The length of time the solar battery will last or the amount of power it can provide are some of the specifications you should consider when evaluating your solar battery options. Listed below are the different types of solar batteries, along with all of the criteria you should consider when comparing home energy storage options.
How to compare your solar storage options?
If you’re considering solar-plus-storage options, you’re going to come across a lot of complicated product specifications. In your evaluation, you should take into account the battery’s capacity and power ratings, depth of discharge (DoD), round-trip efficiency, warranty, and manufacturer.
Capacity & power
Solar battery capacity is the total amount of electricity it can store, measured in kilowatt-hours (kWh). Most solar batteries are stackable, which means you can add multiple batteries to your solar-plus-storage system.
Battery capacity tells you how big your battery is, but it does not tell you how much electricity it can provide at any given time. The battery’s power rating is also important to consider for a complete picture. In the context of solar batteries, a power rating determines how much power a battery can deliver at a given time. It is measured in kilowatts (kW).
The battery with a high capacity and a low power rating would deliver a low amount of electricity (enough to run a few appliances) for a long time. The battery with a low capacity and a high power rating would run your whole house, but only for a few hours.
Depth of discharge (DoD)
Due to their chemical composition, solar batteries need to retain some charge at all times. If you use 100 percent of a battery’s charge, its useful life will be significantly reduced.
A battery’s depth of discharge (DoD) indicates the percentage of its capacity that has been used. Manufacturers usually specify a maximum DoD for optimal performance. For example, if a 10 kWh battery has a DoD of 90 percent, you shouldn’t use more than 9 kWh of the battery before recharging it. Generally speaking, a higher DoD will allow you to utilize more of your battery’s capacity.
The round-trip efficiency of a battery shows how much energy it can use as a percent of the energy it took to store it. When you feed your battery five kWh of electricity and only get four kWh of useful energy back, the battery has an 80 percent round-trip efficiency (4 kWh / 5 kWh = 80%). A battery with a higher round-trip efficiency will generally provide you with more economic value.
Battery life & warranty
Using home energy storage typically requires the battery to go through a daily charge and discharge cycle. Just like your cell phone battery, as you use it more often, its ability to hold power is diminished. Most solar batteries have a warranty of either 5,000 cycles or 10 years at 70 percent capacity, meaning that after the warranty has expired you should expect no more than a 30 percent decrease in energy retention capability.
As part of your solar battery warranty, you will receive a certain number of cycles and/or years of useful life. During the warranty period, most manufacturers will also guarantee that the battery will retain a certain amount of its capacity despite natural degradation over time. Therefore, the simple answer to the question “how long will my solar battery last?” is that it depends on the brand of battery you buy and how much capacity it will lose over time.
Solar battery products are being developed and manufactured by a variety of organizations, including automotive firms and startups. Despite having a longer history of product manufacturing, a major automotive company entering the energy storage market may not offer the most revolutionary technology. A tech startup on the other hand may have a brand-new high-performance battery, but not a long-term track record.
It is important to evaluate the warranties associated with each product before choosing a battery manufactured by a cutting-edge startup or one with a long history.
Energy storage is becoming a hot topic among automotive companies
Both home energy storage technology and electric vehicles use advanced batteries to create more efficient, sustainable products that reduce greenhouse gas emissions.
As electric vehicles become more popular, companies are dedicating significant research and development funds to developing batteries, and they’re expanding into energy storage. In 2017, Mercedes-Benz and BMW will also introduce standalone batteries to the market (with their Powerwall batteries). Tesla is the first mainstream example (with its Powerwall battery).
How long do solar batteries last?
The first way to answer this question is to determine how long a solar battery will last. When your solar panels aren’t producing energy, a fully charged battery can often run your home overnight. The amount of energy consumed by your household in a given day, the capacity and power rating of your solar battery and whether you’re connected to the electric grid will all be important to know in order to make an accurate calculation.
To make an accurate calculation of the size of a battery needed to implement a solar plus storage solution, we’ll consider average electricity consumption data from the U.S. Energy Information Administration. A typical home uses 30 kWh of energy per day and a solar battery can usually offer 10 kWh of capacity. Therefore, with three batteries, you could power your residence for 24 hours without an additional source.
As a matter of fact, the answer is more complex. Your solar panel system will also produce power during the day, which will supply strong power for about 6-7 hours during peak sunlight hours. As a result, your 10 kWh battery likely has a useful capacity of 9 kWh as it cannot run at maximum capacity and generally peaks at 90% DoD (as explained above).
Ultimately, if you have a solar PV array, one or two batteries may be enough to supply you with power during the night. Conversely, if you are looking to disconnect from the grid, you should factor in several days’ worth of backup energy storage as cloudy weather can affect your system. In that case, 3 or more batteries might be needed to satisfy your home’s electricity needs for a full 24 hours.
Solar battery lifespan
A solar battery typically lasts between five and fifteen years. If you install a solar battery today, it will probably need to be replaced at least once to match your PV system’s 25-30 year life expectancy. As the market for energy storage solutions grows, solar batteries are expected to follow suit, just as the lifespan of solar panels has increased significantly in the past decade.
Proper maintenance is key to maximizing your solar battery’s lifespan. Temperature can have a significant effect, meaning it’s important to protect it from extremes. Below 30° F, more voltage is required for full charge, and above 90° F the battery may overheat necessitating a reduction in charge. To counteract this, many leading manufacturers such as Tesla offer temperature moderation features but if your battery does not have this you should look into options like earth-sheltered enclosures. Quality care for your solar battery can pay dividends in terms of longevity.
What are the best batteries for solar?
In most cases, lithium ion batteries are the best choice for solar panel systems, but other battery types may be more inexpensive. Home energy storage batteries are typically made of one of three chemical compositions: lead acid, lithium ion, and saltwater.
Off-grid energy systems have relied on lead acid batteries for decades as a tested technology. They are also one of the least expensive options currently available on the market in the home energy storage sector, despite having a relatively short life and lower DoD. If you want to go off the grid and need to store a lot of energy, lead acid batteries are an excellent choice.
A lithium ion chemical composition is used in most new home energy storage technologies. As compared to lead acid batteries, lithium ion batteries are lighter and more compact. They also have a higher DoD and a longer lifespan. However, they are more expensive than lead acid batteries.