Your solar energy system will likely be designed to produce enough energy to meet your annual electricity needs. But most likely, you won’t need all the energy your system generates, especially during the middle of the day when production is high, but your power consumption is low. So what to do with all that excess energy? It's simple: solar batteries can store the surplus energy and power your home with it once the sun sets, reducing or even eliminating your need for grid power overnight.

When designing your system, your installer can ensure you have enough battery storage capacity—and panels to charge them—to get you through the longest winter nights. When the sun rises, your solar will start to power your home again, and recharge the batteries with any excess production. If your system is tied to the grid (the vast majority are), any extra energy produced after your battery is full can feed back into the utility grid, often earning you bill credits under net energy metering programs. (Depending on your net metering export rates, it might be better to program your battery to export surplus energy to the grid rather than charging your battery, especially during peak hours when you get a higher credit for that energy.)

Many states and utilities also offer incentives to lower the cost of including batteries with your solar energy system. Incentives are often on a per-kWh basis (a set amount of money for each kWh of storage; so, for instance, if you have a 10 kWh battery and the incentive is $200/kWh, your incentive or rebate would be $2,000). Some states offer higher rebates for lower-income households to give wider access to money-saving clean energy.

Plus, batteries are often eligible for the 30% federal tax credit in the Inflation Reduction Act, further reducing battery costs.

Having solar with batteries can enhance your energy independence, save you even more money, and, if configured for backup, help protect you against outages in your area.

Batteries can be installed outside (Enphase IQ Batteries, for example, are fully weather-resistant), or in a garage or basement. Your solar installer will help determine the best location for your batteries.

Learn more about investing in solar batteries

There are several types of batteries that your solar can charge and use for supplemental or backup power.

AC-coupled

AC-coupled batteries like the Enphase IQ Battery 5P can accept AC current. Working in conjunction with the Enphase IQ8 Microinverters on your solar panels, energy is converted from DC to AC at each panel and then fed to your house to power daily needs and charge the battery. The IQ Battery 5P has built-in microinverters that convert the AC back to DC for storage since AC can’t be stored. When you draw energy from the battery to power your home, the microinverters convert the DC back to AC for your home to use. AC-coupled batteries tend to be easier to install with existing solar systems, as well as new ones.

DC-coupled

DC-coupled batteries like the Tesla Powerwall 3, SolarEdge, and LG Chem work a bit differently. They’re more commonly used with solar systems that employ string inverters. Panels generate DC electricity, some of which is fed into a central string inverter and converted to AC for your home, while some of the DC is fed directly into your battery to store. When you draw energy out to your home, the DC runs out of the battery through the same string inverter your panels use to convert DC into usable AC electricity. However, as noted earlier, these systems have a single point of failure—if the central inverter goes down, so do the panels and batteries. These batteries can be less expensive, but there’s a reliability risk because of this single point of failure.

Portable batteries

These are compact options (up to 4 kWh) for critical backup needs like lights, refrigerators, and Wi-Fi. Portable units typically feature 120 V outlets and can recharge from solar panels or the grid. Companies like Goal Zero and Ecoflow are two of the more popular portable battery providers, and the new Enphase IQ PowerPack 1500 has brought new levels of performance and reliability to the market.

If you’re a California homeowner—especially under NEM 3.0 with its low bill credit rate—backup batteries can help lower your yearly "true-up" bill from your utility at the end of the 12-month solar billing cycle. Your true-up tabulates how much electricity your home drew from the grid for the year and the retail rate for that usage based on the time of day (for time-of-use rate plans) while also applying any bill credits you earned selling your excess power back to the grid. If you use more electricity than your solar system produces, you’ll have a bill to pay at the end of the year.

Batteries help because you can set them up to power your home during peak rate periods—usually late afternoon and through the evening—instead of drawing grid power. This will reduce the overall amount of grid power you use annually and do it during the most expensive times of the day.

In addition, you can program your battery to send power back into the grid when export rates (the rate your utility pays for power sent to the grid from your battery) are higher, so you get a higher credit for that energy. (Also usually during peak rate periods.)

This strategy can help offset energy costs by reducing your dependence on expensive grid power.

Grid outages—whether caused by extreme weather, fire-prevention shutoffs, or system overloads—remain the prime reason people include batteries configured for backup in their solar energy system. If the grid goes down during the day, solar will continue to power your home and charge your backup battery until nightfall. Then the battery can power your home until sunrise or the grid comes back online.

With a smart Enphase Energy System, even if your battery nears empty overnight, your solar panel will still work when the sun rises again. Along with powering your home, solar will also start charging your battery when production exceeds the power your home is drawing.

There are two primary chemistries available today:

Lithium nickel manganese cobalt oxide (NMC)

NMC batteries like Tesla’s Powerwall 1 and 2 tend to have higher energy density than LFP but also a bit less longevity—1,000 to 2,000 charge/discharge cycles.

Lithium iron phosphate (LFP)

LFP batteries have a longer lifespan—3,000 or more charge/discharge cycles—and are safer because of their more stable battery chemistry.

Enphase IQ Batteries use LFP chemistry and operate with low-voltage AC power, which avoids the risks associated with high-voltage DC power. Enphase backs its batteries with a 15-year limited warranty covering up to 6,000 charge/discharge cycles. IQ Batteries are also the first microinverter-based storage system to meet the UL 9540A safety standard—a test for protection against the spread of runaway fire for indoor battery storage systems. It means you can safely install them inside, and install more of them in a smaller space, too.

Learn more about battery chemistry and safety

There are a few questions you should ask yourself when deciding whether to add batteries to your solar energy system, whether it's an existing system or a new one you're installing.

Will the savings from the battery justify the investment? There are many factors to consider when calculating potential savings. First, take the upfront cost minus any tax credits and incentives, then calculate how much you’ll save by storing excess solar production and using it to power your home after sunset—often the time with the highest per-kWh electricity rate. Don't worry. An Enphase installer can help calculate this for you.

Do you need backup power? Batteries provide backup during outages, which is particularly valuable if you live in areas prone to severe weather, wildfires, or your utility experiences frequent outages.

Do you have space to install batteries? Batteries like the Enphase IQ Battery 5P are compact and rated for indoor or outdoor use, so you can install them where it works best for you.

Put simply, the combination of savings and peace of mind offers a strong argument for including or adding batteries to just about every system.

If you want battery storage for your solar system, you just need to find the right battery and decide how much storage you need.

Your installer can figure out how much energy you use, what your essential loads are—like lights, refrigerator, and Wi-Fi—and how much energy they use daily to determine storage capacity needs. They can also recommend the best place to install the batteries and address any safety concerns you may have. This should help you get the right amount of storage and the best type of battery for your home.

Learn more through our essential guide to home solar batteries