The Best Solar Batteries to Store Solar Energy
What is a Solar Battery?
A solar battery, also sometimes referred to as a ‘home battery’, is a device which stores electricity for later use. Usually this is electricity generated from the sun, making it a perfect addition to your solar panels. However, solar batteries can also store electricity from the grid if need be.
You can use this stored energy to power your home when your solar panels don’t generate enough electricity, such as at night or during extreme weather conditions. Some solar battery storage systems even work during power outages, so you can continue to use your home appliances without any disruptions. Meaning you could potentially be 100% independent from the grid.
Furthermore, for those of you who want to make some extra money, in the UK it’s possible to sell your solar battery’s stored surplus energy back to the grid through the Smart Export Guarantee (SEG). Alongside free solar energy generated from your solar panels, solar batteries can also help you save money through the grid by charging your battery during cheaper off-peak hours.
According to Powervault, you can reduce your energy bills by up to 50% through storing your solar energy during the day and then using it in the evening. And you can potentially reduce them by a further 15% if you only purchase electricity from the grid through cheaper night tariffs like Economy 7.
If you’re already interested in these benefits of owning a solar battery and are curious about how you can get one, then we recommend you maximise your savings further by comparing installers to get the best deal. You can compare up to 4 solar batteries free of charge and with no obligation by simply selecting your region below.
How do Solar Batteries Work?
In this section we’ll talk you through the science behind lithium-ion solar batteries and also how your solar battery works as part of your solar panel system.
Lithium-Ion Solar Batteries
Lithium-ion batteries are currently the most popular type of solar battery on the UK market. Brands such as Tesla and LG Chem use this form as their choice of solar battery. It’s also the same technology that’s being used in your smartphone.
Lithium-ion batteries go through a process where they convert stored chemical energy into electrical energy. This process happens when lithium ions release free electrons, which flow from a negatively-charged electrode (anode) to a positively-charged one (cathode).
This movement is encouraged by lithium-salt electrolyte, a liquid inside the battery that provides positive ions. This flow of free electrons creates the electrical current which people can use for the appliances in their homes.
When you use electricity from the battery, the lithium ions flow back to the positively-charged electrode. Simultaneously, electrons move from the negatively-charged electrode to the positively-charged one via an outer circuit, powering the device.
Solar batteries are a combination of multiple ion battery cells and modern electronics that are able to regulate the safety and performance of the whole solar battery storage system. This means that solar batteries can function as rechargeable batteries by using the power of the sun to initiate this whole process and create an electrical current.
How Solar Batteries Work with a Solar Panel System
First of all, how your solar battery works depends on how your solar panels are wired to your solar battery storage system. This could be either direct current (DC) coupling or alternating current (AC) coupling.
Before we get into the step-by-steps, it’s important to highlight that solar cells create DC electricity while the appliances in your home use AC electricity. Furthermore, solar batteries can only store DC electricity. This means that the electricity will need to be converted, but at which points it's converted depends on whether your battery has DC or AC coupling.
DC-coupled solar system:
- During the day, solar panels convert sunlight into DC electricity.
- The electricity is then stored in the battery as DC electricity.
- When required, the DC electricity leaves the solar battery and enters an inverter which converts it into AC electricity that can be used by appliances in the home.
AC-coupled solar system:
- During the day, solar panels convert sunlight into DC electricity.
- The electricity then enters the inverter and is converted into AC electricity to be used in the home.
- Surplus energy then flows through another inverter to convert back into DC electricity which can be stored in the battery.
- If the energy stored in the battery needs to be used in the home at a later point, such as at night, then it must convert back to AC electricity again through the inverter.
In addition to these steps, it is also possible to convert AC electricity from the grid into DC electricity to be stored in your battery. It’s advisable to do this at night when electricity from the National Grid is typically cheaper. Depending on your energy supplier, it’s also possible to do the reverse of this by converting your stored DC electricity into AC electricity to be sold back to the grid.
There is also the option of having a hybrid inverter, which is a single device that can both convert DC electricity into AC electricity and vice versa. Hybrid inverters are growing in popularity as it means you only need one inverter for your home.
When choosing between an AC-coupled or a DC-coupled battery storage system for your home, there’s two important things to consider. The DC-coupled system is typically more efficient due to the fact the energy goes through an inverter less often. However, DC-coupled systems are also more complex to install, making the initial costs of an AC-coupled system usually cheaper.
Solar Batteries: Prices
Currently, solar batteries roughly cost between £1,200 and £14,800. These prices vary widely due to factors such as differences in capacity and battery type. This also means that you’re likely to find a solar battery that fits your home’s energy needs.
Even though there have been some fluctuations in cost, the overall trend of solar battery prices is decreasing. This is a similar situation to when photovoltaic systems were new. As technology improves and solar batteries increase in popularity, the costs will naturally decline. Therefore, these current prices are predicted to decrease further.
Below is a table of some of the most popular batteries on the market and an estimation of what they cost in 2022:
|Solar Battery||Usable Capacity (kWh)||Approx. Cost (excl. Installation)|
|Tesla Powerwall 2||13.5||£9,390|
|Powervault 3||4.1 – 20.5||£4,700 – £14,800|
|LG Chem Resu 10H||9.3||£5,100|
|Enphase Encharge 10T||10.08||£7,990|
|Duracell Energy Bank||3.3||£4,499|
|Varta Pulse 3 and 6||3.3 – 6.5||£3,950 – £5,350|
Even though the initial price of solar batteries can be expensive, a plus is that they require little to no maintenance, so you don’t have to worry about any potential future costs. Furthermore, there are also grants available for solar batteries in the UK, helping you cut costs further.
As mentioned, the prices in the table above are simply an estimation and also don’t take installation costs or potential solar inverter costs into account. Installation costs can vary depending on factors such as the size of your battery and whether it’s AC- or DC-coupled.
Another thing to consider is that it is also usually more cost-effective to set up your solar battery system at the same time as installing solar panels.
If you’re interested in maximising your savings, then it’s a good idea to compare the total costs of installing different solar battery systems. This way you make sure you get the best deal. You can click the button below to compare up to 4 solar batteries from installers in your area without any obligation.
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Solar Panel Battery Storage: What Should You Consider?
Before you compare the specs of various solar batteries, it’s important to understand which specs you should pay close attention to and what exactly they all mean. Below, we’ve created a checklist of the most essential factors to consider when choosing a solar battery for your home:
- Battery size: A battery’s capacity size is the amount of electricity a battery is able to store. Battery size is measured in kilowatt-hours (kWh), therefore, it expresses how long a battery will be able to power your home for. In particular, you should look out for a battery’s “usable capacity”, as this tells you how much stored electricity you can actually access.
- Power rating: A battery’s power rating is expressed in kilowatts (kW) and tells you how many and what types of appliances you can power at once.
For example, a standard compact fluorescent lightbulb has a power rating of 0.012kW while a washing machine may have a power rating of 2.4kW. Therefore, your solar battery could sustain 20 light bulbs for much longer than just one washing machine.
Furthermore, solar batteries usually have two different power ratings: a continuous power rating and a peak power rating. The continuous power rating is the amount of electricity a battery can put out continuously for appliances that need a constant power supply. The peak power rating is the maximum amount of electricity a battery can release in a short burst, which helps certain appliances that need a burst of power to turn on.
- Round-Trip efficiency: As mentioned earlier, you can lose energy by converting it from DC to AC electricity and back. Therefore, round-trip efficiency measures how well your battery and inverter convert and store electricity. It specifically tells you the percentage of energy put into the storage that can be retrieved again.
- Depth of Discharge (DoD): This is the measure of a battery’s output relative to its capacity. Over time as batteries are used they lose their ability to hold charge. DoD is a calculation of the remaining charge hold.
This means that the full energy storage capacity the battery has at purchase will deplete over years of use. Therefore, when buying a solar battery it’s generally better to buy a battery with a higher DoD.
- Battery life-cycle and warranty: A battery’s life-cycle measures the number of times you can charge and discharge a battery before it loses performance. In regards to the warranty, some manufacturers, like Tesla, provide an unlimited cycle guarantee, however, most give a figure which can range from 1,800 to 10,000 cycles.
Furthermore, it’s important to check the details of a warranty. Many solar batteries will offer 10-year warranties, however, this doesn’t mean the same capacity is warrantied. For example, one battery might be warrantied to produce 70% of its original capacity over time, while another battery is only warrantied for 60%. Therefore, even though both batteries will still technically work for 10 years, the first battery will be able to store more electricity.
- Whether it works during power outages: If you live in an area where power cuts are commonplace, then it’s worth considering whether your solar battery can continue to function or not in these instances.
Certain batteries have no backup power and only work when the grid is available. Whereas other types of batteries will be able to continue to supply electricity to your home during power outages, as long as they have enough electricity stored. Solar batteries with full backup power tend to be more pricey, so this feature may only be worthwhile if you expect frequent outages.
Comparing Solar Batteries
Now that you know what to consider when researching solar batteries, it’s time to compare and contrast specific solar batteries to one another. Below we’ve summarised some of the top solar batteries currently on the market:
|Solar Battery||Usable Capacity (kWh)||Power Rating||Round-Trip Efficiency||Depth of Discharge (DoD)||Life Cycles||Warranty|
|Tesla Powerwall 2||13.5||10kW peak / 5.8kW continuous||90%||100%||Unlimited*||10 years|
|Powervault 3||4.1 – 20.5||6.6kW peak / 3.3kW continuous||N/A||100%||> 6,000||10 years|
|LG Chem Resu 10H||9.3||7.0kW peak / 5.0kW continuous||95%||95%||6,000||10 years|
|Enphase Encharge 10T||10.08||5.7 kVA / 3.84 kVA continuous||96%||80%||> 3,600||10 years|
|Varta Pulse 3 and 6||3.3 – 6.5||N/A||98%||90%||4,000||10 years|
* Within the warranty period
If you want to find out which solar batteries are available in your area and compare them more in depth, including price differences, then it’s a good idea to get in touch with professional installers. You can click on your region button below to compare up to 4 quotes from installers in your area, and thus find your ideal solar battery at the best price. It’s quick, completely free of charge, and you’re under no obligation.
Choosing the Best Solar Battery System
So now that you’ve started comparing solar battery systems, how do you choose the best one for your home? Below we’ve highlighted some of the most important factors as well as which batteries score best on them.
Solar Battery Storage Capacity
Choosing the solar battery with the best storage capacity isn’t simply a case of choosing the battery with the largest capacity. You need to consider how much electricity you use daily and how much you want to have readily available on days where your solar panels aren’t generating enough energy or perhaps when there’s a power cut.
The average home in the UK consumes between 8kWh and 10kWh daily. However, if you live in a home with 3+ people or if you frequently use appliances that require a lot of power then your consumption may be significantly higher. Therefore, it’s also a good idea to look at your previous energy consumption to gain more clarity on what size of solar battery you’ll need.
If you require a high amount of storage capacity, then the Powervault 3 is an excellent choice as it’s available in an impressive 20kWh. However, naturally the higher the storage capacity the higher the price, so it’s important to consider what you actually need so you don’t spend extra money unnecessarily.
It’s also useful to know that most solar batteries are stackable. Therefore, you can combine multiple batteries to get the exact storage capacity you need.
When choosing the best battery based on its number of life-cycles within the warranty period, you may think that going with a battery that guarantees 6,000+ or even unlimited cycles is the best option. While this is usually a good choice as it indicates a longer lifespan, it doesn’t necessarily mean it’s the best.
This is because a battery’s life-cycle says nothing about how its capacity will decline over time. For example, if we have a 10kWh battery with 5,000 cycles, the first thousand cycles of the battery’s life will likely effectively deliver all 10kWh of energy to your home (minus inefficiencies), while the last thousand will probably not be so effective. The battery may only be able to store 50%, or 5kWh, at this point.
Furthermore, unless the manufacturer specifically says in the product’s warranty, it’s also difficult to know how quickly this decline may happen.
Therefore, buying a solar battery with a higher number of cycles is probably a good idea, however you should also consider the Depth of Discharge and warranty length. This will give you a sense of peace as to how the battery will perform over time.
Solar Battery Companies
There are some great companies creating solar batteries for the UK market. Below we’ve listed some of the most renowned manufacturers globally:
We’ll start the list off with Powervault, a British company that began in 2012. Its mission is to lower people’s electricity bills alongside their carbon footprint. There are two main advantages of installing a Powervault 3. Firstly, because they are UK-based their customer service is more hands-on and timely. Secondly, you can earn money through using their GridFlex platform.
Tesla is a household name due to the popularity of their electric vehicles and solar technology. They are known for their quality, reliability, and sleek design. A fantastic benefit to Tesla’s Powerwall 2 is that you can be 100% independent from the grid, as it can still function during power outages.
LG is another household name. They are primarily known for their TVs and laptops but their expertise also extends to solar systems. Their solar panels have even won the Intersolar AWARD 3 times. Benefits of their LG Chem battery include battery backup for during power cuts and being more compact in size compared to competitors.
Enphase is a California-based company with over 15 years of experience in the field of home energy. Their solar batteries are outdoor rated, as they are made to withstand extreme temperatures and humidity. Furthermore, they’re known for their emphasis on smart technology and intuitive design.
Varta is a German company that was established over 130 years ago. Therefore, they know a thing or two when it comes to batteries. Their energy storage systems have been voted the best energy product of the year in the haustec.de readers’ poll. Another plus to their energy storage systems is that customers can easily expand their storage capacity at any time, even after installation.
However, these are not the only top companies available on the UK market. To see which brands are available to you click the button below to receive up to 4 no-obligation quotes and compare the best deals between companies.
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Lithium ion batteries are usually the best choice for a solar panel system, as they have a higher discharge rate and longer lifespan compared to other battery types. For example, lithium ion batteries usually have a discharge rate of 70-90% while lead acid batteries only discharge around 50%. Furthermore, their lifespan is typically more than double that of lead acid batteries.
Brands such as Tesla and LG Chem provide lithium ion batteries. However, one thing to keep in mind is that other battery types are likely more affordable.
Like how many solar panels you need, how many solar batteries you need depends on your home’s energy needs. The typical UK home consumes between 8kWh and 10kWh a day. However, depending on your consumption habits or if you have 3+ people living in your home then this can be higher.
Therefore, it’s advisable to review your previous energy consumption and base the size of battery you’ll need off of that.
Lithium ion batteries generally last the longest compared to other battery types. For example, their lifespan is more than double that of lead acid batteries. Another advantage to lithium ion batteries is that they tend to have a larger capacity, meaning you can store more electricity for your home.
Brands such as LG Chem and Tesla produce lithium ion batteries. However, one thing to keep in mind is that these advantages come at a price point.
The most suitable battery for off-grid system application will depend on your needs. There are 3 types of batteries you should consider – lithium ion, flooded, and absorbed glass mat (AGM). The last two types are both lead acid batteries.
Lithium ion batteries perform well overall, and can save you electricity, time and money. They also require less maintenance compared to the other battery types. However, two things to consider are that they are the most expensive option and can stop working below 0°C.
AGM batteries are more affordable and are considered suitable for high short-term power applications. Flooded batteries, on the other hand, offer large storage capacity for backup power at the cheapest price. However, flooded batteries should only be installed outdoors as they emit gases which can be explosive and toxic.