What Makes A Great Battery Warranty?

Solar adoption in the US continues to rise even in the face of less favorable net energy metering (net metering, NEM) policies. With decreasing NEM rates the attachment rate of batteries to solar projects is also increasing throughout the country. Couple that with an aging electric grid and increasingly severe weather patterns and you’ll start to see battery storage solutions pop up as often as solar. 

Whether you’re looking into a storage solution, just installed a battery, or already have one, it’s important to understand the warranty; what’s covered, what’s excluded, where are your limitations, and how to select a good battery.  

Battery Types

For residential uses of critical loads or whole home backup there are many types of batteries but in practice mainly two are used:

Lithium-Ion (Nickel-Manganese-Cobalt, NMC)
The most commonly used battery type because of their high-efficiency, long lifespan, and size. 

Warranty Range: 10-15 years 

Common Brands: Tesla, LG, SolarEdge, Panasonic

Lithium Iron Phosphate (LiFePO₄) Batteries
A subtype of lithium-ion batteries, LiFePO4 batteries are gaining popularity due to their safety and stability.

Warranty Range: 10-15 years 

Common Brands: Tesla, Enphase, FranklinWh, Fortress Power

Other types are available but are more often used for off-grid or in the DIY community. 

Lead-Acid
Lead-Acid batteries have been used for decades and known for reliability and a lower upfront cost. Most common for off-grid solar energy systems. 

Warranty Range: 3-5 years

Nickel-Based
Nickel-based batteries, such as nickel-cadmium (NiCd) and nickel-metal hydride (NiMH), are less common but still used in certain applications because of their performance in extreme temperatures. 

Warranty Range: 5-10 years

How Long Are Manufacturer Warranties?

Unlike solar panels or inverters, which normally carry 25-year warranties, solar battery warranties are often far shorter. The industry standard for batteries is 10-12 years; the timeframe is influenced by the battery’s chemistry and rarely will manufacturers offer a warranty for longer.

It’s important to note that some battery warranties also carry cycle limits. A cycle is defined as a full charge and discharge of the battery’s energy. Much like a car warranty of 10 years or 50,000 miles, if you hit the cycle limit before the battery hits the 10 year mark your warranty period will be concluded.

Some manufacturers interchangeably call a cycle limit a “throughput warranty”. If a manufacturer provides a throughput warranty of 30MWh – or 30,000 kWh – the warranty period ends once the battery charges and discharges that amount. For example – a battery with a 13.5 kWh capacity would have to cycle 2,223 times to meet a 30,000 kWh throughput warranty. At one cycle per day the throughput warranty would be met in just over 6 years.

Make sure to consult a battery’s limited warranty documentation. Some warranties claim to give “unlimited cycles” but put a cycle limit on “if operated by a third party” or if the battery is used in non-standard ways.

Manufacturer Examples:

SolarEdge Warranty:

Tesla Powerwall 3 Warranty:

FranklinWh Warranty:

What is Covered By the Warranty?

In most cases, manufacturer warranties will cover the replacement of the faulty equipment. Industry standard for battery warranties is to guarantee 70% capacity retention at the end of the 10-12 year period. So if your battery started with 10 kWh usable capacity, by the end of the warranty period the battery may only have a usable capacity of 7 kWh. 

If there were a fault in the equipment that caused a failure or the capacity were to fall below 70% during the 10 year period, the battery would be eligible for replacement. 

Some batteries may linearly degrade, others may stay at a certain capacity for a few years then experience a larger drop. Unsurprisingly, manufacturers don’t typically publish that data. Consider your cell phone battery, if you leave it dead, overcharge, or drain the battery too quickly for long enough, the capacity seems to disappear overnight. The same applies to a home battery.

What is Excluded?

• Labor to replace or service faulty parts
• Damage or malfunction from improper installation
• Superficial marks (dents or scratches) that occur from normal use
• Environmental Damage including: floods, extreme temperatures, lightning 
• Theft

Replacement of equipment and shipping are generally where battery warranties end. Labor to replace or service those faulty parts is not often covered by the manufacturer and can end up falling to homeowners or installers, depending on the contract. 

Important to note, many manufactures will not honor a warranty if the product is not connected to a monitoring service via the internet. 

Limitations and Choosing the Best Battery

When looking at a battery for your solar system it’s important to consider all aspects of the battery and your use case. We’ve previously compared a few popular market options which you can read here.

On top of considering your total capacity needs, also consider your location when choosing a battery. Batteries will often have altitude limitations, limitations on their exposure to salt water, or limitations of temperature.

Batteries are not rated for prolonged exposure to extreme temperatures. The Tesla Powerwall 3 for example is rated for -4℉ to 122℉. If you live in a northern region that experiences extreme cold, having your battery outside could void the warranty. Putting the battery inside may not be possible due to local codes or space requirements. 

When choosing a battery for your home, you should be honest with yourself about how you intend to use the battery. Most common uses include:

• Self Consumption: charging the battery from excess solar power and discharging when your home requires more energy than the solar panels are producing.
• Rate Arbitrage: Where allowed by the utility, this involves charging when rates are low (or you have excess solar power) and discharging when rates are high (or into the home to avoid pulling grid power during high rates). Some utility companies do not allow you to discharge into the grid.
• Emergency Backup: Maintaining a portion or all of the battery capacity for power outages. 

Your answer to the above question will help guide you to the type of battery you’re looking for and how many of them you may want. 

Groundbreaking Long Term Battery Protection

What should you do with a battery after the 10-12 year warranty period? At 70% capacity retention, there’s still a lot of useful life left in the battery, but capacity will continue to decline. Much like your cell phone battery, eventually it won’t hold much of a charge and will need to be replaced, usually costing over $10,000.

Solar Insure offers an unmatched protection for battery storage. Solar Insure’s SI-30 Total warranty provides 30 years of solar system and battery coverage and is designed to maintain homeowner peace of mind throughout the lifetime of the battery, even after the manufacturer warranty period has expired. 

With SI-30 Total, Solar Insure provides one replacement battery if the capacity falls below 50% in years 11-30, protecting you from inevitable capacity reductions. Having Solar Insure also protects battery owners from costly labor charges that the manufacturers don’t cover. 

Tripling the warranty period and ensuring your investment pays dividends long term is only achievable through the unmatched protection from Solar Insure.

Learn more about Solar Insure for providers and homeowners.