What you need to know about solar battery warranties

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Solar batteries store extra power generated by solar panels for later use. They include warranties that describe the battery's anticipated life and performance. However, it's also critical to realise that batteries can deteriorate over time and that their useful lives may exceed their guarantee periods. This is why the question: "How do solar battery warranties work?" is so common. 

Given that manufacturer, warranties might differ significantly from one another. It is crucial to read them and comprehend what is thoroughly and is not covered. Others may only cover the battery if it retains a specific percentage of its original capacity. Some warranties may only cover the battery for several years or cycles.

What can you tell me about solar battery warranties?

Solar battery warranties are sometimes not as explicit as straightforward products, like a washing machine or a fridge.

With such household equipment, it either works or doesn’t work. If it doesn’t work the failure is within the warranty period, and there was no abuse – you got a valid claim.

With solar home storage batteries, it’s not always that simple. Solar batteries have a derate factor and degrade over time. So that means the battery will retain a little bit less of the original storage capacity every year.

Hopefully, there will be a point after a decade or more when you feel that the battery is not doing the job properly anymore. It discharges too quickly, does not hold enough charge, or stops working.

This is when the battery has reached the end of its useful life. Usually, the valuable life period should be more extended than the warranted life. Generally, the solar battery only retains 60 to 70% of its original capacity.

Many of us have experienced this situation with our phones or laptops. After some years, the solar battery life of the item gets shorter and shorter. This is because the battery is degrading.

Most good solar batteries in Australia and NZ last at least 10 years because lithium battery technology is still new. However, we must see if 12, 15, or even 20 years is a possible lifespan in future years.

How do solar battery warranties work?

Modern solar batteries from brands like Tesla, Panasonic, BYD, or Sungrow use lithium-ion technology. Lithium-ion has a higher energy density and lower discharge rate. This means more energy can be stored in smaller-sized batteries, and more energy can be discharged.

In residential homes, it can be hard to find enough space for a large lead acid battery bank. The photo below shows how this can be useful. In addition, lead-acid batteries are cheaper than lithium-ion batteries. However, some models need more maintenance and significantly lower cycle life.

commercial solar batteries
Lead-acid batteries are cheaper, however, requiring larger energy storage space and a lower life cycle

As this industry is still emerging, battery manufacturers have developed different warranty conditions and fine print. A solar battery should generally be considered to have a limited lifespan, like an engine designed for 200,000 km. After 200,000 km, it is not likely the equipment will last much longer.

Unfortunately, solar battery warranties have not been standardised. Therefore different manufacturers express warranties in different ways, which can make understanding battery warranties a little confusing.

Generally, a solar battery warranty can consider up to four criteria. These four can also be mixed, and maybe only two of the four we mention apply to your particular model. The information below will assist you in understanding the warranty jargon in the warranty documents.

Warranty for years

Firstly the warranty specifies a period. So, for example, this solar battery system will perform under normal conditions, e.g. not stored over 50 degrees Celsius, for 10 years.

Warranty in cycles

Secondly, some batteries give a cycle warranty; for example, this battery can handle 5000 cycles. A cycle is a complete charge and discharge of the solar battery. So if you have a fully charged 10 kWh battery and in the morning you discharge 3 kWh, your solar puts 3 kWh back into the battery during the day.

The next day you now discharge 7 kWh and recharge 7 kWh. You have now released 10 kWh and charged 10 kWh – so that’s one cycle. Even though it took two days and was undertaken in “4 transactions – 2x charging and 2x discharging”

Furthermore, let’s say you put one full charge and one full discharge on average a day, being one cycle, and then you do these, let’s say, 350 times a year. So that means after 10 years, you will have had 3,500 cycles with this battery. So with a warranty of 5000 cycles, the battery will be warranted for just over 14 years.

Solar battery warranty in throughput energy

Thirdly there is the throughput of energy warranty. This means “this solar battery can handle that many kWhs of throughput”.

Whereby the battery has a given number of kWh being charged and discharged over a certain number of years. This option would let the purchase accurately calculate the financial benefits of a solar battery.

Battery warranty for % of capacity after a certain period

In addition to government incentives, homeowners exploring solar energy and battery solutions also have the option to retain a portion of the initial kilowatt-hour (kWh) capacity after a specified number of years. This feature lets homeowners change their energy systems over time without needing to replace everything.

Retaining a portion of the initial kWh capacity ensures long-term benefits, contributing to cost-effectiveness. This option adds an extra layer of value to the investment in solar and battery technology.

Tesla powerwall installed on wall
The details of battery warranties have changed over the years

Let’s standardise solar battery warranties in Australia and NZ

Hopefully, solar battery regulations and datasheets, including warranty considerations, will be homogenised and standardised in a few years. This will allow the purchaser to compare apples with apples.

So please have a read of your solar battery warranty. Hopefully, our information can assist you in understanding the fine print. We recommend you pay close attention to the warranty conditions for battery replacement—especially the exclusion clauses.

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