While lithium-ion solar batteries are more popular than ever, they're not all built the same. And we’re not just talking about differences between brands - what the batteries are actually made of can make a big difference in how they perform. 

There are two popular types of lithium-ion batteries for solar storage: lithium iron phosphate (LFP) and nickel manganese cobalt (NMC). LFP has quickly become the industry standard for new lithium-ion batteries, as it can better withstand high temperatures and doesn’t contain toxic metals, making it safer than NMC. NMC is still used by popular brands like Tesla and LG Chem and has powered homes across the country for years. 

Both are solid options for homeowners who want to store the energy their solar systems produce. But which one is right for you? 

What is a lithium-ion battery, and how does it work? 

Before we can get into the good stuff, we need to cover the basics of how lithium-ion batteries work. There are four main components of a lithium battery that you need to know about: 

• The electrolyte, which contains the lithium ions
• The separator, that allows lithium ions to flow through the battery while preventing the movement of electrons
• The cathode, where lithium ions are stored until the battery is charged
• The anode, where lithium ions are stored until the battery discharges

Lithium ions move from the cathode to the anode when being charged, and move back again when the battery is discharged. 

When the battery is being charged, the lithium ions flow through the electrolyte from the cathode to the anode. Then when the battery is being used, the ions flow from the anode, back to the cathode. This creates an electrical current that moves from the current collectors to the electrical devices in your home!

What is an NMC battery? 

An NMC battery is a type of lithium ion battery. NMC batteries have a cathode made of a combination of nickel, manganese, and cobalt. You’ve probably used NMC batteries more often than you realize - they power smartphones, laptops, and electric vehicles. They’re also one of the most popular options for solar storage.  

NMC batteries overtook lead acid batteries as the most popular choice for solar storage because they last longer, store more energy, and require less maintenance. In fact, many of the most popular solar batteries on the market today are NMC batteries. 

*Estimated price before installation costs, incentives, and the federal tax credit

What is an LFP battery?

LFP batteries have a lithium iron phosphate cathode (LiFePO4). The iron and phosphate used to make the cathode are more abundant and less expensive than some of the materials used in NMC batteries - mainly cobalt. Plus, the materials in LFP batteries are far less toxic than those in NMC, making them easier to recycle at the end of their life. 

Recently, more and more companies have been manufacturing LFP batteries as opposed to NMC for home energy storage, mostly because LFP batteries are safer and more stable (we’ll get more into that in a minute). Some popular LFP home batteries include: 

*Estimated price before installation costs, incentives, and the federal tax credit

NMC vs LFP 

There are a few key things to consider when you’re shopping for a solar battery, including the battery’s performance, its lifespan, its safety, the cost, and its overall value. 

Let’s take a look at how NMC and LFP batteries stack up against one another.

Performance 

Winner: Tie

In general, the overall performance of NMC and LFP batteries are pretty much the same. You can find both types in a variety of sizes, from as little as 3 kWh to over 20 kWh. Most homeowners only need around 10 kWh of storage, which you are sure to find from both types. 

With that said, there are some slight differences between the two. LFPs are slightly more efficient and can operate a little better when the state of charge is low compared to NMCs, but NMCs can better withstand colder temperatures. However, you probably won’t have to worry about this if your battery is installed inside, or if your area doesn’t experience significant temperature extremes. 

NMC batteries also have a higher energy density, meaning that their physical size will be smaller than LFP batteries of the same capacity. This isn’t usually a concern for homeowners, but if you do have limited space then you may need to consider an NMC battery. 

Lifespan 

Winner: LFP 

As you use a battery, it loses some of its ability to hold a charge. Think of your cell phone - you probably need to charge it more frequently now than you did when you first got it. The same thing happens to solar batteries. 

Degradation happens more slowly with LFP batteries, so they’re able to store and release more electricity than NMC batteries over time. Keep in mind that the quality of the battery will also play a role in how long it will last, so you might want to read through the product warranty before you make a decision. 

A cheap, poorly made LFP battery might not outlast a high-quality NMC battery. But, you’re probably not going to come across many shoddy batteries, so long as you choose a reputable installer. 

Safety 

Winner: LFP 

One of the biggest benefits of choosing an LFP battery is its safety. The combination of lithium iron phosphate is more stable than nickel manganese cobalt at higher temperatures. 

Plus, LFP batteries can better handle larger draws of power. Because of this, LFP batteries are less likely to experience thermal runaway. To make it short, LFP batteries are less likely to catch on fire than NMC batteries. 

This isn’t to say that if you install an NMC battery it is going to spontaneously combust. But, if an NMC battery experiences too much stress or is handled improperly, there’s a higher chance of things going awry. This is why it’s important to use a licensed, trusted installer for your battery to minimize any chances of things going wrong. 

Learn more: How SolarReviews rates solar installers in your area

Upfront cost 

Winner: NMC 

NMC batteries tend to be just a little bit cheaper than LFP batteries. This mostly has to do with economies of scale - NMC batteries are more prevalent here in the U.S., so their prices are a bit lower. 

Plus, LFP batteries are slightly bigger, so it may take some more labor to move and install them. The cabinets that hold LFP cells could also need more materials simply because of their bigger size. 

The cost difference between NMC and LFPs is definitely more of a factor when it comes to larger-scale projects. For home solar, you can usually find both types of chemistry in the same ballpark. 

Value 

Winner: LFP 

We did just say that NMC batteries cost less upfront, however, LFP batteries give you a little more bang for your buck. 

It’s important to consider how much electricity you’re able to get out of your battery to truly determine what’s the best value, and in many cases, LFP batteries come out on top because of their longer lifespan. 

The easiest way to explain this is with an example. Let’s compare the sonnenCore battery with the LG Chem Prime:

*Estimated amount of electricity the battery will discharge before the battery drops to 70% of its initial capacity

As you can see, you can get almost twice as much use from the LFP sonnenCore as you can from the NMC LG Chem Prime, so the extra money you'll spend upfront is worth it. Not only that, but you get some peace of mind knowing how safe LFPs are, all without having to sacrifice performance.

And the winner is…

Based on the overall value, we would recommend looking into LFP batteries for your solar storage system. Even though they might have a slightly higher price tag, LFP batteries last longer, have better safety ratings, and perform just as well as NMC batteries on most metrics. 

But that’s not to say you should flat out avoid NMC batteries. NMC batteries still do a great job at storing solar energy, so if it’s easier for you to get your hands on one, by all means go with the NMC. You may also want to consider an NMC battery if you’re limited on how much space you have to install a battery.

It’s more important for you to choose the right installer than it is for you to choose the right battery chemistry. A reputable local battery installer can help you all along the way so you can find the right size, type, and priced battery for your unique situation. They’ll also make sure you have the highest quality installation possible to ensure your home’s safety.

To find out more about how a solar battery installation can impact your wallet, check out our solar battery calculator.