What is the best solar battery for your home?
Each year, it’s becoming more common to install solar batteries with solar panels. They provide significant benefits, such as energy independence and emergency backup power, but it can be difficult to know exactly what to look for when shopping for a solar battery.
In this blog, we break down everything you need to know about solar batteries to pick the right one for your home.
On this page:
- What is a solar battery?
- What are the benefits?
- Features to look for
- Types of solar batteries
- Solar battery cost
- Solar batteries with panels
What is a solar battery?
Solar batteries are used to store energy that solar panels produce. The stored solar energy can then be used later on, when it is needed.
Solar panels make more electricity during the middle of the day than they do at any other time of day. The middle of the day also happens to be when your home uses the least amount of energy. Because of this, your solar panels will produce a lot of electricity that your home won’t need at that time.
Solar batteries are able to store that extra energy from the middle of the day so you can use it at a different time.
There are many solar batteries on the market that can store your excess solar energy. Image source: SolarPowerRocks
What are the benefits of solar battery storage?
A solar battery could be a great investment for your home, depending on what you want to get out of your battery storage system. There are a few reasons why you might want to install a solar battery.
Less dependence on the grid
For one, solar batteries allow you to be less dependent on the grid. Having great energy independence also means that you have the ability to power your home entirely with clean solar energy.
Producing clean energy
Utilities derive the majority of their electricity from dirty fossil fuels. Installing a solar battery ensures that you will power your home entirely with renewable energy produced right on your roof!
Access to backup power
The utility grid can be unreliable. Solar batteries can be used as a backup power source when the grid goes down. It is especially useful to have a backup battery bank in places like California, where grid outages are common during wildfire season.
Big savings on your electric bill
Solar batteries also have the potential to save you money on your electric bill. This is especially true if your utility uses a time-of-use rate structure. This means that your utility will charge different rates for electricity depending on what time of day it is. Solar batteries can also offer bill savings if your utility does not offer full retail net metering.
What features to look for when shopping for solar battery storage
There are 4 key features to consider when looking to buy a solar battery: the power and capacity ratings, the depth of discharge, the efficiency rating, and the warranty.
Let’s take a closer look at each of these terms and what they mean.
1. Power and capacity ratings
The first thing you need to look at when purchasing solar battery storage is its capacity rating and the power rating. The capacity rating tells you how many kilowatt-hours (kWh) of electricity a solar battery can hold.
You can install multiple batteries to increase the capacity of your solar storage system. It represents the actual supply of (or how much) electricity you have stored in your battery.
The capacity rating isn’t very useful on its own. You also have to consider the power rating of a battery. The power rating tells you how much electricity a battery can deliver to your home at one time, measured in kilowatts. This will give you an idea of how many appliances you can power in your home with a solar battery.
If a battery has a high capacity, but a low power rating, it will be able to power a few important appliances, like a refrigerator and an electric water heater, for a prolonged period of time. These types of batteries are useful if you are looking to use your battery as an emergency backup generator.
A battery with a low capacity and a high power rating will be able to power the whole house, but only for a few hours because there are fewer kWhs stored in the battery.
2. Depth of discharge (DoD)
The depth of discharge (DoD) of a solar battery is the percentage that a battery has been discharged relative to the total capacity of the battery. Most solar batteries will have a specific DoD listed to maintain the health of the battery.
For example, let’s say you have a solar battery with a 10 kWh capacity with a recommendedDoD of 60%, you shouldn’t use more than 6 kWh of electricity before you recharge it. Using any more than 6 kWh could damage the battery.
Higher DoD ratings allow you to use more of the energy stored in your solar battery before you have to recharge it.
3. Round-trip efficiency
The round trip efficiency of a solar battery represents the amount of energy you can use from your solar battery compared to the amount of energy it took to store that energy.
So, let’s say your solar panels had 10 kWh of electricity to send into your battery, but you only have 8 kWh of electricity that can be used. This makes the battery’s round-trip efficiency 80%. The other 2 kWh were used by the battery system to actually store and release the electricity.
High efficiency batteries will end up saving you more money, because more of the electricity that you produce will be usable than if you had a lower efficiency battery.
A solar battery’s warranty will give you an idea of how long the battery should last. As you use your solar battery, it will do something called “cycling”. A cycle is when your battery charges and then drains to the recommended DoD. Each time a battery cycles, the battery’s ability to hold a charge, or its capacity, decreases.
How you use your solar battery influences how many cycles it will go through. Because of this, solar battery warranties guarantee that a battery will operate at a certain capacity for both a specified number of years and a specified number of cycles, or cycle life.
For example, let’s take a look at the sonnen EcoLinx solar battery warranty. Sonnen’s warranty guarantees that their EcoLinx LFP2 model will operate at 70% of its original storage capacity after 10 years or 10,000 cycles, whichever comes first. If you use the battery to power your home daily, it is likely that you will reach 10,000 cycles first. If you only use the battery as emergency back up solar solar power, you might reach 10 years before you hit 10,000 cycles.
Most residential solar batteries are believed to last for at least 10 years with regular use.
But again, it is important to keep in mind that the lifespan of a solar battery depends on how it is used. You will get more out of your battery if the warranty has a long cycle life.
Are there different types of solar batteries?
Yes, there are many different types of solar batteries on the market, including lead acid batteries, lithium ion batteries, flow batteries, and salt water batteries. However, most residential energy storage systems are composed of either lead-acid or lithium ion batteries.
We’re going to take a closer look at these two popular home solar storage options.
Lead acid solar batteries
Lead acid batteries have been used for energy storage for decades. There are two types of lead acid batteries:
- Flooded lead acid batteries: Require maintenance every one to three months to ensure they operate properly
- Sealed lead acid batteries: Maintenance-free, a better energy storage option if you don't want to deal with regular upkeep
What are some of the features of a lead acid battery?
Lead acid batteries tend to be the cheapest solar battery option, however they are much larger and heavier than other batteries. This means they require more space per kWh of storage than other types of batteries.
They also have a lower DoD, usually around 50%. So they need to be recharged more frequently to operate properly. Most lead acid batteries have a lifespan of anywhere from 5 to 10 years. Lead acid batteries tend to be the most popular option for off-grid solar storage systems.
Lithium-ion solar batteries
Lithium-ion batteries are a new kind of energy storage technology. However, they have quickly become a favorite among homeowners for a few reasons. One being that they are smaller and lighter than lead-acid batteries, so they take up much less space for the same amount of capacity. They also tend to have a longer lifespan, usually with a minimum of 10 years.
Lithium-ion batteries’ longer lifespan is partially due to the fact that they have a higher DoD. This means that you can deplete the battery further than a lead acid battery before you need to recharge. Many popular lithium-ion solar batteries have DoD’s of 90% or higher.
One downside to lithium-ion solar batteries is that they could catch fire if they are not used properly or if they are overcharged; this is called “thermal runaway”. However, thermal runaway is extremely uncommon, especially because lithium ion solar batteries have advanced software to prevent this from occurring. If your battery is installed properly, the chances of it catching on fire is almost zero.
How much do solar batteries cost in 2020?
The cost of solar batteries varies depending on the battery’s chemistry. Lead acid batteries tend to be the cheapest solar battery option, making them the best storage solution if you have a tight budget. However, lead acid batteries have short lifespans, low DoDs, and require a lot of space.
Lithium-ion batteries beat lead-acid in all of those categories. But, lithium-ion batteries come at a higher price. The good news is that the price for lithium ion solar batteries has continued to fall over the years. They have quickly become the most popular energy storage options for grid-tied solar systems.
The following table lists some popular solar batteries on the market:
|LG Chem RESU||$8,750||Lithium-ion||9.3 kWh||10-year|
|Tesla Powerwall 2||$6,500||Lithium-ion||13.5 kWh||10-year|
|Sonnen Ecolinx||$33,000||Lithium-ion||12 kWh||15-year|
|Universal UB121000-4597 8 12v 100AH Deep Cycle AGM Battery||$179.99||Lead Acid||1.2 kWh||1-year|
|Trojan (SPRE 06 255)||$201.26||Lead Acid||1.4 kWh||5-year|
Solar panels and solar batteries make a great pair
Installing a solar battery can be a great way to get the most value out of your solar panel system. They are an excellent source of backup power, can make you less reliant on the grid, and in some cases can save you even more money on your electric bill.
However, solar battery systems do come at a price. If you’re looking to save money, 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 regular blackouts or somewhere with time-of-use utility rates, having a battery backup could be beneficial.
The upside is the price of solar batteries continues to fall, so it is possible that all solar systems in the future will be installed with them. It’s important to understand all of the benefits and features of solar batteries, so you can make an informed decision about what is right for your home.
- Solar batteries can be used to store extra energy your solar panels produce during the day for use later.
- The main benefits of solar batteries include energy independence, emergency backup power, and in some cases - energy bill savings.
- When shopping for solar batteries you should consider the following: the power and capacity ratings, the depth of discharge, the round trip efficiency, and the warranty.
- There are two main battery types for residential solar systems - lead acid batteries and lithium ion batteries.
- The cost of solar batteries varies depending on its chemistry.
Author: Catherine Lane | SolarReviews Blog Author
Catherine is a researcher and content specialist at SolarReviews. She has strong interests in issues related to climate and sustainability which led her to pursue a degree in environmental science at Ramapo College of New Jersey.