LG is one of the biggest names in energy storage. Their original battery, the RESU, is one of the most popular models in the industry. Now, their newest model–RESU Prime–is out; it’s 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 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.
How does the RESU Prime work?
The RESU Prime pairs well with solar panel systems, especially if your utility has reduced or removed net metering, introduced time-of-use rates, or instituted demand charges for residential electricity consumers. Installing a storage solution like the RESU Prime with a solar energy system allows you to maintain a sustained power supply during both day and night, as long as you store enough power from your solar panels when the sun is shining.
As with many other home battery products, the RESU Prime is sized for day-to-day use at your home and is primarily designed to be paired with a 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 stored energy in your battery instead of having to buy it from your utility company.
Key things to know about the RESU Prime
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. The RESU Prime is a modular battery system, meaning you can stack multiple batteries together to create a larger storage system. Specifically, you can combine up to 2 RESU Primes for a bigger setup.
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 evaluating the RESU Prime, there are various important metrics and technical specifications to keep in mind. Among the most important are the size of the battery (power and capacity), its depth of discharge, and roundtrip efficiency.
The RESU Prime comes in two sizes – the RESU10H Prime and the RESU16H Prime. Two important metrics to keep in mind when comparing the RESU Prime options to other home batteries are power and usable capacity. Power (measured in kilowatts, or kW) determines the maximum amount of electricity that can be output at a single time, while usable capacity (measured in kilowatt-hours, or kWh) is a measure of the maximum amount of electricity stored in your battery on a full charge. 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, while the 10H model offers 5 kW of maximum power along with 9.6 kWh of storage capacity.
Think of your battery like water running through a pipe. The usable 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 stored energy faster too.
A battery’s power determines the number of appliances you can run from the battery concurrently, while usable capacity determines how long those appliances can be run. Batteries with a higher power rating are capable of powering more, bigger appliances (i.e., your HVAC system) 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.
The functionality of one solar battery next to another can vary; some batteries have excellent off-grid capabilities, while others offer software solutions specific to rate arbitrage. The RESU Prime offers the best of both worlds, and can provide both of these services.
Two key ways to evaluate the performance of a solar battery are its roundtrip efficiency and depth of discharge.
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 RESU Prime has a roundtrip efficiency of over 90 percent (a significant improvement from previous batteries!); this means that for every 10 kilowatt-hours (kWh) of electricity you put into the battery, you’ll receive about 9 kWh of output.
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–or cycle–your battery, 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 RESU Prime boasts an excellent depth of discharge of 100%.
RESU Prime warranty coverage
RESU Prime warranties
- Warranty period: 10 years
- Guaranteed end of warranty capacity: 70%
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.
Importantly, LG’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 Prime 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 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.
How much does the RESU Prime cost?
The cost of installing a battery isn’t as straightforward as looking up the list price for an individual component–i.e., your battery. In fact, depending on your electrical setup, installation costs can vary widely. Unfortunately, LG does not release MSRPs for their solar and storage products, so we don’t have a cost quite yet.
In some cases,, you may have access to financial incentives that can reduce your home energy storage installation costs. For instance, 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.
Can you go off-grid with the RESU Prime?
Installing a solar-plus-storage system at your home is a great way to take control of your electricity bill, but it doesn’t mean that you’re completely disconnected from your utility. Going “off the grid” with solar batteries is actually a more expensive and complicated proposition than you might think. Most home batteries, including the RESU Prime, only have enough capacity to store electricity for hours, not days at a time. If you want to make sure you can maintain power to your property for days, you’ll need to install several RESU Prime batteries together to increase your storage capabilities.
Where to buy the RESU Prime
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 needs 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 RESU Prime 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 Solar Marketplace today and indicate what products you’re interested in your profile’s preferences section.