Which Solar Battery Lasts The Longest?
One of the most important features of a battery is how long it lasts. After all, there is a reason that Energizer has been advertising that their batteries “keep going, and going, and going” for the better part of 25 years…
But when it comes to investing in home battery storage, the stakes are much higher than picking a Triple-A battery to power your TV remote.
With tens of thousands of dollars on the line and dozens of solar battery brands to choose from, it’s worth taking a minute to consider which solar battery lasts the longest. In this article, we’ll explore which battery type lasts the longest and the best solar batteries to buy if longevity is your primary concern.
What is the longest-lasting solar battery type?
The lithium-ion batteries that dominate today’s residential energy storage market have a usable life (70% capacity or more) of 10-15 years, which is roughly double the lifespan of the lead-acid batteries used in the past. However, the lifespan of a lithium-ion battery also depends on its chemistry and how you use it.
There are two lithium-ion battery chemistries that are especially widespread in today’s market:
- Lithium iron phosphate (LFP) is used in Franklin Homepower, sonnenCore+, Panasonic EverVolt, Enphase IQ, and SunPower SunVault batteries
- Lithium nickel manganese cobalt oxide (NMC) is used in LG ESS Home8, LG RESU Prime, Generac PWRcell, and Tesla Powerwall 2 batteries
In general, LFP batteries tend to last longer than NMC because they are more resistant to high temperatures that degrade battery life. However, the lifespan of a battery also depends on how you use it.
According to a 2020 study by the National Renewable Energy Laboratory (NREL):
- LFP batteries last longer in self-consumption mode, where the battery is charged with solar energy during the day and discharged to power household systems at night to avoid interaction with the grid
- NMC batteries last longer in backup mode, in which the battery maintains a high state of charge and is only discharged during grid outages
So, if you plan on charging and discharging your battery every day, an LFP will likely last longer. If you only plan on using your battery for backup power during grid outages, an NMC battery will likely last longer.
Next, we’ll look at some of the longest-lasting battery models for each chemistry type.
Longest-lasting solar battery models of 2023
Alright, so we’ve narrowed the longest-lasting solar batteries into two lithium-ion chemistries: LFP and NMC. Now let’s take a step further and look at some of the longest-lasting battery models for each chemistry based on the warranty terms offered by each manufacturer.
Battery warranties guarantee that a certain level of usable storage capacity will remain after a set number of years or usage, whichever comes first. Usage is measured in two ways:
- Cycles: The number of times a battery charges and discharges
- Energy throughput: The total amount of energy the battery charges and discharges
In 2023, a “standard” solar battery warranty is for 70% of nameplate capacity after 10 years and 3,000 to 4,000 cycles. The batteries on the lists below carry warranties that go above and beyond this standard in some way.
Longest-lasting LFP battery warranties
Lithium iron phosphate (LFP) has emerged as the longest-lasting battery type on the market, as indicated by 12 and even 15-year warranties (as opposed to the standard 10 years).
Some of the longest-lasting LFP batteries are listed in the table below.
|Brand/Model||Usable capacity||Warranty terms|
|Franklin Home Power||13.6 kWh||70% capacity after 12 years or 43MWh throughput|
|sonnenCore+||8.6 kWh||70% capacity after 10 years or 10,000 cycles|
|Panasonic Evervolt||9 / 13.5 / 18 kWh||70% capacity after 12 years|
|Enphase IQ 5P||5 kWh||60% capacity after 15 years or 6,000 cycles|
|SunPower SunVault||13 / 19.5 kWh||70% capacity after 10 years (unlimited cycles)*|
*Unlimited cycle warranty may not be valid for “homeowners who charge over 5MWh from sources other than PV”
A few LFP battery warranties that stand out:
- Enphase is among the first manufacturers to offer a 15-year warranty
- SunPower is among the first manufacturers to offer an “unlimited cycle” warranty, but there is a clause that limits charging from the grid
Now, let’s see how the top LFP battery warranties compare to the top NMC battery warranties.
Longest-lasting NMC battery warranties
In general, the warranties for NMC batteries are shorter and cover less usage than the warranties for LFP batteries. The table below shows the warranty terms for the best NMC batteries on the market in 2023.
|Brand/Model||Usable capacity||Warranty terms|
|LG ESS Home8||14.4 kWh||70% capacity after 10 years or 59.8 MWh throughput|
|LG RESU Prime||9.6 kWh||70% capacity after 10 years or 32 MWh throughput|
|Generac PWRcell||9 kWh (3 x 3 kWh modules)||70% capacity after 10 years or 7.65 MWh per module|
|Tesla Powerwall 2||13.5 kWh||70% capacity after 10 years (unlimited cycles)*|
A few things that stand out:
- We were not able to find an NMC battery warranty length beyond 10 years
- Tesla offers an “unlimited cycle” warranty on the Powerwall 2, however, it only applies to charging the battery with solar energy
Choosing the right solar battery
To recap, based on the manufacturer’s warranties (which tend to be conservative) you can count on today’s lithium-ion solar batteries to last at least 10 years – and perhaps up to 15.
However, your battery life is influenced by:
- Its chemistry (LFP vs NMC)
- How you use it (self-consumption vs backup)
- Its storage conditions (hot batteries = shorter lifespan)