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

Iceland and Paraguay might seem entirely different on the surface, but they have one thing in common: they're almost 100% reliant on renewable energy. 

So why do large nations like the US find it difficult to reach just 20% of energy generation from renewables? There are many answers to that question, but one you’ll often see is because renewables are an intermittent power source - meaning, they aren’t reliable enough to run a whole country. 

This is partially true. The two major forms of renewable energy - solar and wind power - are considered intermittent resources, as the sun isn’t always shining and the wind isn’t always blowing. However, new energy storage technologies, like lithium ion solar batteries are making it possible to power homes with solar energy 24/7. 

In this blog, we’ll explain lithium ion solar batteries, see how much they cost, review popular brands, and discuss their pros and cons. 

On this page:

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 every homeowner can find the right option for them. 

But despite all the hype of 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 $12,000, including installation costs. 

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 battery on the market:

Battery Price Storage Capacity Warranty Buy
LG Chem RESU $6,999 9.3 kWh 10 year Buy Now
Tesla Powerwall 2 $7,500 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 because 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 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 a lead acid battery, 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 maintenance like 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, this risk of a properly installed lithium ion solar battery is slim to none. 

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 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

SolarReviews Blog Author

Catherine is a researcher and content specialist at SolarReviews. She has strong interests in issues related to climate and sustainability which led her to pursue a degree in environmental science at Ramapo College of New Jersey.

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