The LG Chem Battery: is it right for your home?

Updated

LG Chem’s Residential Energy Storage Unit (RESU) batteries are part of the new generation of solar batteries that provide energy storage and backup power for homes. They are designed to pair with a home solar system and connect directly to a storage-ready solar inverter for charging and discharging.

The LG RESU battery can be installed in either on or off-grid photovoltaic systems, and is one of the leading Tesla Powerwall alternatives. Let’s dig into more about how the LG Battery works and whether it’s right for you.

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    The LG Chem battery for home energy storage

    How the LG Chem battery works

    In a home solar-plus-storage system, one or more LG Chem RESU batteries are connected directly to your solar inverter, charging them using direct current (DC) power produced by your solar panels. 

    The batteries can hold between 7 and 9.8 kilowatt-hours (kWh) of electricity, depending on the size you choose. That corresponds to model # RESU7H for the 7-kWh battery and model # RESU10H for the 9.8-kWh version.

    During the day, when the sun is high in the sky, home solar systems produce more electricity than the house needs. That stored solar energy can be used to power the home later in the evening, after the sun sets. It’s also possible to set the battery to retain a certain amount of its stored energy in case of a power failure.

    Whether you choose the 7 or 10-kWh size, RESU batteries are divided into two sub-models that are each built to communicate with specific brands of solar inverters

    Model numbers with “-C” at the end work with SMA Sunny Boy Storage inverters, and those with “-R” work with Fronius, Huawei, and SolarEdge StorEdge inverters. Your installer will select the proper model to work with your solar system.

    Details about LG Chem RESU batteries

    LG Chem RESU batteries details
    Model name LG Chem RESU7H-R LG Chem RESU7H-C LG Chem RESU10H-R LG Chem RESU10H-C
    Total energy capacity (kWh) 7.0 7.0 9.8 9.8
    Usable energy (kWh) 6.6 6.6 9.3 9.3
    Power rating (continuous) 3.5 kW 3.5 kW 5.0 kW 5.0 kW
    Peak power (10 sec) 5.0 kW 5.0 kW 7.0 kW 7.0 kW
    Voltage range (V) 350~450 430~550 350~450 430~550
    Round trip efficiency 94.5% 94.5% 94.5% 94.5%
    Dimensions (W X H X D, inches) 29.3 x 27.2 x 8.1 29.3 x 35.7 x 8.1 29.3 x 35.7 x 8.1 29.3 x 35.7 x 8.1
    Approximate weight (lb) 168 192 214 220

    Each model has a warranty of 60% capacity after 10 years or 22.4 MWh.

    More information and data sheets available on the LG Energy Storage System site.

    Advantages that set LG batteries apart

    Like all home solar batteries, LG Chem RESU batteries are designed to charge from your solar panels and keep electricity available for you at night and in the case of a power outage. 

    But the LG battery has some specific advantages over other types of batteries.

    LG Chem battery benefits

    • Battery backup for use at night or during a power outage
    • More compact size and lighter weight than competitors like the sonnen eco
    • DC-coupled for greater efficiency and integration with solar storage inverters
    • Easy installation and servicing
    • Can be discharged up to 95% of capacity (depth of discharge)
    • 94.5% round-trip efficiency outputs 9.45 kWh for every 10 kWh stored (exceeds competitor performance)
    • 10-year warranty
    • Available from many solar companies, including Sunrun

    Because they use lithium ion batteries, LG battery packs can be discharged to almost their full capacity every day, and last a long time. On average, LG Chem battery systems can charge and discharge every day for 10 years and still retain 60% of their original capacity.

    In addition, LG’s advanced manufacturing process produces batteries that are more compact, more efficient, and lighter than many alternatives. And the LG Chem RESU batteries are all DC-coupled, meaning they charge directly from solar panels, which is more efficient than charging from power that has been converted to AC before reaching the battery.

    Finally, the LG Chem RESU battery is available from many different solar installers across the country, including Sunrun, which sells the LG batteries for a low monthly payment as a managed energy storage solution they call “Brightbox.”

    The LG Chem battery warranty

    LG Chem’s warranty promises that its RESU batteries will maintain at least 60% of their initial rated energy storage capacity after 10 years OR before the battery has been used to provide 22.4 megawatt-hours (MWh) of electricity.

    That distinction is important, because if you’re fully charging and discharging the battery daily, you’ll run through that amount of MWh sooner than 10 years. To spread 22.4 MWh over 10 years, you’d have to ensure the batteries discharge an average of only 6.14 kilowatt-hours (kWh) per day, which is 62% of their capacity.

    This should be fine for most people, as daily cycling of the battery isn’t necessarily the plan. Talk to a licensed installer to find out whether you should expect to use more than 6.14 kWh of battery storage per day.

    The warranty doesn’t include explicit protections from defects in materials and equipment, which is a fairly major oversight. The warranty implies that LG will repair or replace the battery if it’s found to be defective, but that doesn’t meet a very high standard. 

    It would be better if LG explicitly guaranteed protection for faults in materials and workmanship for 10 years.

    Cost and incentives

    Like many other solar system components, the price of the LG RESU batteries changes over time, and depends on where you install it and who does the work. 

    As of January 2021, it costs between $5,000 and $7,000 to buy a RESU10H battery, before installation costs. If you include installation costs from a solar installer, a RESU 10H might cost between $7,000-$9,000.

    That’s not cheap. Luckily, there are solar battery incentives that can help bring down the costs. 

    Because the LG Chem batteries charge exclusively from solar panels, they qualify for the federal solar tax credit, reducing your total cost to purchase the battery by 26%, down to between $5,200 - $6,700 after the first year.

    Some states and utility companies also offer solar battery incentives. The most popular is the Self- Generation Incentive Program (SGIP) in California. 

    Is the LG Chem RESU battery worth it?

    Whether battery storage is worth it to you depends on the price you put on peace of mind. 

    If you absolutely cannot bear the thought of suffering through a blackout in the dark, then the LG battery is an excellent choice. And, with Californians now seeing “planned outages” of more than a day or two on a regular basis, it might prove its worth in short order.

    The only way the LG battery becomes financially worth it is if you use it to avoid time-of-use or demand charges. In that case, you’d have to be saving over $.50/kWh on every kWh of storage in order to make it worth it over the 10-year lifespan of the battery.

    No place on earth has a difference of $.50 between its on- and off-peak electric rates, so the cost of the LG battery will basically never be repaid.

    However, if you look at this more like a balancing act, between the “peace of mind” benefits and the tangible financial benefits, it might start to look better. Especially if you live in California.

    How much can you save by going solar?

    Key takeaways

    • The LG Chem RESU battery is one of the most popular home batteries available.
    • One LG RESU battery can hold between 7 and 10 kilowatt-hours, based on the model (enough for about a third of your home’s daily needs).
    • If installed alongside a solar installation, the battery qualifies for the federal solar tax credit, and some state incentives also exist.
     - Author of Solar Reviews

    Ben Zientara

    Solar Policy Analyst and Researcher

    Ben is a writer, researcher, and data analysis expert who has worked for clients in the sustainability, public administration, and clean energy sectors.

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