LG Chem RESU: The complete battery review

LG is a leader in the home electronics industry. LG's battery subsidiary, LG Chem, produces one of the most popular batteries in the U.S. market: the LG Chem RESU 10H battery. One of LG's new models, the RESU Prime, is a fully integrated energy storage system that includes an inverter and smart energy management software at a more compact size than the original. If you have solar on your property and install a home battery like the LG RESU or RESU Prime, you can store excess solar electricity to use later in the day or during power outages. As a result, properties with solar-plus-storage can increase their total monthly savings in certain markets.

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The LG Chem RESU and RESU Prime pair well with solar panel systems, especially if your utility has reduced or removed net metering, time-of-use rates, or demand charges. Installing a storage solution like the LG Chem RESU or RESU Prime with a solar energy system allows you to maintain a sustained power supply during the day or night as long as you store enough power from your panels when the sun is shining.

As with many other home battery products, these batteries are sized for day-to-day use at your home and are often paired with a home solar panel system. When your solar panels produce more electricity than you can use in your home, you can store the excess electricity in the battery system instead of sending it back into the grid. Later, when your panels aren't producing enough electricity to meet your home's needs, you can use the electricity stored in your battery instead of having to buy it from your utility company.

LG Chem RESU batteries connect directly to your solar inverter, charging them using direct current (DC) power produced by your solar energy from your panels. LG Chem highlights the RESU's compact size, ease of installation, and safety as some of their top selling points. As a dedicated chemicals company, LG Chem has the history and knowledge to back up their claims of quality and safety for their battery products. The new RESU Prime is a large-capacity, high-powered battery line from LG. They rely on newly-developed battery cells with a higher power density than previous batteries from the company, which allows higher overall storage capacities. Customers with RESU Prime batteries have access to LG's RESU monitoring software, which is available as a mobile app. Through this monitoring software, you can see the conditions of your battery in real-time and even proactively alert your installer if something is out of the ordinary.

When you're evaluating solar batteries, you'll want to keep in mind various important metrics and technical specifications. Among the most important are the size of the battery (power and capacity), its chemistry, depth of discharge, and roundtrip efficiency. 

Size

Two of the most important metrics are power and usable capacity. Power (measured in kilowatts, or kW) determines the maximum amount of electricity that a battery can output at a single time, while usable capacity (measured in kilowatt-hours, or kWh) is a measure of the maximum amount of electricity from your battery on a full charge. The LG Chem RESU 10H boasts a maximum power rating of 5.0 kW to go along with 9.3 kWh of usable capacity. 

The RESU Prime comes in two sizes – the RESU 10H Prime and the RESU16H Prime. The RESU Prime boasts a maximum continuous power rating of 7 kW to go along with 16 kWh of usable capacity in their 16H model. In comparison, the 10H model offers 5 kW of maximum power along with 9.6 kWh of storage capacity. The RESU systems are also, to an extent, modular, meaning you can add multiple battery products to your storage setup. You might want to install multiple RESU or RESU Prime batteries for a home with high energy demands, although LG Chem recommends no more than 2 RESU or RESU Prime batteries wired together in parallel.

Think of your battery like water running through a pipe. Energy capacity is the amount of water available to push through the pipe, while power is the size of the pipe itself. Larger pipes allow more water to flow through at once, which depletes the water faster. Similarly, a battery with a high power rating can deliver more electricity at one time but will burn through its available energy capacity faster too.

A battery's power determines what appliances you can run with at once, while usable capacity determines how long those appliances can be run. Batteries with a higher power rating are capable of powering more robust appliances or many appliances at once, while batteries with a higher usable capacity can store more total energy and thus can run your appliances for longer periods of time without needing to recharge.

Basic functionality

The functionality of one solar battery next to another can vary; some batteries have excellent off-grid capabilities, while others offer software solutions for rate arbitrage. Here the important qualities of the LG Chem RESU:

Backup power

LG Chem has made a concerted effort to ensure their battery is compatible with most common brands and types of off-grid and hybrid inverters. This means that as long as your installer installs the correct components, your LG Chem battery will be able to provide backup power for your home when the grid goes down.

Chemistry

The LG Chem RESU is a lithium-ion storage product; specifically, it is a lithium nickel manganese cobalt oxide (NMC) battery. This is one of the most common lithium-ion battery technologies, and for a good reason: relative to other types of batteries, NMC batteries are known for their high energy density (the amount of energy they can store relative to the physical space they take up) and increased safety. To learn more about how different lithium-ion battery chemistries stack up against one another, check out our overview of battery chemistry differences.

The RESU Prime offers the best of both worlds and can provide both excellent off-grid capabilities and software solutions specific to rate arbitrage.

Performance metrics

Two key ways to evaluate the performance of a solar battery are its depth of discharge and roundtrip efficiency. 

Depth of discharge (DoD) indicates the percentage of a battery's energy that has been discharged relative to the overall capacity of the battery. Because the useful life of a battery decreases each time you charge, discharge, and re-charge it, many battery manufacturers specify a maximum DoD level for optimal battery performance. In general, batteries with a higher depth of discharge are considered better quality products. The LG Chem RESU boasts a depth of discharge of 95 percent across all battery sizes, reflective of its safe and advanced NMC battery chemistry. The RESU Prime boasts an excellent depth of discharge of 100%.

Roundtrip efficiency is a measure of electrical losses involved with charging and discharging a battery. The higher the efficiency percentage, the more efficiently the battery is able to convert incoming electricity into stored electricity and then back into usable electricity. The LG Chem RESU line has a high roundtrip efficiency of 94.5 percent; this means that for every 10 kilowatt-hours (kWh) of electricity you put into the battery, you'll receive 9.45 kWh of output. The RESU Prime has a roundtrip efficiency of over 90 percent; this means that for every 10 kilowatt-hours (kWh) of electricity you put into the battery, you'll receive about 9 kWh of output. 

LG Chem RESU performance metrics

LG Chem RESU and RESU Prime model comparison

In most cases, homes with a RESU battery will charge and drain the battery every day. The RESU comes with a 10-year warranty. LG Chem guarantees that the battery will maintain at least 60 percent of its capacity to hold a charge during that time period. LG Chem also offers an energy throughput warranty – the 60 percent retained capacity after ten years is only valid if the total energy throughput over the ten years is less than 22.4 megawatt-hours (MWh). Summed up, your LG Chem RESU battery is warrantied to retain at least 60 percent of its capacity by the time you hit a lifetime of 10 years or an energy throughput of 22.4 MWh, whichever happens first.

LG Chem's battery technology is similar to other rechargeable batteries, both large and small: as time goes on, the battery loses some of its ability to hold a charge. Think of how the battery life of a brand-new smartphone compares to one that is a few years old. As you continually charge and drain your phone's battery, it starts to lose some of its ability to hold a charge.

The battery life of your RESU battery will deteriorate in the same way. That isn't an indicator of a product flaw. All batteries lose some of their ability to hold a charge over time, whether it's an electric vehicle battery, a home energy battery, or a rechargeable AA battery. This is why LG Chem offers a warranty that guarantees a certain amount of storage capacity.

If you want to compare individual battery models side-by-side, our battery Buyer's Guide lets you select products and compare them based on efficiency, capacity, power, and more.

The RESU Prime battery line is backed by a 10-year or 10,000-cycle product and performance warranties that cover the equipment in the case of faulty parts or defects, as well as the actual performance of the battery. LG's warranty coverage says that by the end of 10 years or cycling your battery 10,000 times, your RESU Prime will still be able to store at least 70 percent of its initial out-of-box capacity.

A solar battery installation isn't as simple as a list price for a component – depending on your electrical setup, among other factors, installation costs can vary widely. As a rough estimate, you can expect the LG Chem RESU 10H to cost between $9,500 and $13,000 with a full system installation. That number includes the battery itself, an inverter, various other equipment costs, and estimated installation costs. The LG Chem RESU 16H Prime full system installation cost is estimated to be between $11,000 and $15,000. If you want to install the RESU or RESU Prime as part of a solar-plus-storage system, battery costs are just one part of the equation. A 5 kilowatt (kW) solar energy system costs anywhere from $9,000 to $15,000, depending on where you live and the type of equipment you choose. 

That may sound like a lot of money, but installing a solar-plus-storage system can be a worthwhile investment. Whether or not the LG Chem RESU or RESU Prime makes sense for you is determined by how your electric utility structures its rates and your reasons for installing a solar battery.

In some cases, depending on where you live, you may have access to financial incentives that can reduce your home energy storage installation costs. If you live in California, you could get a cash rebate that covers most of your home battery costs through the Self-Generation Incentive Program (SGIP). Other states (such as Massachusetts) are in the early stages of evaluating battery storage performance incentives as well, and several states already provide cash rebates.

The LG Chem RESU and the RESU Prime are some of the most used batteries today, but whether or not it is worth it depends on your financial situation. It will undoubtedly get the job done of keeping your lights on in a blackout. It is important to know that this can be an expensive battery. It is especially important to consider using a battery to avoid the pitfalls of time-of-use electric rates.

The LG Chem RESU10H battery is currently available through the company's installer network in the U.S. Whether you want to install an LG Chem RESU or other home battery pack, you'll most likely need to work through a certified installer. You can find an installer for a RESU Prime directly through LG's website or from local solar installers and/or installation companies that carry the RESU Prime. Adding energy storage technology to your home is a complicated process that requires electrical expertise, certifications, and knowledge of the best practices required to install a solar-plus-storage system correctly. 

A qualified EnergySage-approved company can give you the best recommendation about the LG Chem home battery system and other energy storage options available to homeowners today. If you are interested in receiving competing installation quotes for solar and energy storage options from local installers near you, simply join the EnergySage Marketplace today and indicate what products you're interested in your profile's preferences section.