What is the best solar battery for your home?
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It’s becoming more common to install solar batteries with solar panels, especially as power outages become more common throughout the U.S.
Batteries provide significant benefits like providing backup power, and the price of installing energy storage continues to get cheaper every year. But it can be difficult to know exactly what to look for when shopping for a solar battery.
In this blog, we break down everything you need to know about solar batteries, from the most popular home batteries on the market to what features to look for so you can pick the right battery for your home.
Solar panels make more electricity during the middle of the day than they do at any other time.
The middle of the day also happens to be when homes use the least amount of electricity. Because of this, your solar panels will produce a lot of electricity in the afternoon that you won’t need.
Solar batteries are able to store that extra solar energy so you can use it later on. This lets you power your home on clean renewable energy from your solar panels, even when they aren’t producing electricity.
What’s great about installing a solar battery is that it allows you to be less reliant on the grid while ensuring you have access to reliable backup power when there’s a power outage.
Depending on the battery’s chemistry, a solar battery can cost anywhere from $200 to $15,000 to install. Residential grid-tied solar panels are usually paired with lithium-ion batteries, which tend to fall in the $7,000 to $14,000 range.
However, most people don’t have that kind of money just lying around. Luckily, batteries that are paired with solar systems are eligible for the 26% federal solar tax credit. Some states even have additional solar battery incentives, like the California SGIP program.
Although pairing solar panels with energy storage is becoming more common, it doesn’t mean it’s the right choice for everyone.
Installing a solar battery provides the greatest benefits to homeowners who live in areas that experience frequent power outages, where full-retail net metering isn’t offered, or if there are battery incentives available in your area. Solar batteries are also great if your main reasons for going solar are environmental, as it maximizes the amount of renewable energy your home uses.
However, if you’re only looking to save extra money, a solar battery might not be worth it for you. What we mean is, if you live in a state with full-retail net metering, you’ll be saving the same amount of money with a battery as you would without one. All the battery would be doing is adding thousands of dollars to your solar installation.
You can read more about how your utility net metering plans impact the investment in a solar battery here.
Lithium-ion solar batteries are the best choice for most homeowners. They don’t require maintenance, they last longer than lead-acid batteries, and they can store more energy.
Three popular lithium-ion home solar batteries are:
Let’s take a closer look at what these batteries have to offer.
Price (before installation): $8,500 Buy Now
Image source: Tesla
|Price (before installation)||$8,500|
|Price per kWh (before installation)||$555/kWh|
|Usable capacity||13.5 kWh|
|Power rating||5 kW|
|Round trip efficiency||90%|
|Warranty||70% at 10 years or 37.8 MWh throughput|
|Chemistry||Lithium Nickel Manganese Cobalt (NMC)|
The Tesla Powerwall is probably the most well-known solar battery option, and for good reason. It comes at a great price - $8,500 including the Gateway management system - and it has impressive features, to boot. When you include installation costs, the total cost of a Powerwall will be $12,000.
A Powerwall can hold 13.5 kWh of electricity. That’s about half of the average American household’s electricity usage. Other batteries of this size will likely cost you significantly more money. The battery can be completely discharged before it needs to be recharged, which means you get to use more of the power in the battery.
It has a pretty standard warranty for lithium-ion batteries: a Powerwal will operate at 70% of its rated capacity at 10 years, or after it has released 37.8 megawatt-hours of power, whichever comes first.
The biggest downside of the Tesla Powerwall is that they are no longer available for individual sale. If you want a Powerwall, it must be installed with a new Tesla solar panel or solar roof system, or with a new solar panel system installed by a Powerwall partner, like Sunrun.
This means if you have an existing solar panel system, you cannot add a Powerwall. It also means that you have to go solar with Tesla, or one of their partners, instead of being able to shop around for installers. This is a pretty big red flag for us, as Tesla doesn’t have a great track record when it comes to their long-term solar customer service.
Plus, because they aren’t for individual sale, you can’t use Powerwall for off-grid installations. They aren’t well-suited for off-grid anyway, so it’s not a huge loss if you’re looking to get off the grid completely.
Price (before installation): $5,000 - $7,000 Buy Now
Image source: Solar Power World
|Specification||LG CHEM RESU 7H||LG Chem RESU 10H|
|Price* (before installation)||$5,000||$7,000|
|Price per kWh (before installation)||$757/kWh||$752/kWh|
|Usable capacity||6.6 kWh||9.3 kWh|
|Power rating||3.5 kW||5 kW|
|Round trip efficiency||94.5%||94.5%|
|Warranty||60% at 10 years or 22.4 MWh throughput||60% at 10 years or 22.4 MWh throughput|
|Chemistry||Lithium Nickel Manganese Cobalt (NMC)||Lithium Nickel Manganese Cobalt (NMC)|
*Estimated prices, actual pricing may vary
The LG Chem RESU is another popular lithium-ion solar battery. LG’s battery comes in two different sizes: 6.6 kilowatt-hour (kWh) and 9.3 kWh. There are also different models to choose from, depending on the solar inverter you choose. Plus, the LG CHEM RESU can be used for completely off-grid solar installations.
The variation in battery models offered by LG is a huge advantage for homeowners. Unlike the Powerwall, which now requires you to install a Tesla solar panel system and Tesla inverter, the LG Chem allows for better customization of your solar-plus-storage system. Another benefit of the LG Chem is that it is charged directly with the DC power produced by your solar panels, making it more efficient.
However, the RESU isn’t able to hold as much power and has a shorter lifespan than other lithium-ion batteries on the market. LG’s warranty states that their battery will only operate at 60% of its original capacity after 10 years, or after 22.4 MWh has been released, whichever comes first.
Price (before installation): $9,500 Buy Now
Image source: sonnen
|Price (before installation)||$9,500|
|Price per kWh (before installation)||$950/kWh|
|Usable capacity||10 kWh|
|Power rating||4.8 kW|
|Round trip efficiency||>85%|
|Warranty||70% at 10 years or 58 MWh throughput|
|Chemistry||Lithium Iron Phosphate (LFP)|
The sonnenCore battery is the newest product from luxury battery manufacturer sonnen. Sonnen launched the sonnenCore battery to break into the mainstream residential storage market in 2020.
The sonnenCore costs $9,500 before installation, with a 10 kWh storage capacity and a round trip efficiency of at least 85%. Unlike the Powerwall or LG Chem, sonnenCore is a lithium-ion phosphate battery, which makes it less susceptible to catching fire and gives it longer battery life.
According to sonnen’s warranty, the sonnenCore will operate at 70% of its original capacity after 10 years, or after 58 MWh of electricity released, whichever comes first. So, while the sonnenCore will last you longer, it comes at a higher price. The sonnenCore battery cannot be used for off-grid solar installations.
Overall, you can’t go wrong with any of these batteries. But, if we had to choose, the LG Chem RESU comes out on top for us. It’s budget-friendly, you can install more than one to meet your energy needs, they’re suitable for completely off-grid solar installations, and they’re widely available.
But, LG’s technical specifications aren’t as good as Tesla’s and sonnen’s. So, if you’re looking for a battery with the best specs, go with sonnen if they’re available in your area.
The Tesla Powerwall would be our number one pick, but because you are now required to install a Powerwall with a new Tesla solar system, we just can’t say that it’s the best choice - and it’s a shame, because the Powerwall is an impressive battery.
There are four key features to keep in mind when looking for a solar battery:
Let’s break down these terms and what they mean so you can get a better idea of what to look for.
Although they are two different metrics, it’s important to look at the power and usable capacity rating together, as they indicate how much of your home a battery can power, and for how long.
The usable capacity rating tells you how many kilowatt-hours (kWh) of electricity will be stored in the battery that you can actually use. This will dictate how long your battery can send electricity to your home.
The power rating is how much electricity a battery can deliver to your home at once, measured in kilowatts (kW). This will give you an idea of how many appliances the battery can power.
Batteries with a high capacity rating and a low power rating will be able to power a few important appliances, like refrigerators and washing machines, for prolonged periods of time. These types of batteries are great as emergency backup generators.
A battery with a low capacity and high power rating will be able to power most of your house, but only for a few hours.
The depth of discharge (DoD) of a solar battery is the percentage that a battery has been discharged relative to the total capacity of the battery.
DoD sounds more confusing than it is. To put it simply, it’s the percentage of the power stored in the battery that has been used. So, if your battery holds 10 kWh of electricity, and you use 6 kWh, the DoD is 60%.
Most solar batteries have a specific DoD listed to maintain the health of the battery. For example, if you have a 10 kWh battery with a recommended DoD of 80%, you should not use more than 80% of the electricity stored in the battery. In this case, that’s 8 kWh. Using any more than 8 kWh could cause damage to the battery.
Generally, having a higher DoD rating is better, as it allows you to use more of the energy stored in your battery before you have to recharge it, which extends the battery’s lifespan.
The round trip efficiency of a solar battery represents the amount of energy you can use from your solar battery compared to the amount of energy it took to store that energy.
Say your solar panels sent 10 kWh of electricity to your battery, but only 7 kWh of that electricity was actually stored and can be used. That means 3 kWh were used by the battery’s operating system to store and release the electricity, making the battery’s round trip efficiency rating 70%.
High-efficiency batteries will end up saving you more money because more of the electricity that you produce can be used by your appliances, instead of being used by the battery to store the energy.
A solar battery’s warranty will give you an idea of how long the battery should last. Most solar home batteries have a battery life of at least 10 years with regular use.
A battery warranty will include one or more of the following metrics:
The number of years is pretty straightforward - your battery will operate at 70% of its original capacity after 10 years. Most warranties list the years because it’s easy for consumers to understand, but how long a battery will really last depends on how often the battery ‘cycles’, meaning how many times the battery was fully charged and discharged.
If they provide a cycle life, it will typically be somewhere around 10,000 cycles. So, your battery will operate at 70% of its original capacity after it has been charged and discharged 10,000 times. It sounds like a lot, but with regular use, you could easily reach 10,000 cycles before you reach 10 years.
A throughput measurement is a little more exact. The warranty will list an estimate of how much power, usually in megawatt-hours (MWh), a battery can release before the capacity drops to a certain percent of the original. This is the easiest way to compare battery warranties because it gives you a rough idea of how much electricity you can use from the battery.
The sonnenCore warranty lists all three. If you install a sonnenCore battery, it will be guaranteed to operate at 70% of its original capacity after 10 years, or 10,000 cycles, whichever comes first. sonnen estimates that the battery will be able to release 58 MWh of electricity before the capacity drops to 70%.
There are many different types of solar batteries on the market, such as flow batteries and salt water batteries. However, most residential energy storage systems have either lead-acid or lithium-ion batteries.
So, which solar battery type will work best for you?
Lead-acid batteries have been used for decades and tend to be the cheapest solar battery option. However, because of their chemistry, they require more space per kWh of storage than other batteries. This means you have to make sure you have adequate space to install them.
There are two types of lead-acid batteries:
Lead-acid batteries typically have a low DoD, somewhere around 50%, so they need to be recharged more frequently. This also impacts the battery’s lifespan - which typically falls between 5 and 10 years. So, expect to have to buy replacements for your lead-acid battery bank more often than if you chose a lithium-ion battery.
Here are some popular lead-acid batteries:
|Universal UB121000-4597 8 12v 100AH Deep Cycle AGM Battery||$179.99||Lead-acid||1.2 kWh||1-year||Buy Now|
|Trojan (SPRE 06 255)||$201.26||Lead-acid||1.4 kWh||5-year||Buy Now|
|Renogy 12-volt 100-amp-hour Deep Cycle Hybrid Gel Battery||$279.99||Lead-acid||1.2 kWh||1-year||Buy Now|
When it comes to deep-cycle batteries, lithium-ion batteries are the new kid on the block. But despite being relatively new and more expensive, lithium-ion batteries have quickly become the favorite solar energy storage option among homeowners.
One reason people are opting for lithium-ion batteries is that they are smaller and lighter than lead-acid batteries, so they take up much less space for the same amount of capacity. They also tend to have a longer lifespan, usually with a minimum of 10 years, because they have higher DoD ratings.
The biggest downside to lithium-ion solar batteries is that they are more prone to experience ‘thermal runaway’, meaning they have a higher chance of catching on fire than a lead-acid battery. But, thermal runaway is extremely uncommon and as long as it’s properly installed, the chances of your battery catching fire is almost zero.
Installing a solar battery can be a great way to get the most value out of your solar panel system. Batteries are an excellent source of backup power, they increase your energy independence, and in some cases can even save you more money on your electric bill.
However, solar battery systems do come at a price. If you’re looking to save money, installing a solar battery might not be right for you, especially if your utility offers net metering. However, if you live in an area that experiences widespread blackouts, like the ones in California and Texas, or somewhere with time-of-use utility rates, having a battery backup to store energy for when you need it will be beneficial.
The upside is that the price of solar battery technology continues to fall, so all solar power systems may be installed with storage in the future.
If you’re looking to pair your solar panels with storage, make sure you contact multiple reputable battery storage installers to ensure that you get the highest quality installation at the best possible price.
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