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Written byShaun McGowan
Storage batteries are increasingly popular with new solar installations.
Fuelled by the continued success of brands like Tesla and Sonnen, the further adoption of electric vehicles around the world, and an increased awareness of green energy benefits, it’s likely that every installation will have a solar battery within the next 10 years.
Without a battery, any excess solar energy your panels produce is diverted back to the grid. A battery captures any unused solar power generated during the day for later use at night and on low-sunlight days.
A well-planned and constructed solar panel array and battery can run your home substantially on solar power while reducing the payback period of the components considerably.
Using electricity from your battery can also be cheaper than using electricity from the grid, depending on the time of day and electricity tariffs in your area.
How much energy the battery can store, usually measured in kilowatt-hours (kWh). The nominal capacity is the total amount of energy the battery can hold; the usable capacity is how much of that can actually be used, after the depth of discharge is factored in.
Expressed as a percentage, this is the amount of energy that can be safely used without accelerating battery degradation.
Most battery types need to hold some charge at all times to avoid damage. Lithium batteries can be safely discharged to about 80–90% of their nominal capacity.
How much power (in kilowatts) the battery can deliver. The maximum/peak power is the most that the battery can deliver at any given moment, but this burst of power can usually only be sustained for short periods.
For every kWh of charge put in, how much the battery will actually store and put out again. There's always some loss, but a lithium battery should usually be more than 90% efficient.
Also called the cycle life, this is how many cycles of charge and discharge the battery can perform before it's considered to reach the end of its life.
The expected life of the battery (and its warranty) can be rated in cycles or years. The lifespan should also state the expected level of capacity at the end of life; for lithium batteries, this will usually be about 60–80% of the original capacity.
Batteries are sensitive to temperature and need to operate within a certain range. They can degrade or shut down in very hot or cold environments.
The amount of storage you need to buy, in kWh, depends on your nighttime energy use.
Here’s an example of your average Aussie home.
Costs vary significantly for solar batteries, but generally, the higher the battery capacity, the more you can expect to pay:
The lower-end prices tend to be for a battery pack only, while higher-end prices include battery systems with a built-in battery inverter and other integrated components as well.
A highly efficient system with a correctly installed and configured solar battery can reduce your grid use by up to 95%, eliminating electricity and feed-in tariff changes.
If you’re considering a solar battery, then your main consideration will be the cost and payback period of the battery - something you may not experience if you’re not maximising your use of feed-in tariffs.
If you choose to install a battery, every kWh diverted to charging your battery will be a potential saving you’ve missed from forgoing the feed-in tariff.
A solar battery provides energy security above all else, and some households may find the right balance between energy storage and sending energy back to the grid.
Batteries also provide a form of insurance against the risk of electricity prices going up and feed-in-tariffs going down.
Want to save on solar? These are current rebate or special loan schemes available in some states and territories of Australia:
Rebate schemes change from time to time, so it's worth checking the Federal Government energy website to see what's available in your area.
There are also various Virtual Power Plant (VPP) programs in most states which can help reduce the cost of a battery.
By joining a VPP program:
Most solar batteries are designed to operate at high efficiency for a number of decades, provided they’re taken care of and not subjected to severe conditions.
However, Australia is home to a harsh and unforgiving climate in some areas, and there simply isn’t enough data to fully understand the lifespan of batteries in the Australian climate.
Reputable brands are always the more secure option when choosing a battery; cheaper brands have sometimes gone out of business and been unable to fulfil requests for replacements under warranty.
You can learn more about each of the components of a complete residential solar energy system in the guides below.
Before you go ahead with installing solar to reduce your energy bills, it’s worth taking a look at the available solar rebates in your state.
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Shaun is the founder of Money.com.au and is determined to help people pay as little as possible for financial products. Through education and building world class technology. Previously Shaun co-founded CarLoans.com.au and Lend.