If you've got solar panels on your home, or you're considering getting them, then you're probably wondering if you should get a storage battery as well – and if so, which one is best?
An independent trial of solar storage batteries ran in Canberra from 2016 to 2022 to see how well they meet their performance claims over time. ITP Renewables tested batteries from Tesla, LG Chem, Alpha ESS and more, and not all of them survived.
The trial was run in three phases. Phase one began in 2016, Phase 2 in 2017, and Phase 3 in 2019. New batteries were introduced in each phase, and where practical, any older batteries still functioning were kept running. Here's a summary of the results from all three phases of the trial.
Our solar battery buying guide explains the general details of what to consider and whether a battery is likely to be cost-effective. But does a Tesla Powerwall beat an LG Chem battery? Should you go with other brands, or non-lithium types like Redflow? And do they all really meet their performance claims?
Sounds like we need a comparative test under controlled laboratory conditions! Unfortunately, while CHOICE's labs excel at product testing, a test of these batteries is far too expensive for us to undertake.
Fortunately, someone else has done the work. ITP Renewables, a renewable energy consulting and project management company, ran a battery trial in Canberra, starting in 2016 and concluding in March 2022.
With major funding grants totalling $1,290,000 from the Australian Renewable Energy Agency (ARENA), they built a test facility and tested storage batteries under an accelerated program designed to measure performance and reliability under typical Australian conditions.
- Malfunctions are all too possible with a storage battery.
- Some battery manufacturers have already exited the market, and new ones keep appearing.
- If you get a storage battery, it's best to stick with major brands to make sure you get good warranty support.
- Installation by an experienced solar battery installer is a must.
Storage battery technology is complex and still evolving, as is the industry itself. The trial has demonstrated that there's a fair chance that a battery bought today will be obsolete within a few years – or worse, it might malfunction.
Obsolescence is not a problem in itself as long as the battery keeps on working as claimed. But also, some manufacturers and distributors might not still be around to honour warranty claims – something that happened during this trial.
Apart from the possible technical issues, it's still the case that batteries don't yet make full economic sense for most households, though we expect that to change within the next decade. We recommend you do your sums carefully to understand the economics for putting one in your home.
Many people are still investing in a battery regardless of the marginal economics in order to give their home more energy security and become more independent from energy companies.
If you do go ahead and get a battery, it's important that it's installed by experienced technicians who are familiar with the individual requirements of the product. As with any solar installation, look for a CEC-accredited installer – in this case, look for one who has specific accreditation for battery installation.
You can also use our Solar Estimator tool (in partnership with SolarQuotes) to get quotes from reliable installers in your area.
Good warranty support is also essential, so we advise sticking with major brands who you can expect to still be around in 10 years.
- Several batteries failed in testing, while others have run with no significant problems.
- Only one battery from the original Phase 1 set from 2016 stayed operational all the way to the end of the trial in 2022 (Sony Fortelion).
- Some other Phase 1 models ran OK but were eventually retired from the test as their test period was over, there was no value in continuing their testing, and space was needed for newer batteries.
- Two batteries from Phase 2 ran without major problems (GNB Lithium and Pylontech), while some others had to be replaced at different times due to problems (BYD B-Box, LG Chem HV, Redflow and Tesla Powerwall 2).
- Several batteries had major failures (with either the battery itself, or essential manufacturer support) and were either removed from the test or replaced with new samples.
- A new batch of eight batteries (Phase 3) entered the trial in late 2019. Most of them ran OK through to the end of the trial, though two (SolaX and sonnen) developed faults and had to be repaired or replaced.
Overall, it's disappointing how many of the batteries failed at different stages of testing. That said, some batteries have proven to be sturdy and reliable, and support from several of the manufacturers has been good, which is encouraging.
If you're making the leap to installing a home battery, here are the solar battery models that demonstrated superior performance.
- The Sony and Pylontech battery packs demonstrated superior capacity retention – that is, their claimed capacity didn't significantly diminish over time. Other batteries introduced in Phases 2 and 3 also showed good capacity retention but were not run through as many cycles as these two.
- The Sony, Samsung, Tesla Powerwall and Powerwall 2, BYD and Pylontech had generally good reliability.
- The Samsung and BYD had consistently high efficiency. This is a measure of how much of the energy put into the battery is actually stored and able to be extracted for use again.
Individual problems and results for each battery are detailed below.
Tesla and Samsung batteries showed high reliability in the solar battery trial.
Phase 1 of the test started in 2016 with eight batteries that were available at that time, and Phase 2 added another 10 models in 2017. Phase 3 added eight more batteries which were installed in late 2019 and began testing in January 2020. Most of the batteries are lithium-ion – the most common battery chemistry available – but some other types such as lead-acid and flow batteries were included.
Each battery consists of battery cells plus a battery management system (or BMS – this is built-in hardware and software which manages the cell charge levels, voltages and so on). Most do not come with a built-in battery inverter (the device which actually controls power flowing to and from the battery).
|Battery||Trial phase||Country of origin||Chemistry||Total installed capacity (kWh)|
|CALB CA100||1||China||Lithium ion (lithium iron phosphate)||10.24|
|EcoUlt UltraFlex||1||USA||Lead acid carbon||14.8|
|GNB Sonnenschein Lead-Acid||1||Germany||Lead acid||15.84|
|Kokam Storaxe||1||Korea||Lithium ion (nickel manganese cobalt)||8.3|
|LG Chem RESU 1||1||Korea||Lithium ion (nickel manganese cobalt)||9.6|
|Samsung AIO10.8||1||Korea||Lithium ion (nickel manganese cobalt)||11.6|
|Sony Fortelion||1||Japan||Lithium ion (lithium iron phosphate)||10.24|
|Tesla Powerwall||1||USA||Lithium ion (nickel manganese cobalt)||10.24|
|Alpha ESS M48100||2||China||Lithium ion (lithium iron phosphate)||9.6|
|Ampetus Super Lithium||2||China||Lithium ion (lithium iron phosphate)||9|
|Aquion Aspen||2||USA||Aqueous hybrid ion||17.6|
|BYD B-Box||2||China||Lithium ion (lithium iron phosphate)||10.2|
|GNB Sonnenschein Lithium||2||Germany||Lithium ion (nickel manganese cobalt)||13.6|
|LG Chem RESU HV||2||Korea||Lithium ion (nickel manganese cobalt)||9.8|
|Pylontech US2000B||2||China||Lithium ion (lithium iron phosphate)||9.6|
|Redflow Zcell||2||Australia*||Zinc bromide flow||10|
|SimpliPhi PHI3.4||2||USA||Lithium ion (lithium iron phosphate)||10.2|
|Tesla Powerwall 2||2||USA||Lithium ion (nickel manganese cobalt)||13.5|
|BYD B-Box HVM||3||China||Lithium ion (lithium iron phosphate)||11.04|
|DCS PV 10.0||3||Australia/ China/ Japan||Lithium ion (lithium iron phosphate)||10|
|FIMER REACT 2||3||Italy/ Japan||Lithium ion (nickel manganese cobalt)||8|
|FZSoNick||3||Switzerland||Sodium nickel chloride||9.6|
|PowerPlus Energy LiFe Premium||3||Australia||Lithium ion (lithium iron phosphate)||9.9|
|SolaX Triple Power||3||China||Lithium ion (nickel manganese cobalt)||12.6|
|sonnenBatterie||3||Germany/ Australia||Lithium ion (lithium iron phosphate)||10|
|Zenaji Aeon||3||Australia/ China||Lithium ion (lithium titanate)||9.6|
* Designed and assembled in Australia; battery manufactured in Thailand.
We've listed the batteries below in alphabetical order. Typical problems encountered include:
- operational failures such as the battery shutting down unexpectedly or unexpectedly reducing in performance
- lack of manufacturer support for technical issues
- accelerated capacity fade (the capacity of the battery is how much energy it can store – it's expected to decline in an orderly fashion over several years, but for some models their capacity faded faster than it should)
- poor performance during summer temperature tests (batteries don't generally like extreme temperatures, but these models should be expected to cope with a wide range of climates).
ITP Renewables used SMA inverters in their test of solar battery storage.
ITP Renewables built a climate-controlled fire-proof test room with the batteries installed inside it and connected to inverter units on the outside. Power was supplied from the mains grid. The aim was to cycle (charge and discharge) each battery three times each day, which over three years in the trial is roughly the equivalent of nine years of use in a typical setting.
This is more cycles per day than the batteries would experience in normal use, but the program wasn't designed to stress the batteries unnecessarily. That said, the accelerated test program may have affected some batteries more than others.
Read the full reports for each stage of the trial.
Possibly the major lesson for CHOICE is that running a battery test is just as challenging and fraught with unexpected outcomes as we thought, and we're very glad ITP did it instead.
Faulty and discontinued products
The battery trial encountered a number of technical challenges, including several batteries developing faults and having to be removed or replaced. Several models are no longer available, as companies collapsed or withdrew from the battery market, or the products were superseded by new versions. This illustrates how relatively new this technology and industry still is. The industry has already matured significantly since the battery test began and we expect this will continue.
Integrating batteries with suitable inverters also proved problematic in many cases, in particular with the battery-inverter communications interface.
The trial has also demonstrated how difficult it is to devise a single test regime that covers several different battery chemistries and specifications, as they each have different performance limitations. It's likely that the test regime worked better for lithium-ion batteries than for lead-acid, for example.
Over the course of this project, the Battery Test Centre provided a very valuable amount of data and insight regarding the performance of a wide range of storage batteries.
As well as the lessons learned for consumers, noted above, ITP Renewables made some observations about the storage battery market.
- The company noted a trend towards integrated battery and inverter systems, or battery/inverter compatibility only between models from the same manufacturer. This removes some of the problems that might otherwise arise from mismatched inverters and batteries, but also removes some flexibility for installation.
- It also noted a trend towards high-voltage inverters and battery packs, which are generally simpler to install, more efficient and potentially less expensive.
ITP believes (and we agree) that the trial has overall been a success, raising interest in storage batteries with consumers and providing them with valuable data, and helping to increase accountability from battery manufacturers on the performance and support for their products.
With the trial complete, ITP is investigating options to decommission or dispose of the tested batteries and the testing facility itself, with a preference to finding a home for the products and equipment that allows ongoing knowledge-sharing, such as electrical training programs.
Our thanks to ITP Renewables for assisting us in producing this summary.
Stock images: Getty, unless otherwise stated.