Photo courtesy of Panasonic Eco Systems
As energy prices rise and power outages become more common, solar battery storage systems are gaining popularity. By storing electricity for homeowners to use later, batteries reduce reliance on the grid, providing backup power during blackouts and a source of electricity when utility rates rise. However, not all batteries are the same, and choosing the right one for your home requires careful consideration. Here's a detailed breakdown of the key factors to evaluate when choosing between home batteries.
What are the benefits of solar batteries?
Battery energy storage systems give homeowners more control and independence over their energy usage and costs. By storing power to use later, home batteries provide a source of round-the-clock electricity that homeowners can tap into during an outage or when grid electricity rates rise.
For homes with solar panels, the benefits of batteries go even further by enabling you to store your free, clean solar power when no one is home to use it. You can then tap into it when you return home or when the sun goes down and your panels stop generating. If you're on a time-of-use rate plan with your utility, you can use your stored power during times of peak demand to avoid paying higher prices.
10 factors to consider when evaluating home solar batteries
#1 AC vs DC-coupled batteries
Choosing between an AC- or DC-coupled system is one of your first decisions. These terms refer to how a battery connects to solar panels. The type you choose largely depends on whether you're adding a battery to an existing solar array or whether you plan to install solar in the future.
AC-coupled batteries are often the best choice if you already have solar panels, as they are easier to install onto existing arrays. On the other hand, if you're installing solar at the same time as a battery or in the future, then a DC-coupled system can be a better option. They're usually more efficient and have fewer components, reducing the potential points of failure and lowering installation costs.
Panasonic's EVERVOLT® solar battery uses a hybrid inverter. This means it can pair with new solar panels in a DC-coupled system or integrate into existing solar systems using AC-coupling.
EVERVOLT solar battery system, photo courtesy of Panasonic Eco Systems
#2 Capacity and power output
These are two of the most important technical specifications to consider when choosing between batteries. The capacity is the total amount of energy a battery can store in kilowatt-hours (kWh). The power output is the maximum amount of electricity it can supply at a given time, in kilowatts (kW).
In practice, this means that a solar battery with a 10kWh capacity can theoretically supply 1kW of power for 10 hours. If it has a power output of 5kW, at any given moment, it can supply up to 5kW of power. Therefore, if you're running several appliances that together use 5kW of power, the battery would last for about 2 hours before being fully discharged.
An installer will analyze your energy bills and usage patterns to determine the optimal capacity and power output for your household's energy needs. George Mirza, a solar and energy storage product solutions engineer at Panasonic Eco Systems, recommends looking for a battery with a power output of between 11.5 and 13kW and a capacity of 30kWh. (This spec is for a full battery system, not just a single inverter and applies to a typical home. System size may change based on actual site needs.)
#3 Grid-tied or independent
If you want to use your solar battery during an outage, you need to confirm this with your installer to ensure it's configured for this function, Mirza explains. Some batteries only operate when connected to the grid (grid-tied), which means they can't provide power when the grid goes down. The Panasonic EVERVOLT can be installed for either on-grid usage or backup power, which means it will keep running during an outage.
#4 Scalability
Mirza shares a common misconception that one battery can store enough electricity to power your entire home. Most batteries are not large enough for this. Instead, most homeowners install a single battery and then select which appliances and systems are the most important to keep running, such as the refrigerator, lights, and Wi-Fi.
For homeowners who want to meet more of their energy needs, there is the option to install additional batteries. Systems such as the EVERVOLT are modular, which means you have the option to stack them and expand your storage capacity if your home energy requirements increase.
#5 Roundtrip efficiency
The efficiency of a battery refers to how much of the stored energy can actually be used when the battery is turned on. It's often referred to as 'roundtrip efficiency' and is displayed as a percentage. The higher the percentage, the more energy is converted into power you can use in your home, meaning less waste and better overall performance.
"Even just a two to three percent difference in roundtrip efficiency is going to add up to a pretty significant change to your energy bill over time," says Mirza. For example, a battery like the EVERVOLT has a 94% roundtrip efficiency, meaning if you store 10kWh of electricity, you can use 9.4kWh in your home. If the efficiency was 90%, 9kWh could be used in the home.
#6 Installation location
Manufacturers specify where their solar batteries can be installed. Some can be installed indoors, while others can be mounted onto walls, while some must stay on the ground. Be sure to check where a battery can be located before making a decision. If you don't follow the manufacturer’s instructions, you risk voiding the warranty.
"Double check the typical temperature range where you're looking to install a battery," notes Mirza. Like all electrical equipment, batteries' performance can be negatively affected by extreme heat and cold. "Most batteries are certified for installation outdoors, so if you want to install one inside, you need to check it's certified for this." The EVERVOLT is versatile in that it can be installed indoors and outdoors, wall-mounted or floor-mounted.
EVERVOLT solar battery storage system, photo courtesy of Panasonic Eco Systems and Connected Solutions
#7 Warranties
Batteries are designed to work for a decade or more, and once installed, failures are pretty rare. Nevertheless, batteries are expensive, so it's important to ensure you have good warranties that will ensure your system runs smoothly.
Batteries should come with three warranties covering the product, performance and labor, explains Mirza. He recommends looking for a warranty of 10 to 15 years for the product, performance and labor. "Warranties don't always cover labor but the EVERVOLT warranty does," he adds. "Make sure you choose a reputable manufacturer, who provides proper troubleshooting and support for you and your battery installer."
#8 Solar battery cycles and lifespan
When you charge your battery and then use the energy it stores, you put it through a 'cycle.' A battery's lifespan is measured in the number of cycles it can go through before its performance declines. This is known as 'cycle life', and manufacturers typically guarantee a maximum number of cycles before the battery reaches the end of its warranty period. For example, the EVERVOLT has a cycle life of 6,000 over 12 years, which means it can be charged and discharged about 500 times per year while remaining within its warranty coverage.
#9 Costs and incentives
Solar batteries cost about $9,400 to install on average after deducting the federal tax credit, which knocks 30% of the total installation costs off your federal tax bill. There's no limit to the amount you can claim, and there are also no income limits for claiming the credit.
You may also be eligible for other local incentives and rebates, such as those from your state or utility company, that you can use in combination with the federal tax credit to further lower your costs. Massachusetts, for instance, offers its own tax credit that allows homeowners to deduct 15% of installation costs from their state tax bill.
#10 Monitoring
Most batteries come with an app for monitoring household energy data, such as your usage and the amount of power stored in your battery. But some apps go further, enabling you to optimize energy usage throughout the home intelligently.
Panasonic's EVERVOLT SmartBox, for example, can manage many your home energy systems, including your battery, solar panels (if you have them), and selected critical appliances that you wish to be intelligently managed by the SmartBox. This means it can automatically adjust to conserve power and keep your home comfortable. It can also prioritize devices based on your preferences and even make quick decisions on your behalf, such as when to store and supply power from your battery based on electricity costs.
With so many different solar batteries to choose from, it can be challenging to know where to start. The first step is to choose a reputable and experienced installer who will work with you to determine the best battery to meet your energy needs and budget. When you’re ready to take the first step, get your questions answered by your local Panasonic Authorized Installer with a free consultation and quote.
