Which batteries are best for solar? Lead acid or lithium?

Which batteries are best for solar? Lead Acid or Lithium?

If you’ve done any research on batteries for solar energy storage you understand that topic can get as heated as politics and religion. Just the other day I shared a post on my facebook page regarding solar generators and turns out, the very first comment started a huge solar battery debate.

Whether you’re going off-grid or looking for solar backup, finding the right type of battery for your solar energy storage is just as critical as sizing it correctly. 

In this article we’ll compare the two main battery types used in off grid and solar backup systems: Lead Acid and Lithium Ion. We’ll compare their pros and cons, and share which battery is best in which type of situation. 

Here’s the summary:

LEAD-ACID is a tried-and-true technology that has been used in off grid energy systems for decades.  While they have a relatively shorter life span than lithiums, they are also 1/3 of the price tag.  They are heavy and bulky, and depending on the type, may require regular maintenance.  Overall, they’re a great battery for off-grid and backup systems.

LITHIUM is a lighter, more compact battery with a longer lifespan. They do have temperature limitations and are more expensive than their lead-acid counterparts. 

Let’s go over the pros and cons of each option in more detail, and explain why you might choose one over the other for your system.

Lead Acid

There are many variations of lead acid batteries, each designed for it’s own particular application. Generally speaking, lead acid batteries are broken down into two main categories: Flooded (FLA) and Sealed (SLA). 

– Flooded Lead Acid (FLA)

FLA batteries are the most common lead acid battery type and are widely used in the automotive industry. Until recent years, they have been the battery of choice for many off grid systems. The biggest upside to FLA batteries is the cost. They have the least cost per amp-hour vs. any other battery.
The downside however, is their need for regular maintenance. Although they are very reliable if maintained properly, maintenance could be quite time consuming if you have a large enough system. Failing to provide regular upkeep can shorten the life of the battery and void the warranty. Also, since FLA batteries aren’t sealed, they need to be installed in a ventilated enclosure to allow battery gases to escape.

Flooded Lead Acid battery


  • Lowest upfront cost
  • Reliable


  • Requires regular maintenance
  • Releases fumes
  • Temperature sensitive
  • Is not spill-proof

– Sealed Lead Acid (SLA)

Sealed Lead Acid batteries come in two types: AGM (Absorbent Glass Mat) and Gel. Both have similar characteristics, however, for this article we’ll focus on AGM batteries since they are more commonly used in solar applications.

Absorbent Glass Matt (AGM) battery is a type of lead acid battery in which the electrolyte is absorbed into a fiberglass mat and thus lowering it’s internal resistance. As a result, AGM batteries can handle higher temperatures and self-discharge more slowly than other types of batteries. This also makes them higher in efficiency (comparable to lithium batteries, which is around 95%, as compared to 80% or less for FLA batteries).

solar battery
AGM deep cycle battery

AGM batteries are self-contained so they don’t need to be refilled with water, like FLA’s. For that reason, they are a great choice for properties that aren’t occupied full-time, like an off-grid vacation cabin. 

Other advantages of AGM batteries are that they can withstand a wide temperature range, are very cost effective, have a long life span (up to 10 years), and can be used safely without spilling or releasing toxic fumes.

In recent years, solar marketing has put so much focus on lithium batteries that to use anything else in your off grid system is to say that you know nothing about solar. This is certainly not true of AGM batteries. Overall, due to their wide range of advantages, they are a great option for off grid power systems.


  • Requires minimal maintenance
  • Sealed, making them spill proof and safe
  • High efficiency
  • Larger temperature range
  • Long life span (up to 10 years)
  • Easy to replace or add more batteries


  • Heavy and bulky compared to lithium
  • Short life span if deep cycled daily
  • Needs to be kept full (float charged) when not in use, or charged often when not in use

lithium ion

Like FLA batteries, Lithium batteries come in a variety of technologies. The best technology for solar applications is Lithium Iron Phosphate (LiFePO4). This technology is safe, stable, and maintenance free for years. Lithium’s can also be put through deeper cycles than FLA or AGM batteries.

Lithium batteries are lightweight and compact, making them a great option for portable energy storage. Other advantages include: A long life cycle (3000-10,000 cycles) and higher charge and discharge efficiencies. It also looses less capacity when idle, which is useful for solar backup systems where energy is only used occasionally. 

The biggest disadvantage to Lithiums is cost. A lithium solar battery can cost up to 4 times as much as a FLA battery and 3 times as much as an AGM battery system.

Lithium Iron Phosphate (LiFePO4) battery


  • Requires no maintenance
  • Sealed, making them spill proof and safe
  • High efficiency
  • Longest life span (up to 15 yrs)
  • Lightweight and compact
  • Stays charged longer
  • Can be charged faster in less time


  • Highest cost
  • Smaller temperature range
  • More difficult to replace or add more batteries

key factors to consider when choosing a solar battery

#1 Battery Life

The life span of your solar battery is dependent on two things: Life cycle and age.

1. Life Cycle:  When you discharge a battery by using it’s power, and then charge it back up again, that is referred to as one charge cycle. The number of charge cycles your battery can handle before it begins to degrade is dependent on the type and quality of battery, as well as depth of discharge (see #2 Depth of Discharge).

2. Age of Battery: Your battery will degrade over time even if you’re not using it. 

The battery life is determined by which of these two factors come first.  For example, if your battery is designed to last up to 10 years, the battery will last 10 years if it is not heavily cycled. However the same battery may only last one year if heavily cycled (see #2 Depth of Discharge).

Depending on the quality of battery, lead based batteries will last anywhere from 3-10 years of age. Compare that to lithiums which last 7-15 years.

(More information on battery life and capacity loss can be found here).

#2 Depth of Discharge (DoD)

Depth of discharge refers to how much overall capacity is used before recharging the battery. For example, if you use half your battery’s capacity, the DoD would be 50%.

Every battery has a life cycle dependent on the depth of discharge. For example, a true deep cycle AGM battery will have a life cycle of 350 cycles at 100% DoD OR a life cycle of 3,500 cycles at 10% DoD. This means you can cycle the battery at 10% DoD every day for 9 1/2  years OR cycle it 100% for one year before affecting the life of the battery.

Now compare this to a lithium battery. A high quality Lithium Iron Phosphate (LiFePo4) battery can be cycled 4,000 times at 100% DoD or 12,000 times at 10%. This means you can cycle the battery 100% every day for 10 years and 10% for 32 years before affecting the life of the battery. By the way, AGM or Lithium won’t last much longer than 10 years (15 at the most) due to ageing.

As you can see, if you are going to be cycling your batteries every single day at 100% DoD, then paying twice the cost of lithiums to get 10 times the battery storage would be worth it.  However, most off grid systems are sized big enough for a daily 15% DoD or less, unless there is an extended time without sun.

Many batteries have a recommended DoD.  Beyond that point, you risk negatively affecting their performance and lifespan. For off-grid systems, it’s important to size your battery bank based on useable battery storage which is determined by depth of discharge. For example, if your DoD recommends not going over 50% then you need to have twice the battery size as one that can handle 100% DoD.

(More about Depth of Discharge can be found here).

#3 Efficiency

Simply put, efficiency of your solar system is how much of your solar power is actually being stored and used. 

As an example, FLA batteries are only 80-85% efficient depending on the type and condition. That means, if you have 1,000 watt hours of solar coming into the batteries, only 800-850 watt hours are available after charging and discharging. 

Lithium and AGM batteries are more than 95% efficient. Using the same example, you’d have over 950 watt hours of power available, as compared with the Flooded Lead Acid batteries.

Depending on the configuration of your system, higher efficiency could mean getting the same amount of energy use and storage in a smaller system, thus saving you more money in the long run.  

#4 Cost

There are two costs you need to consider when doing an off grid system: Upfront cost and long term cost. Many people are so focused on the upfront costs that they don’t think about any long term costs that can affect their decision of battery storage.

Upfront cost is what you initially pay for your battery bank. Long term cost is what you end up paying for batteries throughout the life of your system. 

For example, let’s say you want to save money and design a minimal battery bank that only has enough power for sunny days, and use a gas generator as backup on cloudy days. For this scenario we will calculate upfront and long term costs for both an AGM and Lithium battery bank.

In this scenario, since our battery bank isn’t large enough to cover cloudy days, we will be cycling our batteries 80% DoD daily.  This means our Lithium Iron Phosphate will handle 15,000+ cycles, which equals 41 years, or more realistically, the life of the battery which is 15 years (due to ageing). This means the battery bank will need to be replaced once in 20 years.

Compare this with the AGM’s which will last 500 cycles at 80% DoD, which means they will only last 1 1/2 years. As a result, in 20 years you will need to replace your AGM battery bank 12 times to equal the same life span as the lithiums. 

Our cost analysis for this example is running a system for 20 years.

Lithiums: Upfront cost is $7,500. Long term cost is $7,500 because we would have to replace the lithium batteries within 15 years.
Total cost = $15,000

AGM’s: Upfront cost would be $2,500.  Long term cost would be $30,000 (due to replacing the battery bank 12 times in 20 years).
Total Cost = $32,500

As you can see from our example, even though the upfront cost of lithiums are 3 times the cost of AGM’s, the long term cost is much less making the Lithium batteries the cheaper option for this example (in most cases AGM’s are actually cheaper even in the long term).

Lithium VS. lead-acid: which is best?

This answer really depends on the application.

Due to the higher cost of lithium batteries, AGM is generally a better choice for your solar energy storage, unless you specifically need the unique benefits that lithiums provide.

Here are a few situations when lithium batteries may be a better option:

  • If you need a light portable system to take on the go or to move easily.
  • If you have limited space, such as an RV or small cabin.
  • If you plan on storing your batteries for long periods of time without having them connected to solar or a battery charger.
  • If you have a small battery bank and will be putting your batteries through deep cycles on a daily basis. 

Below are some examples of various solar applications and the optimal battery for that situation. We also listed a cost analysis for each situation with a 20 year life span for the system. 

Please keep in mind that these are examples, and that there are many factors that can affect the type and cost of a solar battery bank.

Full-Time Off Grid Residence

off-grid Solar

AGM Deep Cycle

solar battery

In this situation, Deep Cycle AGM’s are usually best because of cost. With a full time off grid residence you will want to have a large enough battery bank to store plenty of power for cloudy days. As a result, 90% of the time your batteries will have a very shallow DoD (15% or less), so the AGM batteries will last almost as long as your lithium batteries at a fraction of the cost.

Cost Analysis: for 20 years

Lithium: Upfront $37,000    Longterm: $37,000  Total Cost $74,000

AGM:  Upfront $12,500    Longterm: $25,000  Total Cost $37,000

off-grid cabin or vacation home

AGM Deep Cycle

solar battery

Deep Cycle AGM battery is most likely the best for this situation, due to cost, unless you don’t have the space for AGM batteries, OR, if you plan on having a smaller battery bank and have a backup generator to run on cloudy days. If that’s the case, then you may want to go with lithium batteries because they can handle daily deep discharges and are smaller in size compared with the same capacity of AGM batteries.

Cost Analysis: for 20 years

Lithium: Upfront $18,000    Longterm: $18,000  Total Cost $36,000

AGM:  Upfront $6,000    Longterm: $6,000  Total Cost $12,000

battery backup system

AGM Deep Cycle

solar battery

The best choice in this situation is AGM, mostly due to cost. Since it will only be used occasionally, they will last nearly as long as lithium batteries at a fraction of the cost.

Cost Analysis: for 20 years

Lithium: Upfront $18,000    Longterm: $18,000  Total Cost $36,000

AGM:  Upfront $6,000    Longterm: $6,000  Total Cost $12,000

RV or Tiny Home

tiny home solar


Due to space limitation in a tiny home and RV, lithium batteries would be the better option due to their lighter weight and smaller size. Also, if you don’t use your RV for many months at a time, the lithium batteries can stay charged longer without maintenance. 

Cost Analysis: for 20 years

Lithium: Upfront $3,000    Longterm: $3,000  Total Cost $6,000

AGM:  Upfront $1,000    Longterm: $1,000  Total Cost $2,000



Lithium batteries would be best for a lightweight, portable system to take camping (as long as the weather is above freezing). If you plan on using your battery bank in freezing temperatures, opt for AGM batteries due to their ability to handle the colder temps. 

Cost Analysis: for 20 years

Lithium: Upfront $1,500    Longterm: $1,500  Total Cost $3,000

AGM:  Upfront $500    Longterm: $500  Total Cost $1,000


  1. Frank White on February 28, 2022 at 7:46 pm

    This message was answered nearly a year ago (March 26, 2021).
    “ Our current Titan does not have Bluetooth or WiFi, however, our Titan 2.0 will have WiFi. We don’t have a specific release date or price for this newer model. More information will be released before pre-sale.”
    Is the 2.0 Titan out or is there and expected release year or month?

    Thank you!

    • David Willis on March 1, 2022 at 5:54 pm

      We have had a lot of delays due to everything going on. We are still working on it, but don’t have a release date yet. I am sorry I don’t have anything specific for you yet.

  2. Chris Backus on December 23, 2021 at 3:10 am

    What is the actual temperature range for the Point Zero Lithium batteries used with the Titan? I thought there used to be an article up here about being super careful not to use the Titan battery in cold weather, I can’t find it now anywhere. How should we cope with this? I live in a fairly moderate climate (Seattle), but it can get cold down into the 20s. I see some recommendations to not use below freezing. So 32 deg F is this limit for use? What does this mean? I just can’t charge and discharge, or I can’t keep it unused at this temperature? Is it dependent on how long it’s at that temperature? Please give us more detailed guidance, as many of us have our electrical panels in our garages where it’s not heated, and we have our grid transfer switch there as well. It’s really inconvenient to move our set/up inside. Please give us some details on how and what we should be doing? Thanks!

    • David Willis on December 23, 2021 at 10:00 am

      The Titan battery has built in safety measures, so if the battery is under 32 deg, it will stop allowing it to charge. So it is safe to use it, but when it is cold, you will not be able to charge it. If you need to be able to charge when it is below freezing, I would suggest using some sort of heater to warm up the batteries. Some people have used small animal heaters, since they don’t get too hot. If it is just once in a while and you can get buy without charging until it warms up, then I would not worry about it. But to be clear you cannot damage the battery due to it’s safety measures that are built in.

  3. Buyprobattery on September 20, 2021 at 5:05 am

    Hey Thanks for sharing this amazing information, both lead-acid and lithium batteries are out in the market, my very own tesla electric model car used lithium acid battery, which gives me great milage on the go, i guess both batteries play a major role in their own terms, but the pros and con’s you mentioned in detaied is flawless, which even cleared my very own thoughts about it, keep up the good work you guys are really making a difference in this world.

  4. Daniel Ryan on August 29, 2021 at 11:40 am

    I intend on purchasing a Goal Zero Yeti or something similar to it and will be putting together a DIY solar panel array. I built an E-Bike this summer and would like to make it truly efficient by getting its energy solely from a sustainable source. My question is regarding the battery types available. There are lead acid and lithium varieties available for the models I am looking at. My question is regarding overall longevity. I know that lithium ions have a longer lifespan but are slightly harder to recycle. The passive power loss is negligible due to the natural lead acid inefficiency and the li-ion’s needing a BMS. I am looking for both longevity/future-proofing. I am seeing a lot regarding these new silica batteries and their potential to replace li-ion in the near future, for this reason I am leaning lead-acid for the simplicity/potential use as a secondary system once the silica batteries are in production. Is there any reason I would want to get a li-ion storage system in 2021 vs a lead acid?

    • David Willis on August 30, 2021 at 9:36 am

      I assume you are talking about a power system (similar go the Goal Zero yeti, and not for your E-bike? If for the E-bike, then Lead-acid would be too heavy, but if it is a system where you don’t care about the weight, then There is no problem using Lead-acid (as long as you keep them maintained). The Li-ion’s will last longer, but are also more expensive, so that part is basically a wash, unless you are deep cycling them every day, or if you will not be able to keep them fully charged most of the time. If that were the case, then I would go with li-ion. But if you will only do shallow cycles most of the time, the Lead-acid will be fine.

  5. james william on February 15, 2020 at 9:38 am

    I am currently working on a research about Solar- hybrid off-grid installations,
    I have my battery amp hour for 20hrs discharge but I need the battery to store charge for 3 days, so ut is tripled, do I still use the C20 rating or do I use the C72hrs rating for it? I am confused. and the needed Current is about 6000Amp-hour

    • David Willis on February 17, 2020 at 6:26 pm

      I am not sure what you are doing. Do you need to run 6,000 amps for 72 hours? Or is it a total of 6000 ah that you will use in a 72 hour period? Is it a constant draw, or do you store it for 3 days, then use it all quickly?

      If it is a steady draw of 83 amps for 72 hours (total of 6000 ah), then you could use the c72 rating on the battery, and just get a total of 6000 ah. However it also depends on how often you will perform this cycle, and the battery type. Most batteries (lead based) you don’t want to use the full capacity often, or you will wear them out quickly. If they are lithium iron phosphate, then you can do this using the entire capacity, and they will still last a long time.

  6. Earl Adams on July 26, 2019 at 12:19 pm

    Hello, can lithium batteries be used with your system?

    • David Willis on July 26, 2019 at 2:01 pm

      Yes, there are lithium versions for our solar generators. Our homegrid 3000 and homegrid 5000HD can be setup to use LiFePo4 (long lasting but heavier), and our new Titan solar generator which will be coming out soon uses an NMC battery (similar to Tesla), in order to make it light weight.

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