How Long Can Solar Battery Power a House During an Outage?
When you install a home battery, what you are really doing is providing your home with a backup energy reserve in the case of an outage.
Whether you have a solar panel system at your home or not, a home battery can be used to store electricity and deliver it to your home appliances and devices. The benefits of a home battery are clear, especially during short or long-term outages, or in areas with Time-of-Use (TOU) rates that make electricity more expensive during peak use hours.
In this article, we’ll show you how to calculate how long a battery paired with solar can power your house during a power outage, and give you some tips for maximizing your battery usage.
How long can a solar battery power a house?
Without running AC or electric heat, a 10 kWh battery alone can power the basic operations of a house for at least 24 hours, and longer with careful budgeting. When paired with solar, battery storage can power more electrical systems and provide backup electricity for even longer.
In fact, a recent study by the Lawrence Berkeley National Laboratory found that when heating and cooling are excluded:
“(A) small PVESS with just 10 kWh of storage (at the lower end of sizes currently observed in the market) can fully meet backup needs over a 3-day outage in virtually all U.S. counties and any month of the year.”
PVESS stands for photovoltaics and energy storage system.
But exactly how long you can power your home with solar battery storage varies for each home and depends on three main things:
- Your battery storage capacity
- The output of your solar system
- Your electricity needs during an outage
We’ll show you how to budget your electricity to meet your solar and battery capacity below. First, let’s start with identifying your battery storage capacity.
Home battery capacity
Capacity — the amount of energy a battery can story — is one of the main features that influence how long a battery can power a house during a power outage.
Battery storage capacity is measured in kilowatt hours (kWh) and can vary from as little as 1 kWh to over 10 kWh. Multiple batteries can be combined together to add even more capacity, but a 10 kWh home battery is typical for most homes.
Check out this video to know more about Kilowatt hours (kWh).
During a power outage, assuming you have a fully charged home battery, you will be able to use most of the 10 kWh of stored energy. You’ll want to leave a minimum charge of 5-10% on your battery for a couple main reasons:
- To maintain the health of your battery
- To start your solar inverters in the morning so you can recharge your battery with solar power
For a 10 kWh battery, you’ll want to leave at least 0.5 kWh of capacity in reserve at all times. That leaves you with 9.5 kWh to power your home during a power outage.
On it’s own, 9.5 kWh of battery storage can power essential electrical systems for a day or two. But central air conditioning uses around 3 kWh per hour, which would eat up the entire battery in just over three hours. Let’s see pairing battery with solar can expand your options during a power outage.
Solar system output
The beauty of pairing battery storage with solar is that you essentially create your own miniature utility to power your home. This is especially useful during prolonged power outages because unless you have battery storage, your solar system will be turned off by the local utility to prevent the backflow of electricity from injuring workers trying to repair the grid.
But if you have battery storage, your system can operate independently when the grid is down. This is called “islanding.”
How electricity does a solar system produce?
Solar panel systems are measured in kilowatts (kW) that represent the amount of energy the system can produce in an hour of peak sunlight. So a 5 kW solar system can produce 5 kWh of electricity per hour in ideal conditions. But since conditions aren’t always ideal, we typically assume a performance ratio of 75%.
The average number of peak sunlight hours per day varies from 3.5 to 5.5 in the US. Multiple the system capacity by sunlight hours and 0.75 to find the daily output of a solar system.
For example, here’s how you would find the daily output of a 5 kW solar system getting 4.5 peak sunlight hours per day equals:
5 kW solar system x 4.5 sunlight hours per day x 0.75 performance rating = 16.875 kWh per day
In many cases, that’s more than enough to power essential electrical systems and recharge a 10 kW battery to use overnight. But electricity needs vary from home to home, so let’s run through a some common appliances and how much energy they use.
Your electricity needs during a power outage
How long solar battery storage can run your home depends how much electricity you use. And how much electricity you use depends on which appliances and systems you’re running.
During a power outage, it’s recommended to budget electricity for the most necessary things first and then make a plan for the remainder capacity. For many homeowners, the list of priorities includes:
- Refrigerator
- Kitchen and cooking
- Water heating
- Lights
- TV and device charging
- Heating and cooling
Now, heating and cooling is last on the list not because it isn’t important, but because these operations take so much electricity they’ll likely have to be limited regardless of your battery capacity. So the wise move here is to budget your essentials first, and then get a sense of how much battery capacity is left for heating and cooling.
Note: If you have a gas furnace, you won’t need much electricity to keep the heat on.
Let’s run through an example scenario of powering essential systems during a 24-hour power outage to get an idea of how much solar and battery capacity you’ll need.
Use the tables below as an a la carte menu to create your own battery storage budget.
Refrigerator: 1.5 kWh per day
| Model | Energy use |
| “>Older 15-cubic foot unit (1996) | “>5 kWh per day |
| “>Newer ENERGY STAR 17-cubic foot unit | “>1.16 kWh per day |
A refrigerator is among most important things to power during an outage so that you can avoid having your food and drink go to waste.
If you have a modern, energy star approved model, your refrigerator is using around 1-2 kWh of electricity a day. If your fridge lived through Y2K, you might be looking at closer to 5 kWh per day.
Refrigerator electricity usage can be minimized by opening the door less and raising the temperature slightly. If you are preparing for a planned Public Safety Power Shutoff (PSPS), set the temperature very low before the shutoff event, and then set it to a higher temperature once the grid power goes out. That way the fridge starts cold and you can devote less battery capacity to power it during the outage.
Let’s say you have a relatively modern ENERGY STAR certified fridge that uses 1.5 kWh per day.
Running total: 1.5 kWh
Kitchen and cooking: 1 kWh per day
| Appliance | Energy use |
| “>Electric oven | “>2.3 kWh per hour |
| “>Oven: surface | “>1.1.5 kWh per hour |
| “>Microwave oven | “>0.12 kWh per 5 minutes |
| “>Coffee maker | “> |
Even during a power outage, people gotta eat. And in a large enough outage, it may not be practical to eat out or order delivery.
Let’s say you make a pot of coffee and toast in the morning (0.2 kWh), microwaved some leftovers for lunch (.12 kWh), and baked a frozen pizza for dinner (0.75 kWh) because your trying to clear out the freezer. That amounts to just over 1 kWh throughout the day.
Running total: 2.5 kWh
Electric water heating: 2.5 kWh a day
| Appliance | Energy use |
| “>Electric water heater | “>4-5 kWh per day (running 2-3 hours) |
| “>Heat pump water heater (50-75 gallon) | “>~2.5 kWh per day |
Water heating accounts for an average of 18% of the total energy used in the household. or around 162 kWh per month. On a normal day, a water heater runs for around 2 to 3 hours a day, which means that it will consume roughly 4-5 kWh of electricity a day. Heat pump water heaters are more efficient and can run on around 2.5 kWh per day.
But power outages are not normal days. To save electricity, you may want to skip or shorten your shower, wash your hands and rise your dishes with cold water, and hold off on laundry for a day or two.
And if you have a gas-powered water heater, water heating is a non-issue in terms of battery use.
But for the sake of argument, let’s say you put on some extra deodorant and limit your water heating use to 2.5 kWh per day.
Running total: 5 kWh
Lights: 1 kWh per day
| Bulb type | Energy use |
| CFL/LED (8 W) equivalent to 25 W incandescent | 0.008 kWh per hour |
| CFL/LED (15 W) equivalent to 60 W incandescent | 0.015 kWh per hour |
| CFL/LED (27 W) equivalent to 100 W incandescent | 0.027 kWh per hour |
| CFL/LED (38 W) equivalent to 150 W incandescent | 0.038 kWh per hour |
Compared to larger appliances, lights require very little electricity, especially if you have compact fluorescent (CFL) or LED bulbs. Even at the high end, a 38W LED bulb or 150 W incandescent bulb uses just 0.038 kWh per hour.
So if you budget 1 kWh of battery storage per day to lighting, you could run 26 bulbs for 1 hour each — more than enough to provide light for trips to the bathroom, closet, and getting ready for bed.
Remaining battery budget: 6 kWh
TV and device charging: 2 kWh
| Device | Energy use |
| Wi-Fi router | 0.024 kWh per day |
| “>Modern TV: LED/OLED 4k or 1080P HDTV (20″ to 70″) | “>0.014 to 0.18 kWh per hour |
| “>TV: Plasma (40″ to 50″) | “>0.4 to 0.48 kWh per hour |
| “>Desktop computer | “>0.06 kWh per hour |
| “>Laptop computer | “>0.02-0.05 kWh per hour |
| “>Tablet | “>0.032 kWh per day |
Let’s be honest, one of the worst parts of power outages is going without internet and TV. Sure, you try to read a book for an hour or two, but that familiar glow is calling your name.
To keep the Wi-Fi on, you’ll need about 0.024 kWh. If you work from home, you can run your laptop for 8 hours for another 0.4 kWh. And if you want to wind-down with a movie or 3-hour Netflix binge, you’ll need another 0.54 kWh.
That adds up to 1.18 kWh, but we’ll round up to 2 kWh to account for phone charging and multiple devices running at once.
Remaining battery budget: 8 kWh
Air Heating and Cooling: Variable
| Appliance | Energy use |
| “>Heating | |
| “>Electric furnace (with fan) | “>10.5 kWh per hour |
| “>Portable heater | “>1.5 kWh per hour |
| “>Baseboard heater (6-foot unit) | “>1.5 kWh per hour |
| Cooling | |
| “>Window/Wall AC (8k to 18k BTU) | “>0.73 to 1.8 kWh per hour |
| “>Central AC (3 ton – 12 SEER) | “>3.0 kWh per hour |
| “>Pedestal fan | “>0.03 kWh per hour |
| “>Ceiling fan | “>0.025-0.075 kWh per hour |
As you can see from the table, heating and cooling take a lot of electricity. So if you only had a 10 kWh battery and no solar, you’d have maybe 2 kWh to budget for running fans or space heaters.
But with a battery charged by solar, you would have much more electricity to spare for fans and space heaters — perhaps even enough to run central AC for a few hours, depending on your equipment.
Medical equipment
| Device | Energy use |
| “>Nebulizer | “>1 kWh per hour |
| “>Oxygen concentrator | “>0.46 kWh per hour |
| “>Sleep apnea machine (CPAP) | “>0.2 kWh per hour |
Another thing to consider is powering medical equipment during a power outage. Certain equipment, like a nebulizer, requires a significant amount of electricity and could eat through 10kWh of battery very quickly.
Is getting a solar battery worth it?
Weather-related power outages in the US increased roughly 78% from 2011 to 2021, and are becoming a reality for more homeowners. If you like clean, quiet, and hands-free backup energy that can power your home for several days during outages, then solar and battery are totally worth it. Not only can battery keep your home powered, it can keep your local grid running, as we saw in California in September 2022.
In addition to providing backup power during outages, solar and battery can reduce your energy costs by shifting your power usage to off-peak hours when electricity is much cheaper (up to 20 cents per kWh!)
And, of course, there are the local and global impacts of reducing fossil fuel that pollute the air and contribute to climate change.
Click here or enter your zipcode above to see how much you can save with solar and battery.
Solar batteries: Are they worth the cost?
If you’ve been looking to install a solar panel system recently, you’ve probably come across the topic of solar batteries. Although battery systems are becoming increasingly popular, many homeowners still don’t know much about them.
Solar batteries let you store the energy your solar panels produce for later use. Pairing your solar panels with solar batteries to create what is known as a ‘hybrid solar system’ comes with a number of advantages, including access to reliable backup power and independence from your utility.
But how exactly do solar batteries work? And more importantly, how much do they cost? Keep reading to find out.
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Calculate how much it will cost to install solar-plus-battery-storage for your specific home
How solar batteries work
Solar batteries store the extra solar energy your panels produce that you don’t immediately use so that you can draw from it later.
See, solar panels produce the most electricity during the middle of the day, which also happens to be the time when your home uses the least amount of electricity. A standard grid-tied solar system sends that excess solar energy back to the utility grid.
However, when solar panels are paired with a home battery, excess electricity goes into the battery instead of the grid. Then, when the sun goes down and your panels aren’t producing electricity anymore, you can use the energy you have stored in your battery. instead of paying for electricity from the utility.
This means you get to power your home with all of the clean, renewable solar power your solar panels produce, no matter what time of day it is.
How much do solar batteries cost in 2023?
Depending on the battery’s chemistry, a solar battery can cost anywhere from 200 to over 15,000 to install.
Most residential grid-tied solar panels are paired with lithium-ion batteries, which cost anywhere from 7,000 to 15,000 to install. Some small-capacity lead-acid batteries can cost as little as 200, but they won’t be able to power much in your home and are typically used as emergency backup power for RVs.
The following table lists some of the most popular solar batteries available on the market:
Estimated cost before installation
The cost of solar batteries has decreased over the past few years, but they still cost a pretty penny. and most people don’t have that kind of money just lying around. Luckily, solar batteries are eligible for the 30% federal solar tax credit, and some states even have additional solar battery incentives to help cut down on upfront battery prices.
Find out if battery storage is worth it where you live
Factors that determine solar battery cost
Solar battery manufacturer
Just like everything else you buy, the brand that you choose will impact the pricing of the battery. This is because different brands offer different services and have different manufacturing processes.
For instance, German battery manufacturer sonnen offers a luxury line of solar batteries, some of which cost upwards of 30,000. The Tesla Powerwall on the other hand, costs closer to 13,000, including installation costs!
Battery chemistry
There are many different types of batteries on the market, but most residential systems use lithium-ion batteries.
Two main lithium-ion chemistries are used for solar batteries: nickel manganese cobalt (NMC) and lithium iron phosphate (LFP). NMC batteries, like the LG Chem Prime, have been around a bit longer, making them slightly cheaper than LFP batteries, like the Enphase IQ.
While some homeowners choose to use lead-acid batteries instead of lithium-ion batteries because they are cheaper, they tend to have a shorter lifespan, lower capacity, and require regular maintenance.
Number of batteries installed
This seems like a no-brainer, but the more batteries installed, the higher the solar energy storage system costs. The number of solar batteries you’ll need depends on:
- How many kilowatt-hours of energy you use
- The storage capacity of the battery
- How many appliances you want to power
- How long you want to power your appliances
In most cases, in the event of a power outage, one to two solar batteries will hold enough stored energy to cover your energy needs and provide backup power to a few key circuits.
Backup load panel
In most cases, solar batteries can’t power everything in your home.
The important things will stay on, like your lights and your fridge, but you’ll need to install multiple batteries to have the amount of energy needed to power something like your air conditioner during an outage or if you’re off-grid.
Because a battery can’t power your entire home, you might need to install a sub-panel so that the battery will back up only the most important things in your home during a power outage. Installing a sub-panel, sometimes called a backup load panel or a critical load panel, will add 1,000 to 2,000 to the installation costs.
Labor costs
The amount of labor required to install your battery system will also impact the price of a home solar battery installation.
If the battery is being installed at the same time as the solar panels, the labor costs could be a bit lower because all of the electrical work and permitting associated with both the solar system and battery system will be completed at once.
However, if the battery is being added to the solar panel system after the fact, labor could cost more, as new permits will need to be filed, more incentive forms may be required, and some additional electrical work may need to be done to connect the battery to the existing solar panels.
Incentives and rebates
The cost to install a solar battery can also vary depending on what solar battery incentives are available in your area.
California’s solar battery incentive program, called SGIP, can cover almost a quarter of the costs of a battery installation. Other states, like Oregon, also offer solar battery programs that help lower upfront costs.
Plus, if you qualify for the federal solar tax credit, you can get an additional 30% off the cost of your battery installation, even if the battery isn’t connected to solar panels.
Are solar batteries worth the extra cost?
Although pairing solar panels with energy storage is becoming more common, it doesn’t mean it’s the right choice for everyone.
Installing a solar battery storage solution provides the greatest benefits to homeowners who live in areas that experience frequent power outages, where full-retail net metering isn’t offered, or if there are battery incentives available in their area.
Solar batteries are also great if your main reasons for going solar are environmental, as it maximizes the amount of renewable energy your home uses.
However, if you’re only looking to save extra money, a solar battery might not be worth it for you. What we mean is, if you live in a state with full-retail net metering, you’ll be saving the same amount of money with a battery as you would without one. All the battery would do is add thousands of dollars to your solar installation and provide you peace of mind in the event of a power outage.
Solar panels and solar batteries make a great pair
Installing a solar battery storage system can be a great way to get the most value out of your solar panels.
Batteries are an excellent source of backup power, they increase your energy independence and, in some cases, can even save you more money on your electric bill because you’ll be drawing power from the battery instead of the grid.
However, solar battery systems do come at a price. If you’re looking to save money on your electricity bill, installing a solar battery might not be right for you, especially if your utility offers net metering. However, if you live in an area that experiences widespread blackouts, like the ones in California and Texas, or somewhere with Time-of-Use (TOU) utility rates, having a battery backup to store energy for when you need it will be beneficial.
The upside is that the price of solar battery technology continues to fall, so much so that someday in the near future, solar batteries will come standard with all solar energy systems.
If you’re looking to pair your solar panels with storage, make sure you contact multiple reputable battery storage installers to ensure that you get the highest quality installation at the best possible price.
Rechargeable Solar Battery System For Your Home
Consult with your sales representative for battery availability and backup capabilities in your area. Available while supplies last.
Generate, store, and manage clean, affordable solar energy on your terms. With Sunrun Brightbox, your Brilliant Home™ comes full circle. Brightbox is more than just solar battery storage—it’s a holistic service that puts the power in your hands. We only partner with top-notch innovators in lithium-ion battery technology, so you’re backed by the highest quality products available. Brightbox is currently available to new Sunrun solar customers only.
Sunrun helps you go solar and finds the back-up options that best fit your needs.
Our solar-powered batteries are best-in-class. Choose to back up your whole home with Tesla Powerwall, or just the essentials with LG Chem.
Our customized plans give you the financial flexibility you need. Choose from multiple lease, financing, and cash options.
We’re with you every step of the way. From finding the right solar plan to monitoring your solar system, Sunrun safely sees you through your solar journey with our Solar Guarantee. Go solar virtually with no in-person contact.
Keep the lights on, protect your family and secure your home office during blackouts. Our 100-year-old utility grid is expensive, dirty, and susceptible to extreme weather. As blackouts become the new normal, Brightbox backs you up with reliable, clean energy for your home and family.
Brightbox can buffer you from increasing energy costs so that you have power when you need it most. While we can’t predict how much or how often utility electric rates will rise or when exactly the power will go out, we can always count on the sun rising each day. Take charge of your electric bill and get control of your energy needs now and in the future.
The benefits of solar-powered batteries go beyond your home. Brightbox’s solar battery service enables you to consume more of the clean energy your solar panels produce, so you rely less on dirty and damaging fossil fuels while you decrease your carbon footprint. A cleaner and safer future starts today, and you can help create it by building a smarter energy grid.
Reliable energy when you need it most.
Find solar battery availability, information, and Sunrun locations near you. If we’re not there already, we may be in your community soon. Sunrun is committed to growing solar locally.
What kind of solar batteries does Sunrun use?
Brightbox offers two lithium-ion solar battery storage options: Tesla Powerwall and LG Chem. Compared to lead acid batteries, solar batteries using lithium-ion technology are more efficient and have longer lifespans. This makes them one of the best energy storage options when going solar.
What’s the difference between Tesla Powerwall and LG Chem?
Tesla Powerwall can provide whole home backup while LG Chem backs up to four circuits. There are also differences in the software and app functionality.
Request a free quote to get connected with a Sunrun Solar Advisor and determine which back-up solution will best meet your energy needs.
Are there solar storage incentives available?
One of the best solar storage incentives is the Federal Solar Tax Credit. The Federal Solar Tax Credit will deduct 26% of the cost of your solar energy system from your federal taxes. Starting in 2021, the value of the tax credit will step down to 22%. After 2021, the tax credit for residential solar ends.
Another option is to finance Brightbox with a lease. We’ll pass down the savings to you in the form of a lower and more predictable electric bill.
Net metering, which credits any excess power your solar system generates back to your electric bill, is another great incentive for many people that go solar. However, several states have chosen to adopt Time-of-Use (TOU) rates, which complicate the way your net metering credits are calculated. Brightbox can buffer you from peak TOU rates so you may save even more on your electric bill.
Will my Brightbox battery allow me to go off grid?
Our rechargeable solar battery systems are designed to keep you on-grid during normal service times while still providing reliable backup when the sun isn’t shining or during the event of an outage. This is the most reliable and economical way to use your Brightbox system, and the one most strongly recommended by Sunrun’s service experts.
How much storage does my home need?
Just like solar-only systems, the size of your rechargeable solar battery system is determined by your unique energy needs and habits. Factors, such as the amount of electricity you use at home and the devices and appliances you want to back up, will play a key role as you select the right battery storage solution for you.
Do I need solar panels to use Brightbox?
Aside from very rare exceptions, Sunrun’s Brightbox service includes rooftop solar panels.
Where will my Brightbox battery be placed?
The installation of Brightbox is a relatively simple process. It’s about the size of a water heater, and the system is mounted on a wall—usually inside your garage or outside of your home.
Is my Brightbox battery an IoT (internet of things) device?
While Brightbox requires an Internet or cellular connection to monitor your energy storage and usage efficiently, it can still operate without it. If for some reason Brightbox happens to go offline, you can resume your usage tracking when your internet connection is back to normal.
Do I need to do any setup or maintenance to Brightbox?
Most residential batteries are installed and configured with baseline settings by your solar installer. Solar batteries last anywhere between 10 and 15 years, and manufacturers typically offer a 10-year warranty.
How does Brightbox work?
Brightbox allows you to store the electricity your solar energy system produces during the day and use it when you need it most—such as in the evening during time of use (TOU) peak pricing or when the electric grid fails due to an extreme weather event or physical damage to the equipment.
What is Brightbox?
Brightbox is a holistic solar battery storage service that offers you clean, safe, reliable, back-up power to have better control over your home energy use and cost.
What are the benefits of Brightbox?
Brightbox solar battery storage systems can help you save money on utility bills, protect your home from power outages, and reduce your carbon footprint by supporting the production of clean, renewable energy.
Solar Battery Buying Guide: Everything You Need to Know
Want to go off the grid or earn energy bill credits? Adding a battery to a solar panel system may be the answer. Here’s what you need to know.
Taylor Freitas is a freelance writer and has contributed to publications including LA Weekly, Safety.com, and Hospitality Technology. She holds a B.A. in Print and Digital Journalism from the University of Southern California.
Laura Leavitt is a personal finance and wellness writer for CNET. Her work has been published at NextAdvisor, Bankrate, The Simple Dollar, MoneyGeek, Business Insider and more.
Full energy independence isn’t achievable without solar batteries.
Solar panels can generate electricity only when the sun is shining. But with solar batteries, you can store that energy for use at night, during an outage or to sell it back to your utility or apply as bill credits.
Backup solar batteries run on electricity and can either work as a standalone device or as part of a home solar system. When the lights go out, your backup battery system will automatically switch on and serve as source of electricity for several hours, a day or longer.
If people have solar as well as a battery, they can use the solar in the day to feed their houses and charge their batteries. And at night, the batteries will serve their houses instead of the grid, Kim Quirk, a branch manager at ReVision Energy, told CNET recently. It makes people a bit more independent from the grid when we tend to see big spikes.
However, all of these benefits come at a cost. Installing a battery backup system can be a significant investment, so it’s important to understand what’s involved. For this guide, we’ve answered some of the most common questions about battery backup systems, including how they work, how they’re made, how much they cost and where you can buy them.
How solar batteries work
When your home doesn’t need all the energy being produced by your solar panels, the excess energy is stored in the battery. When the solar panels aren’t generating enough energy to fill the power needs of the building, the battery discharges reserve power to make up the difference.
The way you configure your solar battery system affects how it works. You have three main options:
- Connect to your solar panels: Batteries connected to solar panels will fill and discharge frequently in response to the times without sun that you still want electricity. This is useful when in an area that is off-grid, away from electrical utilities.
- Connect your solar panels to a solar battery system andto the grid: You can choose to fill your battery and just keep it as a backup, rarely discharging it, and mostly selling and buying excess electricity from the electric company.
- Use battery duringtime of use ratespikes: If you live in an area where electricity rates vary with the time of day, you can configure your system to use battery backup at the most expensive times and to buy electricity from the grid at the least expensive times.
Benefits and drawbacks of battery backup systems
Whether you have solar panels or not, battery backups offer plenty of benefits. For starters, they help you gain energy independence, so you don’t have to rely on the public power grid. This is especially critical if you live somewhere with frequent outages or blackouts.
On top of that, battery backups don’t operate on fossil fuels and provide your home with clean energy. Unlike generators, they’re nearly silent to run and don’t emit carbon into the atmosphere.
Even if the power hasn’t gone out, you can use your battery backup as a way to save money on your electric bills. For example, if you’re on a time-of-use utility plan, you can draw on the energy from your battery during peak hours rather than paying sky-high electricity rates to your energy company.
Pros of solar batteries
- Energy independence
- Save money on energy bills
- Less or no reliance on utility
- Power your home during an outage
- Clean energy
Cons of solar batteries
- Expensive, sometimes as much as a solar system
- High upfront costs
- Limited capacity
Different types of solar batteries
There are several kinds of batteries used in battery backup systems, including lithium-ion, lead-acid and flow batteries. Here’s a quick overview of each type.
Lithium-ion batteries
Lithium-ion batteries are the most common for home systems. Most of today’s popular battery backup products are lithium-ion, including the Tesla Powerwall, Panasonic EverVolt and Generac PWRcell. They’re lightweight and energy-efficient, making them perfect for home use.
Lead-acid batteries
Lead-acid batteries have been used for hundreds of years and are the primary type of battery used in cars. They’re cheaper than lithium-ion, but they aren’t as efficient, which means they’re best suited for small systems.
Flow batteries
Flow batteries (or redox flow batteries) are less common in home systems since they’re mainly designed for commercial use. However, the technology appears promising, and it could become more widely used in residential battery backup systems in the near future.
Nickel-cadmium batteries
Nickel-cadmium batteries have a high energy density with double the energy of a lead-acid battery. Nickel-cadmium batteries are very durable, expensive and work well in extreme temperatures making them a good choice for large-scale commercial and industrial projects. Cadmium is toxic, however, and generally not appropriate for residential use.
Buying a backup battery system
You can get battery backups from a range of businesses, including manufacturers, solar companies and battery retailers. CNET curated a list of the best batteries here. The price will depend on which battery model you choose and how many you buy for your system. According to the US Department of Energy, solar batteries can cost anywhere from 12,000 to 22,000.
If you’re buying a battery backup as part of a solar panel system, however, you may qualify for a rebate or tax credit.
How to set up a battery backup system
Once you’ve decided on a battery or batteries, make sure to have it professionally installed.- otherwise, you run the risk of injuring yourself. You can expect to pay a few thousand dollars for installation (which is separate from the cost of the battery).
Maintaining a battery backup system
After the initial setup, there’s little maintenance required on a battery backup system. You won’t need to replenish a fuel source (like you would with a generator), and there’s no need for regular maintenance.
Lifespan and warranties
A few years after installation, you may notice that your battery backup system doesn’t hold a charge as well as it used to. That’s because, like other types of batteries, battery backups lose storage capacity over time.
To account for this, battery backups include a warranty that expresses how efficient the battery should be by the end of the warranty period. Many of the top solar batteries offer 10 years and 70%, meaning that by the end of the 10-year warranty, the battery should still operate at 70% of its original performance.
Inverters and batteries
Inverters play an important role in how the battery stores and converts solar energy. While solar panels generate electricity in direct current, or DC, the electric grid and homes generally use alternating current, or AC. An inverter can convert AC to DC or vice versa, and most solar batteries include an inverter to store the energy in DC form, as well as an inverter to convert it back into AC to be used in the grid or the home.
Because inversion of current isn’t perfectly efficient, battery producers are always experimenting with how to invert less often and increase the efficiency of the battery. As a result, some batteries will not have inverters for both input and output included in the system. Talk to your solar installer about the battery system you’re considering so that you can make sure you have all the external inverters you need.