Are lithium-ion solar batteries the best energy storage option?



lithium-ion batteries for solar storage
The LG Chem RESU is a popular lithium-ion battery for home solar. Image source: PRNewsWire

Lithium-ion batteries are becoming a popular option for home energy storage. Llithium-ion batteries can store energy to be used later, like during a power outage. When paired with solar panels, excess solar energy produced during the day is stored in the battery and is then used by a home at night when the solar panels are generating electricity. 

Lithium batteries are the most common residential battery choice because they last long, require little maintenance, and don’t take up as much space as other battery types. They typically cost between $12,000 and $20,000 to install and, in some cases, can save homeowners extra money on their electricity bills. 

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    What is a lithium-ion solar battery?

    Lithium solar batteries are a rechargeable energy storage solution that can be paired with a solar energy system to store excess solar power. Lithium-ion batteries are commonly used in rechargeable electronics like cellphones and in electric vehicles (EVs). 

    In 2015, popular EV manufacturer Tesla announced their new lithium-ion solar battery, Powerwall 1,  inspired by the technology used in their EVs. 

    The launch of the Powerwall 1 ignited a torrent of discussion and research about energy storage and the development of cost-effective solar batteries. It also propelled Tesla to be one of the top battery manufacturers in the U.S. Powerwall paved the way for the future of lithium-ion solar batteries - establishing pricing of battery energy storage, driving investment in the energy storage sector, and creating hope that battery technology could become affordable for average residential customers. 

    Prior to the development of the Tesla Powerwall, most solar storage systems were composed of lead-acid battery banks. However, there are now many lithium-ion solar batteries on the market so that every homeowner can find the right option for them. 

    But despite all the hype about this new technology, the industry and analysts alike have forgotten to ask one simple question. Are lithium-ion solar batteries the best battery for solar panel systems?

    Solar expert Will White explains how lithium-ion batteries work in the below video:

    How much do lithium-ion solar batteries cost?

    The biggest concern most homeowners have is how much an energy storage system will cost them. The total cost to install a lithium battery storage system could be anywhere from $7,000 to over $30,000

    The price can vary, depending on:

    • What manufacturer you choose
    • The features the battery has
    • How many batteries you need
    • The installation costs

    The cost of installing lithium-ion batteries is much higher than the cost of installing lead-acid batteries. A lead acid battery installation could run you anywhere from $5,000 to a maximum of $15,000 - much lower than the installation cost of lithium-ion solar batteries. 

    So why do people continue to choose lithium-ion batteries? The higher price tag comes with a lot of added benefits that you can’t get with lead-acid batteries, which justifies the higher cost for some. 

    How much can you save annually with solar-plus-battery-storage?

    Popular lithium ion solar battery brands

    There are many lithium-ion solar batteries on the market. The most popular choice for residential energy storage is the Tesla Powerwall, a 13.5-kilowatt hour (kWh) lithium-ion battery that costs about $11,500, including installation costs when purchased with Tesla solar panels. 

    The Tesla Powerwall is one of the cheapest lithium-ion solar batteries, which is one of the reasons it is so popular.

    The following table outlines some other popular lithium-ion solar batteries on the market:

    Battery Price Storage Capacity Warranty Buy
    LG RESU10H Prime $7,000 9.6 kWh 10 year Buy Now
    Tesla Powerwall $9,200 13.5 kWh 10 year Buy Now
    sonnen Ecolinx $33,000 12 kWh 15 year Buy Now
    BYD Battery Box H-10 $6,525 10.25 kWh 10 year Buy Now

    What are the pros and cons of lithium-ion solar batteries?

    The reason why the introduction of lithium-ion solar batteries rocked the solar industry is that the technology offers a variety of benefits over lead acid batteries. 

    However, there are some cases in which a lead acid battery might be a battery choice to store your solar power. 

    Pros of lithium-ion solar batteries 

    The advantages of lithium-ion solar batteries include:

    • Higher depth of discharge
    • Long lifespan
    • Higher energy density
    • High efficiency
    • Less maintenance

    Higher depth of discharge (DoD) 

    The DoD of a battery is the amount of the stored energy in the battery that has been used, as compared to the total capacity of the battery. Most batteries come with a recommended DoD in order to maintain the health of the battery. 

    Lithium-ion solar batteries are deep cycle batteries, so they have DoDs of around 95%. Many lead acid batteries only have a DoD of 50%. This means you can use more of the energy that’s stored in a lithium-ion battery without having to charge it as often. 

    Long lifespan 

    Because lithium ion batteries have a high DoD and don’t need to be charged and recharged as often, they have a long lifespan. 

    Most lithium-ion solar batteries have a minimum warrantied lifespan of around 10 years, or a cycle life of 10,000 cycles - whichever comes first. Lead acid batteries, on the other hand, only have warrantied lifespans of around 5 years. 

    Higher energy density 

    The energy density of a battery is how much power the battery can hold relative to the physical size of the battery. 

    Lithium-ion batteries can store more power without taking up as much space as lead-acid batteries, which is great for homes where space is limited. 

    High efficiency 

    Lithium-ion batteries have a higher round-trip efficiency rating than other types of solar batteries on the market. 

    Efficiency refers to the amount of usable energy you get out of your battery compared to how much energy it took to store it. Lithium-ion batteries have efficiencies between 90 and 95%. 

    Less maintenance 

    Not having to worry about regular maintenance is one of those advantages that you just can’t put a price on.

    Lithium-ion solar batteries do not require as much maintenance as flooded lead-acid batteries do.

    Cons of lithium-ion solar batteries

    The disadvantages of lithium-ion solar batteries include:

    • High cost
    • Thermal runaway

    High cost 

    Lithium-ion batteries tend to be the most expensive battery storage option, especially when compared to lead-acid batteries. 

    The good news is that solar battery systems qualify for incentives like the federal tax credit, which helps make lithium-ion batteries more affordable. Plus, although lead acid batteries may be cheaper - they have to be replaced more often than long-lasting lithium-ion systems. 

    Thermal runaway 

    Lithium-ion batteries run a higher risk of thermal runaway, which means they catch on fire. However, the risk of a properly installed lithium ion solar battery is slim to none.

    How are lithium-ion batteries recycled?

    Batteries are recycled by being shredded and mixing all of their components. Once all of the metals are mixed into a powder, they need to be separated by either being liquified or dissolved in acid so that the desired metal can be retrieved.

    Since the process of recycling batteries is still in the early stages, the United States has suggested an enhancement to the Defense Production Act. The goal is to put money towards securing the metals we need for a clean energy transition while also researching and investing in recycling lithium-ion batteries.

    Alternatively, instead of shredding old batteries, sometimes batteries within an EV can be reused. Lithium-ion batteries have a very long lifespan, and while they will lose their ability to power a car, they can still be used for less intense energy storage needs, like backup power.

    Currently, when you replace technology such as your EV or storage battery, recycling the old one is a chore. You can find certified electronics recyclers through the EPA website. Alternatively, some manufacturers like Tesla will take back their lithium-ion batteries at the end of their life to be recycled.

    What makes recycling lithium-ion batteries a challenge?

    At this stage, current recycling methods are not sophisticated enough to extract most of the key metals that can be reused in a way that is more cost-effective than mining.

    It is cheaper to mine most metals found within a lithium-ion battery than recycle them. Perhaps ironically, cheap lithium mining is one of the many reasons we can invest heavily in batteries. Unfortunately, if we build cheap lithium batteries that are not recycled, we will end up with landfills full of electronic waste.

    While recycling batteries may require some extra work and additional cost, the metals within the batteries are durable and usable. Recycling needs to become economical to reduce our dependency on freshly-mined lithium.

    Since lithium mining emits a high amount of CO2, using lithium and other metals from recycled batteries is a more environmental and sustainable alternative.

    Additionally, a potential shortage of metals that are used in batteries is looming. Discovering a way to reuse all the metals within old batteries will help meet supply needs.

    When is a lithium-ion solar battery the best choice?

    Lithium-ion solar batteries are the best solar energy storage system for everyday residential use because they take up little space while still storing a substantial amount of energy. Also, their high DoD means you can use more energy stored. 

    The battery will last longer, so it won’t need to be replaced as often as a lead acid battery. Plus, their higher efficiency means that you get to use more of the energy your solar panels produce and store - giving you more bang for your buck.

    However, in some cases, other battery types, like lead acid batteries, could work better for you. This is especially true if you are just using a solar battery as backup power storage. Since you won’t be draining a backup battery regularly, the lower DoD and lifespan don’t matter as much, so spending the extra money for those features won’t be necessary. 

    Lead acid batteries are also popular for off-grid solar system projects that aren’t used regularly - like vacation cabins. But for everyday use, spending extra on a lithium-ion solar battery is probably your best bet. 

    Whether it’s for off-grid battery backup or for a grid-tied solar system, energy storage can help you run entirely on clean energy. Contact local solar installers to find the best solar battery system to pair with your solar panels. 

    See how much solar panels will cost for your home

    Key takeaways

    • Lithium-ion batteries are rechargeable batteries that can be paired with solar panels to store excess solar energy.
    • Lithium-ion solar batteries usually cost around $9,000, but the price tag can run up to $30,000 depending on the manufacturer, included features, and how many batteries you need.
    • Lithium-ion batteries have become more popular for solar installations than lead acid batteries because they have a longer lifespan, can store more energy, and are more efficient.
    • There are some negatives to lithium-ion batteries - they come at a high cost, and they are more likely to catch fire than lead acid batteries.
    • Overall, lithium-ion batteries make the best energy storage solution for everyday residential use.
     - Author of Solar Reviews

    Catherine Lane

    Written Content Manager

    Catherine is the Written Content Manager at SolarReviews. She has been researching and writing about the residential solar industry for four years. Her work has appeared in Solar Today Magazine and Solar Builder Magazine, and has been cited by publications like Forbes and Bloomberg.

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