Home solar battery backups are becoming more popular as homeowners realize their benefits. By adding a solar battery backup to your system, you get:

  • Peace of mind that you can power your home with solar during grid outages*.
  • The ability to use solar energy at night and possibly reduce your electricity bills**.
  • More control over when you draw power from the grid and when you rely on solar energy.

How long do solar batteries last?

Most solar batteries have a lifespan of five to 15 years, but some can last 20 years. Keep in mind that these numbers are estimates. The reality boils down to the quality of the battery, as well as how closely you follow the manufacturer’s recommendations for usage and maintenance.

Understanding the lifespan of solar battery backups is important, because it can help you choose the right battery for your family’s usage and needs. There are different factors that affect a solar panel battery’s longevity. Fortunately, you can find the information you need about this topic right here. Just keep reading.

Factors that affect home solar battery lifespan

When it comes to deciding which solar backup battery to get, you should keep the following factors in mind. They play a major role in how long a solar battery lasts.

Type of solar battery

Since different types of solar panel batteries are made with different technologies, they have varying projected life spans based on their technology. The technology, along with your family’s energy needs and anticipated usage pattern, will help determine what kind of battery is best. And as with anything else, you’ll also need to factor in your budget. Speaking with a reputable solar backup battery installer will improve your chances of finding the most suitable battery for your family. They can also provide more clarification to answer the question, how long do solar batteries last?

Lead-acid batteries

With usage dating back to the 1800s, lead-acid batteries were one of the first on the market and they are still very common. Almost every car that runs on gasoline uses a lead-acid battery to start. Lead-acid batteries used for home backup are a specific type called “deep cycle.” Instead of giving off a lot of energy very quickly like your car battery, deep-cycle batteries put out less current but do it for a much longer time. Additionally, lead-acid batteries are sold at a lower price point than their newer counterparts.

One challenge with this type of battery is that they can give off toxic fumes, so they need to be stored carefully.

While lead-acid batteries are more affordable upfront, they have a comparatively short lifespan. They can last anywhere from three to 10 years depending on factors like how well they’re maintained, how much they’re used and whether they have a flooded or sealed design.

Lead-acid batteries are available in two different versions, each with a slightly different average lifespan:

  • Flooded—15 to 20 years.
  • Sealed—Three to 12 years.

Keep in mind that these are averages. Battery lifespan is also affected by variables like maintenance and usage.

Lithium-ion batteries

If you have a laptop or a cell phone, you’ve worked with technology that has a lithium-ion battery. These batteries are used in many different applications, because they can hold a larger amount of energy in a smaller space than lead-acid batteries. They’re also lighter and more compact in comparison. Once a lithium-ion battery is installed with your solar panel system, you won’t have to worry about maintaining it regularly. The technology requires minimal maintenance.

Best of all, lithium-ion batteries have a long lifespan—typically 10-15 years. In some cases, with proper usage and (minimal) maintenance, they can last up to 20 years. Credit for this advantage goes to a higher depth of discharge (DoD), which means you can use more stored energy before you need to charge them. We’ll go into greater detail about the depth of discharge further down.

Cost is one of the few drawbacks of lithium-ion batteries. They tend to be more expensive than their counterparts. That said, since they have a long lifespan and high depth of discharge, lithium-ion batteries are cost effective in the long run. Plus, the price of these batteries has been decreasing in recent years.

Lithium-ion is an excellent battery option for residential solar use overall. It’s one of the reasons why ADT Solar installs the Enphase IQ battery backup system. Features like Power Start™ technology, weather alerts, battery prioritization and load control set Enphase apart from other lithium-ion batteries.


Saltwater batteries

Saltwater batteries differ from lithium-ion batteries in terms of chemistry. They use sodium in a saltwater solution as a conductor, while lithium-ion batteries use lithium. A relatively new battery technology, saltwater batteries also rely on saltwater electrolytes as a means of collecting, storing and discharging energy.

Benefits of these batteries include being non-toxic and non-flammable. They’re also easier to recycle, thanks to the lack of toxic materials and heavy metals in their composition. And saltwater batteries have a long lifecycle, which means you’ll need to replace them less often. They can last anywhere from five to 15 years, depending on the model.

These advantages are great, but there are some disadvantages you’ll need to consider. First, as one of the newer technologies on the market, saltwater batteries are expensive. In addition, they’re currently being produced on a small scale, another factor that drives up their price. A lower energy density is another concern around saltwater batteries. They store less energy than lithium-ion batteries, for example, in the same amount of space. It’d take a larger saltwater battery to store the same amount of energy as a smaller lithium-ion battery.

Battery usage

You might’ve noticed that the battery in your cell phone loses its charge faster with age and use. The same is true of solar panel batteries. The more frequently the battery is charged and discharged, the shorter its lifespan becomes. This is known as the usage pattern.

Battery performance degradation over time is inevitable. By taking care of your battery, you can maximize its lifespan. One way of doing so is by not discharging or depleting the battery completely. Otherwise, you can reduce its lifespan significantly.

Usage pattern is something that affects every type of battery. The good news? You do have some control over this factor of its lifespan. Just make sure you recharge the battery before it gets depleted.

How you use your solar battery also makes a big difference. If you reserve it as a backup for power outages, the battery will last longer because it goes through fewer cycles. On the other hand, if you use it to power your home every night, the battery will wear out more quickly.

Depth of discharge (DoD)

As we briefly touched on above, a battery with a higher depth of discharge (also known as DoD) allows you to use more of the energy that’s stored in the battery. Depth of discharge is the percentage of a battery’s capacity that can be used without significantly shortening its lifespan. Managing the depth of discharge to make sure your battery has a long life can be complicated, but most modern lithium-ion batteries have sophisticated software that takes care of it.

Lithium-ion batteries, as mentioned above, typically have an excellent DoD that’s 100% or close to it. (1) A higher percentage is always better when it comes to depth of discharge. This is another factor to consider when answering the question, how long do solar batteries last?

What is round-trip efficiency?

In simple terms, round-trip efficiency (RTE) is a measurement of how much energy a battery supplies compared to how much energy it takes to charge it. A 70% RTE means you get back 70% of the energy you put in a battery.

Solar panel batteries lose efficiency with each cycle they undergo. This is the reason why you should choose one with a high round-trip efficiency. The Enphase IQ Battery 3 is a perfect example, with a DC RTE of 96% and an AC RTE of 89%.

Battery life cycle

The number of charge and discharge cycles a battery completes before its capacity degrades significantly is known as battery cycle life. This process happens gradually, with the capacity decreasing slightly each time the battery is charged and discharged. The more times the charge-and-discharge cycle happens, the more the battery’s overall capacity will degrade. Eventually, the performance of the battery will be significantly affected.

Several factors affect how many charge-and-discharge cycles a battery can go through until noticeable degradation occurs, including:

  • Type of battery
  • Temperature
  • Depth of discharge
  • Charging/discharging rates

Seasonality and temperature

Both hot and cold temperatures can adversely affect your solar battery backup’s lifespan. They can reduce its capacity over time in a few different ways. Temperatures exceeding 90°F can cause the battery to overheat, while temperatures below 32°F force the battery to work harder and need a higher voltage to charge. Neither one of these scenarios is good for the battery’s longevity.

Changes in usage pattern also impact how long a solar battery lasts. Seasonal conditions can drive these changes. For example, homeowners that live in an area that gets long, sunny days might discharge and recharge the battery more frequently during the summer months than the winter months.

A reputable solar installer will know this and will take your local climate into account. They’ll find the placement and location on your home that offers the battery the most protection from extreme temperatures.

Maximize solar battery lifespan

Whether you’re considering getting a solar energy system with a backup battery or adding a solar battery backup to your existing system, understanding solar backup battery lifespan is key. When you have this information, you can take the measures necessary to maximize how long your solar battery lasts—or choose the battery with the longest lifespan for your family’s energy needs, if you’re shopping around for one.

Following the battery manufacturer’s usage recommendations will also help maximize its lifespan. Keep this information handy so you can refer to it whenever you need it.

A Solar Energy Specialist can walk you through solar panel battery lifespan and answer your questions. Schedule a consultation to speak with one of our helpful experts.