively stable in recent years.

Solar Choice regularly crunches the numbers to help consumers understand the  for in-home batteries. 

Batteries can be a viable option for consumers, but at current prices, customers are required to transition onto a time-of-use tariff and get very high utilisation of the battery. However this is not possible for many due to daily fluctuations in usage. If you’re considering getting your own in-home battery, there are 8 things you should consider first.

Home batteries can also help support the grid. Virtual Power Plant (VPP) trials are underway which explore how the battery can be used to benefit both the customers and the grid (without VPP functionality, potential benefits are likely to be lost).

2. Community batteries

• Stores excess solar power from homes within an area/ network
• Connected to the grid with residents able to ‘virtually’ store their surplus power
• Lithium-ion batteries sized 105 kW/420 kWh up to 3MW/12MWh, though could be bigger.

This is an exciting new development in the realm of batteries that makes more financial sense for many customers than having their own in-home battery.

Community batteries consist of a physical utility-sized (105kW to 116kW) battery installed in a suitable location. There are a number of factors that determine the location of a community battery, including the amount of rooftop solar in a particular area.

Community batteries are currently also lithium-ion batteries, though bigger than an in-home battery. They are connected to the grid and store excess solar energy from households in that area. An added benefit is they also help to smooth the flow of power on the local network grid.

Community batteries also unlock the potential for customers to virtually store their excess solar power in the battery and draw it back out again (to a limit) when needed. There are currently three trials with this virtual storage model, known as a PowerBank, and they are managed in partnership with Synergy.

Benefits include:

• Economies of scale regarding the battery cost
• Place in specific locations for network need and has a greater community benefit
• Shared capacity servicing multiple customers

Another battery you may hear about are those used in stand-alone power systems (SPS)

3. Stand-alone power systems (SPS)

• Used on rural properties across WA and not connected to the grid
• Consist of solar panels, battery and a diesel generator
• The battery is part of a stand-alone system which stores energy generated from solar panels
• Lithium-ion batteries are typically sized between 20kWh and 50kWh

In regional WA, some rural properties have often experienced poor power reliability due to aged assets. As part of our SPS program, these properties have been converted to stand-alone power systems as a result of their network requiring replacement which has improved power supply to these properties.

These SPS units consist of solar panels, a lithium-ion battery and in some cases, a back-up generator. Sized to meet the specific energy needs of the property, such as powering up homes or shearing sheds, the SPS work by generating and storing localised power; similar to a mini-microgrid system.

4. Microgrid batteries

• Bespoke utility-scale lithium-ion batteries
• Sized from 1MW to 5MW in WA, but can be bigger
• Part of a system that can power an entire area independently for several hours at a time

Microgrid batteries are utility-sized batteries – as in, they can power a whole town temporarily while any fault on the main line is fixed. Just like the other types of batteries currently used in WA, they are lithium-ion batteries. However unlike other batteries, they improve reliability by helping avoid outages.

These batteries can be connected to the grid but can also be used in combination with other power sources (solar, wind or diesel generators) to create an isolated island of power, forming a microgrid.

The microgrid batteries are large and bespoke, designed to meet the needs of that islanded network. For example, the battery in the Perenjori microgrid has a capacity of 1MWh while the one being installed in Kalbarri has 2MWh. In comparison, the largest in-home battery on the market at this point can store 16kWh (around 1% of 2MWh). 

More information