Solar battery storage buying guide
A guide to evaluating and buying a solar battery.
This solar battery storage guide evaluates the feasibility of solar batteries and tells you how to buy a good one. It is suitable if you already have solar or if you are looking at a new panel and battery system.
Solar battery storage is still a new technology; prices, on the whole, remain high, and there are reported cases of reliability issues. Payback periods for hybrid systems (panels and battery) typically stretch out beyond ten years, at which point, you will need to replace your battery.
Solar battery storage does not compare favourably to solar panels when it comes to payback results.
Solar battery prices
Solar batteries are not cheap. Whereas a 5kW solar panel system costs between $5,500 – $8,000, expect to pay between $16,000 – $22,000 for a 6.6kW system with a 10kWh battery. Like solar panel prices, battery prices vary depending on the brand. Unlike solar panels, there is no Australian rebate available for batteries. There are, however, a handful of state government schemes that may reduce the cost of a battery for you.
The table below shows prices for different size batteries:
|4.8kWh Battery:||$5,000 – $8,000|
|10kWh Battery:||$10,000 – $12,000|
|13.5kWh Battery:||$13,500 – $16,000|
Cost if you already own panels
If you already own a solar panel system, the payback on adding a battery is typically longer than that for consumers that buy a new hybrid system. You will likely need a solar system size of at least 5kW to power your battery and, you may need to buy a hybrid inverter for your new battery.
|4.8kWh Battery with 5kW panels:||$11,000 – $14,000|
|10kWh Battery with 6.6kW panels:||$18,000 – $23,000|
|13.5kWh Battery with 6.6kW panels:||$20,000 – $25,000|
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Payback periods and savings
The best way to assess the viability of solar storage is to use our solar panel and battery calculator. The calculator displays results for both solar panels and hybrid systems, allowing you to compare the payback periods and savings. If you already own panels, use our battery calculator.
Solar panels vs hybrid systems
For this example, we will use a household in Melbourne. Although Melbourne residents receive a smaller solar panel rebate than Sydney and Brisbane residents, it is still possible to payback a solar panel system within 5-6 years. We compare a 6.6kW panel system with a hybrid system consisting of 6.6kW panels and a 10kWh battery:
- Payback for 6.6kW solar panel system: 6 years
- Payback for 6.6kW hybrid system: 10 years
- Savings: Hybrid system $484 / year greater
Payback period vs warranty
If we consider a 6.6kW system with a 10kWh battery, while the savings are higher, the payback period jumps out to 10 years. Solar batteries typically only come with a 10-year warranty. You will likely need to replace it well before the system pays for itself.
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Solar battery rebates
If you buy a panel and battery system, you will receive a rebate from the Australian government on your solar panels, but not on your battery. However, you may be able to access a solar storage rebate from your state government.
South Australia battery rebate
If you live in South Australia, you can receive a rebate of $500 for every kWh of battery storage that you install. The South Australian rebate reduces the price of a 10kWh battery by $5,000.
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Victorian battery rebate
Solar Victoria’s home solar scheme provides up to a $4,838 battery rebate for existing panel owners. The Victorian rebate is only available if you live in one of the designated ‘growth’ suburbs on Melbourne’s outer metropolitan ring.
Australian Capital Territory rebate
The Australian Capital Territory government provides up to a $4,000 rebate on the purchase of new battery storage systems. The rebate is only available through select retailers.
If you live in New South Wales, Western Australia, Tasmania, Northern Territory or Queensland, there are currently no battery rebates available.
Reliability and longevity
If you buy good solar panels, you can expect them to last for 25 years. The best solar panels will even operate at 90% of their rated output after 25 years. It is a different story for batteries. Solar battery storage technology is developing rapidly; how do we know that batteries will last their as long as their 10-year warranty suggests?
Results from ongoing battery trial
Canberra consulting firm ITP Renewables is conducting an ongoing trial of over 15 different solar batteries. While still in its formative stages, there have been many reliability issues with various batteries. In fairness, many of these issues have been with the first phase of batteries from each of the manufacturers. However, the results highlight the teething problems associated with new technology. If you do decide to go ahead and add battery storage to your system, be aware you may face some reliability issues.
Our verdict: Buy or wait?
All things being equal, we would recommend you buy solar panels and delay your battery storage purchase. The increase in solar feed-in tariffs in recent years has diminished the viability of battery storage somewhat. In short, the bigger the gap between your feed-in tariff and the price you pay for electricity at night, the more feasible a battery is. For many consumers, this price differential is between 15 – 20c per kWh. If you have a 10kWh battery with 9.4kWh of usable capacity, you can save an additional $1.40 – $1.80 per day. At best, you will save an extra $700 per year, at the end of 10 years savings may increase to $8,000 but this is still well below the average cost of $12,500 to install the battery in the first place.
Battery ready system
Many consumers choose to buy a battery ready system with a hybrid inverter in preparation for a solar battery. While it is sensible to delay the purchase of a battery, you need to consider when you plan to install it. If you do not buy a solar storage solution within three years, technology may render your hybrid inverter redundant. It also costs a little more to buy a battery ready system.
Features of battery storage
Solar battery storage can add several features to your hybrid system that are not possible with just solar panels. Features include:
- Backup power
- Selling kWh units at high market prices
- Use your solar power at night
It is possible to have backup power functionality with a hybrid system. Power backup means that your system can run in the event of a blackout. The Tesla Powerwall 2 comes with built-in backup power functionality, but for most batteries, a change in configuration is required. Backup power can increase the cost of solar battery storage by up to $1,000.
Take advantage of high market prices
It is possible to sell the power stored in your battery back to the grid when prices are very high. Reposit is the leader in this technology, and their device allows you to sell your power during times of peak demand. Again, this feature will add to the cost of your solar battery storage solution.
Use your solar power at night
The genius of battery storage technology is that it allows you to store the solar power that you generate during daylight hours for use at night.
How does battery storage work?
Solar panels work by converting sunlight into electricity when the sun is shining. If you use electricity at that time, your solar will power it, if not, you export it back to the grid. Battery storage works by storing the power from your panels that you do not use. You can then use the stored power at a later time when the sun is not shining.
As with solar panel installation, who you select to install your battery is vital to the safety and ongoing performance of your system. You need to ensure that the Clean Energy Council certifies the installer for solar panel and battery installations. You need to pay particular attention to the battery warranty, and who is responsible if your system does not perform as it should.
Quotes from the best installer companies
We can provide you with quotes from installer companies that meet all of our strict vetting criteria. Compare your quotes with confidence knowing that they are from three of the best companies that service your area.