Backup Battery Buying Guide

Interest in solar energy storage has grown significantly over the last couple of decades. According to the Solar Energy Industries Association (SEIA), most homeowners and businesses are increasingly opting for solar systems paired with battery storage.

And while this trend is quite new, its growth over the next couple of years is expected to be immense. In the next 5 years, it’s expected that over 25% of all power solar systems will have some form of energy storage.

If you are planning to install a solar system paired with battery backup, you may be wondering where to start. Well, you’ve come to the right place. In this battery backup guide, we will provide you with all the information that you need about storage batteries for solar panels. And by the end of this guide, you will have all the information that you need to help you make an informed decision.

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Why Adopt A Battery Backup System

So, why should you install a battery backup system for your home or business? Battery backup systems offer a wide range of benefits. For instance, when you pair your solar energy system with a battery backup system, you can store the extra energy produced, instead of offloading it back to the electricity grid. In short, you will be fully maximizing your solar energy system every day. And when you need more power than your solar panels can produce, you will use the energy that you stored when they were operating at maximum capacity.

Furthermore, some electricity utility companies are increasingly changing their rates, making battery backups a cost-effective investment for homeowners and businesses. If your power utility company uses any of the following rate policies, then you will realize cost-savings when you install a battery backup system for your solar power:

  • Time of Use Rates (TOU): If your power utility company uses TOU rates, then it means that the cost per kWh, will depend on the time of the day. But generally, electricity costs more when demand is high – especially in the late afternoons and evenings. On the other hand, the cost per kWh will be lower during the off-peak hours. And this is during the daytime when solar panels are most productive and reliance on the grid is low. So, if your local utility company uses TOU rates, then you will realize some energy savings by using the energy stored in your battery backup during peak hours.


  • Demand charges: If your power utility company applies demand charges, they will charge you a fee based on your consumption. In most cases, the fee will depend on the amount of power that you draw from the grid during peak hours. Also, the fee may be determined by the amount of power that you consume in a month. So, if your utility company uses this method, installing a battery backup system can save you some money, since you will avoid the high fees charged for using electricity during peak hours. Instead of using electricity and incurring high fees, you will rely on the power stored in your battery backup. As much as this method is mostly applied to commercial power consumers, some utilities in states like Illinois and Arizona are planning to introduce demand charges to residential customers, in an attempt to discourage over-reliance on the grid.


  • Reduced or no net metering credits: If your state applies a true net metering system, then you will receive some power credits based on the amount of power that your solar panels produce. For instance, if you pay $0.65 per kWh of electricity, then you will receive a $0.65 credit on your electricity bill per month, for every kWh that your solar panels produce and offload to the grid. In such states, installing solar energy storage systems will be a worthwhile investment.

While a battery backup system may cost more to purchase and install than a traditional diesel generator, they will provide you with clean backup power, without polluting the environment. Also, it’s important to note that if you have a conventional solar panel system without a storage system, you may not enjoy all the benefits that come with installing solar power. For instance, if there is a power outage, your home can still run optimally using the power stored in the solar energy batteries. As you can see, installing a solar energy system paired with some form of energy storage makes a lot of financial sense.

Battery Backup System Types

There are 4 main types of solar power storage batteries. These are lead-acid, lithium-ion (iron phosphate), lithium-ion (nickel-based) and flow batteries. Each type of battery has its strengths and drawbacks.

  • Lead-acid batteries: These batteries have been around for many decades. They are arguably the most popular storage option for most people. As much as they have a shorter lifespan compared to the other batteries, they are currently the most affordable especially for home power storage. So, if you are a homeowner looking for battery backup system, then you should check out lead-acid batteries.
  • Lithium-ion batteries: Lithium-ion batteries are relatively new on the market. They are more compact and lighter, compared to lead-acid batteries. Also, they come with a higher depth of discharge (DOD) than lead-acid batteries. Furthermore, lithium-ion batteries require minimal regular maintenance. But as you may expect, lithium-ion batteries are costlier than lead-acid batteries. Tesla Powerwall and LG Chem Resu are two of the most popular lithium-ion battery backups. Lithium-ion batteries are best suited for residential solar power installations, thanks to their compact design. Also, they will allow you to draw more of the power stored in the battery.
  • Nickel-cadmium batteries: As much as these batteries have been around for many decades, they are not as widely used in homes as lithium-ion batteries and lead-acid batteries. Their main benefit is their durability. Also, they can comfortably operate at extremely high temperatures. Just like lithium-ion batteries, nickel-based batteries don’t require intense regular maintenance. Their main drawback is that cadmium is highly toxic. And for this reason, some people are now replacing nickel-cadmium batteries with nickel manganese batteries.
  • Flow batteries: As their name suggests, flow batteries use a liquid-based electrolyte to store power, instead of solid electrodes like those found in lithium-ion batteries. One of their main strengths is that they have a 100% DOD, meaning, you can use all the power stored in the battery without damaging its health. Also, the liquid electrolyte used in these batteries is a fire-retardant, meaning you don’t have to worry about them catching fire. They have the longest lifespan, compared to the other options, which is approximately 30 years. Also, they are low-maintenance batteries. On the other hand, they are expensive to install. Also, they require a substantial amount of space, owing to their big size. Therefore, they are best suited to large utility applications, commercial settings, as well as off-grid projects where space is not an issue.

So, which battery should you choose among the 4 options? The best battery backup system for alternative energy will depend on your needs, available space, and budget. For example, lithium-ion batteries will hold more energy and will only require a small amount of space. Furthermore, they are highly efficient, compared to lead-acid batteries. However, if you are on a budget, then lead-acid batteries may be the best option for home use.

Determining Your Solar Storage Options

It’s extremely important to first determine your solar storage needs, before buying a solar battery. Unfortunately, most people tend to overlook this step. And in the end, they usually end up underestimating or overestimating their storage needs. Fortunately, you can easily determine your storage options using the sizing calculators that most solar battery manufacturers provide. You can use that information to determine the battery capacity that you need for your premises.

Factors to Consider When Buying Battery Backup Systems

When it comes to buying a battery backup system, you don’t just choose any that you come across. You need to pay attention to various specifications and factors, to ensure you choose the right solar energy storage for your home or business. Having said that, here are some of the factors that you need to consider when buying a battery backup system:

  • Capacity: A battery’s storage capacity refers to the amount of power that it can hold. Different batteries have different capacities. So, when buying a battery backup system, you need to ensure you choose a battery whose storage capacity can comfortably accommodate your needs.
  • Price: When buying a battery backup, some customers will go for the cheapest they can find. Unfortunately, most of the cheaper battery backup systems on the market don’t last long. On the other hand, you don’t have to spend an arm and a leg on a battery backup system. When it comes to price, it’s advisable to buy the best battery backup system that you can afford.
  • Cycle life: Cycle life refers to the number of times that a battery backup can charge and discharge before its capacity drops to below optimum levels. For instance, a battery backup system may be warrantied at 6,000 cycles or 15 years at 80% capacity. So, by the end of the warranty period, the battery shouldn’t have lost more than 20% of its original storage capacity. The more the number of cycles, the higher the price.

Which Solar Storage System Should You Choose

Whether you are installing a new solar energy power system or you are planning to add a battery backup to your existing solar system, there are plenty of systems to choose from. They include DC-coupled energy systems, AC coupled energy systems, and bi-directional AC-coupled energy systems with islanding. Each system has its pros and cons. So, make sure you consult a qualified and experienced solar power installation technician before you choose a system for your home or business.

Commercial Storage Battery Systems for Businesses

Battery backup storage solutions are not designed for homeowners only. Therefore, businesses of all sizes stand to benefit by installing battery backups for their solar systems. When you install a storage system for your solar power system, your business stands to benefit in the following ways:

  • Demand reduction: Installing a battery backup system for your business will reduce your reliance on electricity. And this can significantly boost your bottom line.
  • Enhanced solar power system: Some companies don’t have enough roof space to install a reliable solar power system, which may help to reduce their reliance on electricity. But when you combine a solar power system with a storage method, you will only need a few solar panels to produce adequate energy for your needs.
  • Move away from back-up generators: Most businesses use diesel-powered and petrol-powered generators as their main method of power backup. The problem is, these generators emit harmful gases to the environment. Furthermore, you also need to buy petrol or diesel to keep them running. But when you shift to solar panels with a storage system, you will have a clean energy backup system. Also, you no longer have to spend money on diesel or petrol.

Battery Storage Glossary

When shopping for a storage solution for your solar power system, you may come across lots of confusing terms and specifications. Some of the terms that you may come across include:

  • Capacity and power: As noted earlier, capacity refers to the total amount of power that a battery backup can hold. Capacity is usually measured in kilowatt-hours or kWh. It’s also important to check the battery’s power rating, which is the amount of power it can deliver at one time.
  • Depth of discharge (DOD): This refers to the amount of power a battery needs to retain when discharged. Manufacturers usually specify the maximum battery DOD to ensure optimal performance. For example, if a 20kWh battery has a DOD of 80%, then you shouldn’t use more than 18kWh of its power before you recharge it.
  • Round-trip efficiency: Round-trip efficiency is the percentage of power stored in a battery backup that you can retrieve. For instance, if you store 10kWh of electricity into your battery backup and you can only retrieve 8kWh per hour from it, then it has a round-trip efficiency of 80%. A battery backup system with a high round-trip efficiency will offer more value for money.

Battery Backup Storage FAQs


  1. How long does battery backup last?
    A solar battery’s lifespan will depend on its type and make. But on average, you should expect a useful lifespan of 5 to 15 years.
  2. Can I extend the lifespan of my backup battery?
    Proper maintenance and storing your battery within optimal temperature ranges can considerably extend the life of your solar batteries.
  3. How long can battery backup power my home?
    The actual duration will depend on various factors, including your home’s energy load, your batteries’ power rating and capacity as well as whether you are connected to the grid.