6 Best Solar Batteries
Solar panels convert sunlight to electricity, and batteries store it. Solar battery technology is still evolving, but here's what's available today.
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Buying a Solar Battery?
The passage of the Inflation Reduction Act in August 2022 provides government assistance for homeowners who install solar systems, so there’s no time like the present to learn about and shop for solar batteries.
Or perhaps you have an existing system with old batteries that need to be upgraded. Either way, you want to make an informed choice.
Solar properties not tied to the power grid need battery storage to provide electricity when the sun isn’t out. Grid-tied properties don’t necessarily need battery storage, but it’s a good idea because it provides a backup plan during power outages. When used wisely, it can help lower energy bills.
The introduction of the Tesla Powerwall, a stylish, self-enclosed electricity storage system that hangs on a wall, advanced solar battery technology. Today’s solar batteries, incorporating lithium-ion technology, are cleaner and more efficient than the lead-acid ones of the recent past. Many of the newer solar batteries feature integrated system components, such as inverters and charge controllers, which greatly simplify installation.
A solar battery is a big investment, so it’s important to do your homework. Compared to 2015, when Tesla began marketing the Powerwall in earnest, there are a lot of options. Consider these things when shopping:
- Safety: Of the two predominant lithium storage technologies, lithium iron phosphate (LFP) is safer. Batteries using lithium nickel manganese cobalt oxide (NMC) need good ventilation because they run warmer and shouldn’t be placed inside the home. If you want to put the battery in the basement, choose an LFP.
- Capacity: Generally a measure of how much energy a battery stores, it’s one of the factors that determine how long the battery lasts before needing to be recharged. It’s measured in kilowatt-hours (kWh).
- Power: Measured in kW, this is another factor that determines how long a battery will last. Some batteries have an instantaneous power rating as well as a continuous one. You’ll need high instantaneous power to run a device like a sump pump or well pump that cycles on and off frequently.
- Depth of discharge (DoD): This measures how much of the stored energy is usable. The minimum DoD for a solar battery is around 90 percent, but many approach 100 percent. That means they can be completely discharged without damage.
- Round trip efficiency: Similar to DoD, this measures how much energy the internal processes of the battery consume.
- Lifespan: Battery longevity is commonly measured by the number of charging cycles it can undergo and still perform at an acceptable level. Most solar batteries are good for 3,000 to 5,000 cycles, but more expensive ones may last for as many as 10,000 cycles. Warranty periods are usually specified in years (10 years is standard) and cycles.
- System compatibility: Some batteries only work with equipment manufactured by the same company, while others can be added to an existing system.
- Modular: Some solar battery systems are stackable so you can size the storage according to your needs. Some aren’t.
- Cost: Price is always a consideration, but it’s tied to many variables. You wouldn’t choose a solar battery based on cost alone.
The Luna2000 from Huawei features five kWh modules that can be seamlessly stacked together to make a five, 10 or 15 kWh system. The batteries employ clean LFP technology and an internal heating system to perform better in cold climates.
Each battery module has 100 percent DoD and generates 2.5 kW of continuous energy and 3.5 kW of peak (instantaneous) energy. The inverter, which has the same sleek style as the battery modules, is sold separately. It connects easily to the battery bank and to the home’s electrical panel.
German manufacturer sonnenBatterie released the sonnenCore+ to consumers in 2022. It uses LFP technology, and the company says the sonnenCore+ is 100 percent recyclable.
This battery comes in two sizes: 10 kWh and 20 kWh. Each comes with an integrated inverter for seamless connection to the electrical panel. It also comes with a 10-year or 10,000 cycle warranty, which is up there with the best of them. The 10 kWh model has a power rating of 4.8 kW, a 100 percent DoD and a round-trip efficiency of 85 percent.
Available only by consultation through the company’s website, the Tesla Powerwall is an integrated system that includes battery storage, inverter and WiFi functionality. You can interact with it via your mobile device or laptop.
The Powerwall has a power rating of five kW, but units can be stacked to supply up to 35 kW. Its smart technology makes the Powerwall suited primarily for grid-tied systems. Because it employs energy-dense NMC technology, it needs to be in the garage or an outbuilding. It comes with a 10-year or 10,000-cycle warranty.
The Generac PWRcell is a modular battery that comes with a minimum of three cells with a storage capacity of nine kWh. It can be upgraded to increase storage capacity to 18 kWh. This battery must be installed at the same time as the panels; it can’t be tied in afterward.
The PWRcell comes with an external inverter and automatic transfer switch. The weatherproof cover means it can be safely installed outside.
Unlike the other batteries on this list, the Sunrun Brightbox is available only to homeowners who also purchase panels from the company. This battery is part of the LG Chem RESU series. LG exited the solar industry in 2022, leaving Sunrun as the exclusive distributor.
The Brightbox compares favorably to the Tesla Powerwall, although at 9.3 kWh it has slightly less power. It has enough capacity to keep things running for at least 10 hours during a power outage. Because the company delivers the entire package, a consultation is necessary to determine system size and configuration.
Enphase IQ Battery 10
The Enphase IQ Battery 10 incorporates three smaller batteries (IQ Battery 3) for a continuous power rating of 3.84 kW and a peak power rating of 5.7 kW. The battery features 10.08 kWh capacity.
This battery is lighter than most others on the list and incorporates LFP chemistry and 12 embedded micro-inverters for seamless connection to the electrical panel. It has a round-trip efficiency of 89 percent. One drawback is the warranty period, limited to 10 years or 4,000 cycles — fewer cycles than other batteries in its class.