Best solar batteries
Making the switch to solar power can save you in energy costs, but without a way to store excess energy, good power can go to waste. Solar batteries help optimize the amount of solar energy you keep and use. With this solution, you can store any extra power your panels generate for use at night, during poor weather or in an emergency. You can buy a lead-acid, lithium ion, nickel cadmium or flow solar battery.
Our picks for the best solar batteries come from solar brands that have ratings of at least 3.5 stars on our site as of publishing. They all hold at least 9.8 kWh of power and come with warranties of at least 10 years.
Compare our top 3 solar battery picks
Lead-acid batteries are the oldest and cheapest option, but they can’t store as much energy as the others — and they have a shorter life span. Nickel cadmium batteries tend to fit commercial or big-business needs because they’re resilient against extreme high heat, but they’re also extremely toxic and even illegal in some countries.
Newer to the field and popular among homeowners, lithium batteries are convenient and lightweight. They also have a longer life span than the alternatives and require less maintenance. Flow batteries, another recent innovation, are nontoxic and use 100% of their stored energy — but they can be expensive.
All our top picks are lithium batteries.
Our top picks
- Model: SunVault
- Capacity: 52 kWh
- Warranty/guarantees: 10 years
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SunPower is a manufacturer of solar energy tech and green energy devices. Known for its efficient and dependable solar panels, the company is a popular solar power option for homeowners. SunPower also provides one of the most comprehensive solar panel warranties in the industry, though its battery warranty is in line with those from competitors.
What we like SunPower offers the highest-powered batteries in the industry, which means you can have more appliances running simultaneously and for longer periods of time with a SunVault setup. Despite the increased capacity, SunPower’s batteries run at lower temperatures and are likely to last longer without servicing. Plus, SunPower has a variety of financial options for homeowners; you can pay your fees upfront, use a loan or lease your system. What to consider SunPower’s reflect its reported quality. A SunVault battery system can cost between 12,000 to 28,000, including installation. If financing is a roadblock, you may want to consider more budget-friendly solar batteries. What reviewers say As of publishing, SunPower has a rating of 4.3 stars on our site. According to one of our reviewers, “SunPower was the best one with a warranty and that was actually able to back it up with reliability. It’s a little pricier, but for the longevity and their reliability, it’s good. That’s what sold me on that and I’m very satisfied with my decision.”
Tesla Energy is Tesla’s clean energy company. It develops fully integrated solar and battery backup roof options for both residential and commercial customers. While it hasn’t been around as long as SunPower, Tesla Energy has made a significant mark on the solar industry with its affordable batteries in recent years.
What we like Tesla’s battery is versatile thanks to its stackable output, which means you can add multiple batteries for more power. The stackable batteries are also resilient to high heat, which improves long-term performance. Tesla offers a simple and free consultation and quote process, making it accessible for many. The company provides one of the least-expensive batteries on the market, typically ranging from 7,500 to 8,500 What to consider In general, Tesla batteries take up more space than competitors’ due to the necessity of electrical boxes, so keep these dimensions in mind when you’re planning your layout. It’s also likely you won’t be able to go completely off-grid with Tesla’s backup system — total electrical independence would call for an extensive solar panel system and extra wattage. What reviewers say At the time of publishing, Tesla has a rating of 3.5 stars on our site. Happy customers like the company’s software, app and efficiency capabilities.
One reviewer from Minnesota said: “It’s such a great experience to have Powerwall installed and activated with our Solar panels. … In terms of Powerwall as a battery, there’re a few others with similar features. But Powerwall battery management software [is] absolutely the best. It makes energy storage and energy consumption back and forth smooth, with no downtime.”
- Model: LG Chem RESU
- Capacity: 9.8 kWh
- Warranty/guarantees: 25 years
Vivint Solar evolved from a home security company and now offers a wide selection of tech-forward devices, including residential solar panels in partnership with Freedom Forever. Together, the two companies create green energy solutions for homeowners.
What we like Because the LG Chem RESU uses a lithium ion battery, it can retain up to 70% of its original capacity after 10 years, meaning its performance quality should stay strong over a long period of time. The battery system also has a smaller scale than many of its counterparts, making it perfect for many design situations. Vivint Solar also provides a free security system with its products, including a thermostat, motion sensors and more. What to consider Because of its compact nature, the LG Chem RESU is typically used for smaller, residential needs and is limited in its power output. If you’re planning to support an HVAC system or large building, you may want to consider a different option. Be aware that Vivint Solar’s pricing is also less straightforward than other companies’ — it doesn’t disclose its specs. What reviewers say At the time of publishing, Vivint Solar has a rating of 3.8 stars on our site.
A reviewer in California shared: “When we signed up, the Vivint employees also took care of everything. … It was a positive experience as far as getting something installed. … This went well and they were very up to date with everything. They knew they had to get an okay from the inspector and the men from Vivint took care of all of that too.”
What is a solar battery?
A solar battery is an energy storage option for those with solar panel systems. With the increased use of solar power, solar batteries are more popular with homeowners who want to offset electricity costs and those living or camping off-grid.
Solar generators and portable solar chargers are types of solar battery storage systems. While solar generators are typically affixed to their location — usually houses, campers or boats — a portable solar charger is a smaller, often hand-held device typically used to charge phones or other electronics. Some solar generators are available as all-in-one kits, but you can buy components separately as well.
Types of solar batteries
There are multiple battery types to consider when choosing solar batteries. Which type is best varies based on your needs and whether you prioritize cost efficiency, safety or environmental impact.
Deep-cycle battery The term “deep cycle” refers to the battery’s ability to complete a discharge-recharge cycle several times. Deep-cycle batteries are designed to keep a steady flow of power over an extended period. Thick lead plates help prolong the battery’s life. Lithium-ion, flooded and gel batteries are types of deep-cycle batteries. Lithium-ion battery Lithium-ion batteries are an excellent choice because they are relatively low maintenance and easy to install. The benefits of a lithium-ion solar battery include higher energy density, less weight and increased life span. Lithium-ion batteries are considered a revolution in home energy storage solutions.
Lithium batteries have the added advantage that their voltage stays relatively constant as it discharges. In a lead-acid battery, the voltage decreases as the battery discharges. So, in order for a lead-acid battery to maintain its output, the current draw increases as the voltage drops. This, in turn, discharges the lead-acid battery more quickly. Lithium batteries do not have this drawback.
Lithium-polymer battery Similar to lithium-ion, lithium-polymer batteries are more resistant to issues like overcharge or electrolyte leakage. They are also more expensive and don’t usually last for as many cycles as lithium-ion batteries. Flooded lead-acid battery Also known as wet-cycle batteries, flooded lead-acid batteries contain liquid in an open container and disperse hydrogen gas. These batteries are cheaper but require more maintenance because the battery must be kept upright and well-ventilated. The battery also needs to be monitored and regularly refilled with distilled water. Sealed lead-acid battery This valve-regulated battery is considered the maintenance-free option in sealed lead-acid (SLA) batteries. They are designed to keep the battery from reaching its gas-generating limit while charging, which prevents water depletion and gas dispersal. This also means that the battery can never be completely charged. Nickel-cadmium battery Ni-cad batteries have a long lifespan if properly maintained. This is one of the more rugged battery types available, but they occasionally require a full discharge to keep their longevity. Be aware that cadmium is toxic, so this battery cannot be disposed of in landfills. Saltwater battery If you’re looking for clean and environmentally friendly energy, a saltwater battery is a good choice. Like lead-acid batteries, saltwater batteries offer a natural alternative for clean energy storage. The electrolyte is saltwater, which is nontoxic and nonflammable. These batteries are maintenance-free and have good longevity. Solar gel battery A gel battery, or gel cell, is similar to a sealed lead-acid battery. This battery also uses a gel electrolyte. Unlike other lead-acid batteries, you don’t need to keep it upright — it handles movement very well, which makes it a Smart choice for campers, vans and boats.
How do solar batteries work?
Solar batteries can be installed alongside your solar panel system to store the excess energy it produces. When the panels don’t produce power at night, you can use the stored energy instead. Many solar battery storage options come with an inverter to convert the stored DC power to the AC power you need, but some require you to buy the inverter separately.
You can then use it as a solar battery generator to power electricity needs. This helps people looking to mitigate electricity costs, prepare for disasters or be completely off-grid. Homes still on the electrical grid can offset their consumption with backup energy and run on battery power until the storage is depleted.
The amount of electricity a solar battery can deliver at once is measured in kilowatts (kW). Kilowatt-hours (kWh) refers to the total amount of energy utilized over an hour. The U.S. Energy Information Administration (EIA) states the average American home consumes 901 kWh per month, or 30 kWh a day. With a battery that provides 2.5 kWh, you would need 12 batteries for sufficient daily power.
Since solar batteries self-discharge, the stored solar energy depletes over time. The rate of self-discharge depends on the type and age of the battery. Newer batteries typically deplete at a rate of 1% to 2% per month, whereas older batteries could deplete by as much as 2% per week.
Residential solar panel arrays don’t usually require solar batteries. Still, solar panel battery storage lowers your utility bills, protects you from power outages and reduces your carbon footprint. If you already have solar panels, solar batteries work to store energy for the future. However, most popular solar batteries like Tesla Powerwall and LG Chem RESU aren’t designed to go completely off the grid.
FAQ
Small solar batteries run between 200 and 2,000. However, a quality battery for residential solar energy storage can cost up to 7,000 or more. When comparing solar battery prices, you should also consider the cost of battery storage per kWh (kilowatt-hour), which ranges from 400 per kWh to 750 per kWh.
Most homeowners need between two and five solar batteries to effectively power a house. Depending on your energy needs, you can connect several batteries in a series or parallel battery bank with interconnecting cables. Solar batteries are stackable, meaning that you can install multiple batteries with your solar storage system to reach the right capacity for you.
Solar panels are expensive because of the materials required to produce them. are expected to drop as solar technology advances.
Generally, fully charged solar batteries should power your home for 12 to 24 hours. Variables like your household energy consumption, the capacity of your batteries and whether you’re connected to an electrical grid determine exactly how your long solar batteries last. A solar battery’s lifespan can be anywhere between five and 15 years. You can extend a battery’s life with proper maintenance and by protecting it from extreme temperatures.
A battery bank is a collection of batteries that are connected. A battery bank allows for more power storage than you get from a single battery.
Are solar batteries worth it?
Solar batteries are an energy-efficient way to generate backup power. However, for those who just want to go off the grid, diesel generators might be cheaper in the short term. Solar batteries make a lot of sense if you live in an area where utilities are unreliable or if you want to go off the grid while using renewable energy. Solar batteries store excess energy produced by your solar energy system so that you can tap into it whenever your panels don’t produce enough electricity.
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How long do residential storage batteries last?
Multiple factors can affect the lifespan of a residential battery energy storage system. We examine the life of batteries in Part 3 of our series.
Share
In Parts 1 and 2 of this series, pv magazine reviewed the productive lifespan of residential solar panels and inverters. Here, we examine home batteries, how well they perform over time, and how long they last.
Residential energy storage has become an increasingly popular feature of home solar. A recent SunPower survey of more than 1,500 households showed that about 40% of Americans worry about power outages on a regular basis. Of the survey respondents who are actively considering solar for their homes, 70% said they plan to include a battery energy storage system.
Besides providing backup power during outages, many batteries are integrated with technology that allows for intelligent scheduling of the import and export of energy. The idea here is to maximize the value of the home’s solar system. And some batteries are optimized to integrate an electric vehicle charger.
Although deployment of energy storage is on a steady climb, attachment rates of batteries remain low. In 2020, just 8.1% of residential solar systems included attached batteries, according to Lawrence Berkeley National Laboratory (LBL).
Many options exist with multiple battery chemistries available for home energy storage. The bottom line, however, is that in the United States, two brands dominate the space. than 90% of the market is served by LG Chem and Tesla Powerwall, which are lithium-ion batteries, according to LBL. Tesla controls more than 60% of the entire market.
The Tesla PowerWall has a limited warranty that says the device will be free from defects for 10 years following installation. It also warrants that the PowerWall will start its life with a capacity of 13.5 kWh, and will retain energy capacity based on a degradation schedule.
LG claims that its system will retain at least 60% of its nominal energy capacity (9.8 kWh) for 10 years. The battery must operate between.10 C and 45 C to remain covered by the warranty. Total throughput of energy within the warranty is limited to 27.4 MWh.
Battery life
Solar installer Sunrun said batteries can last anywhere between five to 15 years. That means a replacement likely will be needed during the 20 to 30 year life of a solar system.
Battery life expectancy is mostly driven by usage cycles. As demonstrated by the LG and Tesla product warranties, thresholds of 60% or 70% capacity are warranted through a certain number of charge cycles.
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Two use-scenarios drive this degradation: overcharge and trickle charge, said the Faraday Institute. Overcharge is the act of pushing current into a battery that is fully charged. Doing this can cause it to overheat, or even potentially catch fire.
Trickle charge involves a process in which the battery is continually charged up to 100%, and inevitably losses take place. The bounce between 100% and just under 100% can elevate internal temperatures, diminishing capacity and lifetime.
Another cause of degradation over time is the loss of mobile lithium-ions in the battery, said Faraday. Side reactions in the battery can trap free usable lithium, thereby lowering capacity gradually.
While cold temperatures can halt a lithium-ion battery from performing, they do not actually degrade the battery or shorten its effective life. Overall battery lifetime is, however, diminished at high temperatures, said the Faraday Institute. This is because the electrolyte that sits between the electrodes breaks down at elevated temperatures, causing the battery to lose its capacity for Li-ion shuttling. This can reduce the number of Li-ions the electrode can accept into its structure, depleting the lithium-ion battery capacity.
Maintenance matters
It is recommended by the National Renewable Energy Laboratory (NREL) to install a battery in a cool, dry place, preferably a garage, where the impact of a fire (a small, but potential threat) can be minimized. Batteries and components around them should have proper spacing to allow cooling, and regular maintenance check-ups can be helpful in ensuring optimal operation.
NREL said that whenever possible, avoid repeated deep discharging of batteries, as the more it is discharged, the shorter the lifetime. If the home battery is discharged deeply every day, it may be time to increase the battery bank’s size.
Batteries in series should be kept at the same charge, said NREL. Though the entire battery bank may display an overall charge of 24 volts, there can be varied voltage among the batteries, which is less beneficial to protecting the entire system over the long run. Additionally, NREL recommended that the correct voltage set points are set for chargers and charge controllers, as determined by the manufacturer.
Inspections should occur frequently, too, said NREL. Some things to look for include leakage (build-up on the outside of the battery), appropriate fluid levels, and equal voltage. NREL said each battery manufacturer may have additional recommendations, so checking maintenance and data sheets on a battery is a best practice.
This content is protected by copyright and may not be reused. If you want to cooperate with us and would like to reuse some of our content, please contact: editors@pv-magazine.com.
Ryan Kennedy
Ryan joined pv magazine in 2021, bringing experience from a top residential solar installer, and a U. S.
How long do residential storage batteries last?
Multiple factors can affect the lifespan of a residential battery energy storage system. We examine the life of batteries in Part 3 of our series.
Share
In Parts 1 and 2 of this series, pv magazine reviewed the productive lifespan of residential solar panels and inverters. Here, we examine home batteries, how well they perform over time, and how long they last.
Residential energy storage has become an increasingly popular feature of home solar. A recent SunPower survey of more than 1,500 households showed that about 40% of Americans worry about power outages on a regular basis. Of the survey respondents who are actively considering solar for their homes, 70% said they plan to include a battery energy storage system.
Besides providing backup power during outages, many batteries are integrated with technology that allows for intelligent scheduling of the import and export of energy. The idea here is to maximize the value of the home’s solar system. And some batteries are optimized to integrate an electric vehicle charger.
Although deployment of energy storage is on a steady climb, attachment rates of batteries remain low. In 2020, just 8.1% of residential solar systems included attached batteries, according to Lawrence Berkeley National Laboratory (LBL).
Many options exist with multiple battery chemistries available for home energy storage. The bottom line, however, is that in the United States, two brands dominate the space. than 90% of the market is served by LG Chem and Tesla Powerwall, which are lithium-ion batteries, according to LBL. Tesla controls more than 60% of the entire market.
The Tesla PowerWall has a limited warranty that says the device will be free from defects for 10 years following installation. It also warrants that the PowerWall will start its life with a capacity of 13.5 kWh, and will retain energy capacity based on a degradation schedule.
LG claims that its system will retain at least 60% of its nominal energy capacity (9.8 kWh) for 10 years. The battery must operate between.10 C and 45 C to remain covered by the warranty. Total throughput of energy within the warranty is limited to 27.4 MWh.
Battery life
Solar installer Sunrun said batteries can last anywhere between five to 15 years. That means a replacement likely will be needed during the 20 to 30 year life of a solar system.
Battery life expectancy is mostly driven by usage cycles. As demonstrated by the LG and Tesla product warranties, thresholds of 60% or 70% capacity are warranted through a certain number of charge cycles.
Two use-scenarios drive this degradation: overcharge and trickle charge, said the Faraday Institute. Overcharge is the act of pushing current into a battery that is fully charged. Doing this can cause it to overheat, or even potentially catch fire.
Trickle charge involves a process in which the battery is continually charged up to 100%, and inevitably losses take place. The bounce between 100% and just under 100% can elevate internal temperatures, diminishing capacity and lifetime.
Another cause of degradation over time is the loss of mobile lithium-ions in the battery, said Faraday. Side reactions in the battery can trap free usable lithium, thereby lowering capacity gradually.
While cold temperatures can halt a lithium-ion battery from performing, they do not actually degrade the battery or shorten its effective life. Overall battery lifetime is, however, diminished at high temperatures, said the Faraday Institute. This is because the electrolyte that sits between the electrodes breaks down at elevated temperatures, causing the battery to lose its capacity for Li-ion shuttling. This can reduce the number of Li-ions the electrode can accept into its structure, depleting the lithium-ion battery capacity.
Maintenance matters
It is recommended by the National Renewable Energy Laboratory (NREL) to install a battery in a cool, dry place, preferably a garage, where the impact of a fire (a small, but potential threat) can be minimized. Batteries and components around them should have proper spacing to allow cooling, and regular maintenance check-ups can be helpful in ensuring optimal operation.
NREL said that whenever possible, avoid repeated deep discharging of batteries, as the more it is discharged, the shorter the lifetime. If the home battery is discharged deeply every day, it may be time to increase the battery bank’s size.
Batteries in series should be kept at the same charge, said NREL. Though the entire battery bank may display an overall charge of 24 volts, there can be varied voltage among the batteries, which is less beneficial to protecting the entire system over the long run. Additionally, NREL recommended that the correct voltage set points are set for chargers and charge controllers, as determined by the manufacturer.
Inspections should occur frequently, too, said NREL. Some things to look for include leakage (build-up on the outside of the battery), appropriate fluid levels, and equal voltage. NREL said each battery manufacturer may have additional recommendations, so checking maintenance and data sheets on a battery is a best practice.
This content is protected by copyright and may not be reused. If you want to cooperate with us and would like to reuse some of our content, please contact: editors@pv-magazine.com.
Ryan Kennedy
Ryan joined pv magazine in 2021, bringing experience from a top residential solar installer, and a U. S.