Solar battery storage is becoming an increasingly important tool for homeowners who are looking to reduce their bills and maximise the solar energy they generate. As the technology has developed over the last few years, storage batteries will play a central role in creating more sustainable homes of the future.
This comprehensive guide is your one-stop shop for information and knowledge on solar battery storage. We cover all of the key areas from what battery storage is and how it works to how much the cost and, more importantly, how much you can save.
Understanding solar energy and battery storage
Before we head into some of the finer details of solar battery storage, it’s always a good idea to cover the basics of how solar energy works and the role that battery storage plays in solar energy systems.
What is battery storage?
Battery energy storage systems, sometimes known as BESS, allows you as a homeowner to store excess electricity generated by your solar panels. This stored solar energy can then be used during periods when your solar panels are not generating enough power, such as at night or on cloudy days.
By storing and using your own generated electricity, you reduce your reliance on the grid and lower your energy bills – this is because you’ll be harnessing more of the ‘free’ energy you generated from your solar panels.
How does battery storage work?
Solar panels generate electricity through a process called the photovoltaic effect. When sunlight hits the solar panels, it excites electrons within the panel’s cells, causing them to move and generate direct current (DC) electricity.
This DC electricity is then sent to an inverter, which converts it to alternating current (AC) electricity. This is the type of electricity that’s used by your home appliances and the national grid.
In a solar energy system with battery storage, any excess electricity that isn’t immediately used by your home is sent to the battery storage system instead of being fed into the grid. If your battery is already full, the third stop for your solar energy will be the national grid.
Alongside the main battery and the inverter, you’ll have a Battery management system or control centre. This is the brains behind the battery, monitoring and controlling the charging and discharging, as well as where the energy goes. You can find more info on getting started with battery storage.
Why are BESS important for green energy and more sustainable living?
Battery storage is set to play a crucial role in the transition to green energy and sustainable living. By storing excess solar energy, which is clearly abundant, battery storage systems help to maximise the use of renewable energy. In turn this reduces our reliance on fossil fuel-generated electricity from the grid.
This not only lowers your carbon footprint but also contributes to a more stable and resilient energy grid. As more households adopt solar battery storage, the collective impact on reducing greenhouse gas emissions and mitigating climate change becomes significant.
On a wider scale, the adoption of BESS is central to achieving net zero emissions by 2050. The use of battery storage is growing at a phenomenal rate. Currently there’s 3.5GW of battery storage capacity in the UK, but there’s a goal of hitting 30GW of storage by 2030. Read more on the current capacity of UK BESS here.
Types of solar battery storage systems
Before diving into the specific battery technologies, there are two main categories of BESS projects:
- Front-of-the-metre (FOM)
FOM BESS projects, also known as grid-scale or utility-scale storage, are connected directly to the electricity grid. They’re typically owned and operated by utilities or independent power producers. These large-scale projects are designed to provide various grid services, such as ‘peak shaving’ and renewable energy integration. FOM projects are usually larger than 1 megawatt (MW) in capacity and can go up to several gigawatts (GW).
- Behind-the-metre (BTM)
BTM BESS projects are installed on the customer’s side of the electricity metre and are smaller in scale compared to FOM projects. BTM projects cover residential, commercial and industrial settings.
BTM systems can range from a few kilowatts (kW) to several MW in capacity, depending on the setting and needs the battery is serving.
Almost all new BTM BESS projects, whether it’s residential or industrial, use lithium-ion as the main types of storage battery technology.
Main storage battery types
Lithium-ion batteries have become the dominant choice for residential solar battery storage thanks to their high energy density, long lifespan, low maintenance and decreasing costs. Over the last 5-10 years, their market share has grown exponentially compared to the previous favourite, lead-acid batteries.
Within the lithium-ion battery category, there are a couple of different chemistry types. You have lithium iron phosphate (LFP or LiFePo4) batteries and nickel manganese cobalt (NMC) batteries.
Lead-acid batteries have been used in off-grid solar systems for decades due to their affordability and reliability. They have lower costs than lithium-ion batteries, but they have more disadvantages, including lower energy density, a shorter lifespan of around five years and require regular maintenance.
Flow batteries are an emerging technology that’s primarily used in large-scale energy storage projects. Lasting for several decades, flow batteries store energy in a liquid electrolyte solution, which allows for easier scaling of storage capacity. The downside is that they take up a lot of space, come with a more complex system and have higher upfront costs.
Benefits of solar battery storage
For homeowners, there are plenty of reasons to invest in solar battery storage. Here’s a look at some of the main benefits:
- Maximise your solar energy – Generating your own solar energy is one of the cheapest forms of electricity you can get. By storing excess solar energy generated during the day, you can use more of your own clean energy, even when the sun isn’t shining. This saves you from tapping into and relying on the grid, especially during peak hours when energy prices are highest.
- Lowering electricity bills – By using stored, cheap solar energy instead of drawing from the grid, you automatically reduce your electricity bills. The extent of these savings will depend on a variety of factors, including your energy consumption patterns, battery capacity and local electricity rates.
- Providing backup power – In the event of a power cut, a solar battery storage system can provide emergency backup power. Depending on the size of your battery, this should keep all of your essential appliances and devices running. This is particularly valuable to homes in areas prone to frequent power cuts.
- Contributing to a cleaner environment – By maximising the use of clean, renewable energy from your solar panels and minimising your reliance on fossil fuel-generated electricity, you’re actively contributing to reducing greenhouse gas emissions from entering the atmosphere and playing your part for the planet.
Read more details about the benefits of solar battery storage.
What size solar battery system do you need?
Ok, you’ve heard about the types and the benefits associated with solar battery storage, but how do you work out what size battery system you need?
Determining the right size for your solar battery storage system is a crucial step if you care about efficiency – which we all should. The right size battery means your energy needs will be met and you’ll be able to reap the extra benefits. An oversized or under-sized storage battery will see both your cost-effectiveness and energy-effectiveness reduced.
Here are a few factors to bear in mind when sizing your battery system:
- Assessing your energy needs and consumption patterns
The first thing you need to understand is your household’s energy consumption patterns. This involves looking at your electricity bills and identifying your average daily, weekly and monthly energy usage. Pay special attention to your consumption during peak hours, as this is when you’ll likely rely on your stored solar energy the most. If you have solar panels installed already, you’ll want to see how much energy you’re currently exporting to the grid. This will give you a good understanding of how much you might be able to send to your battery instead.
- Determining the right battery capacity
Once you have a clear understanding of your energy needs, you can determine the optimal battery capacity for your home. As a general rule of thumb, you’ll want a battery capacity that can cover your essential energy needs during periods when your solar panels are not generating sufficient power. It’s always better to slightly oversize the battery than go under.
When looking at storage batteries, consider factors such as usable capacity, depth of discharge (DoD), usable capacity and power output.
Usable capacity tells you exactly how much energy you can store and use. It’s a more accurate figure than total capacity, which doesn’t take into account the energy required to power the battery itself. You may also read about ‘round-trip efficiency’ which indicates the amount of energy that can be retrieved from the battery compared to the amount of energy put in.
DoD refers to the percentage of the battery’s capacity that can be safely used without damaging the battery. A higher DoD allows you to use more of your battery’s storage potential. A lot of good quality, modern batteries have 100% DoD. Round-trip efficiency.
Power output determines the maximum amount of energy the battery can deliver at one time. This is important if you tend to run multiple high-energy appliances, such as electric heating and tumble driers, at one time.
Of course, it’s always a good idea to get a professional installer involved who can advise you accordingly. There’s plenty more information on calculating the size of your solar battery storage system here.
Can battery storage power a house?
Battery storage can significantly reduce your reliance on the grid. There’s no doubt about this. But can it power your whole house and effectively let you go off-grid?
The extent to which a battery storage system can power your house depends on several factors, like your energy consumption, battery capacity and the duration you’d be using the battery for. For example, if your home uses roughly 10kWh of electricity a day and you have a battery storage with 10kWh capacity, you’d expect it to be able to power your home for around a day.
In most cases, a standard residential battery storage system will be designed to cover your essential energy needs during periods when your solar panels are not generating sufficient power. This typically includes powering appliances such as your fridge, lights and electronic devices. But it’s important to have realistic expectations about its ability to power your entire home.
Running energy-intensive appliances like electric heating systems, washing machines and electric vehicle chargers for extended periods will quickly drain your battery. Also powering multiple devices at once will use more energy.
It’s also important to consider seasonal variations in solar energy production. During the winter months, when solar panels generate less electricity, your battery storage system may not be able to fully power your home for long periods without additional charging from the grid. However, in the height of those long summer days when you’re using less energy, your home may be able to go off-grid for multiple days in a row.
Find out more info on whether battery storage can power a house here.
Can you have battery storage without solar panels?
The vast majority of residential storage batteries are either installed with solar panels or added to existing solar set up. But is it possible to have battery storage without solar panels?
Yes, it is. Without solar panels, the battery storage system is charged using electricity from the grid. This is typically done during off-peak hours when energy prices are lower. The main benefit of having battery storage without solar panels is the ability to take advantage of time-of-use electricity tariffs. By charging your battery during off-peak hours and using the stored energy during peak hours when electricity prices are higher, you can potentially reduce your energy bills.
However, it’s important to note that without solar panels, you won’t be able to generate your own clean energy. This means your battery storage system will still rely on electricity from the grid.
Overall, it’s likely that your environmental impact won’t be reduced and it’ll take you much longer to see a payback and return on your investment than if you had battery storage with solar panels.
Is it better to have more batteries or more solar panels?
So we know it’s most effective to have battery storage and solar panels together, but what’s it best to have more of?
The answer depends on your specific energy needs, so let us explain.
If your primary aim is to maximise your energy independence and have a reliable backup energy source during power cuts, investing in more batteries may be the better option. With a larger battery capacity, you can store more excess solar energy and have a longer supply of backup power.
On the other hand, if your aim is to generate more clean energy and potentially export excess electricity to the grid for additional income, installing more solar panels may be the way to go. More solar panels equals a higher electricity generation capacity, which can lead to greater cost savings and environmental benefits over time.
That said, the best approach is to strike a balance between your solar panel and battery storage capacities based on your energy consumption patterns, budget and long-term goals.
Battery storage costs and savings
Investing in a solar battery storage system can eventually provide significant long-term financial benefits. But it’s essential to understand the costs and potential savings involved from the outset to give you realistic expectations.
How much do solar battery storage systems cost?
The cost of a solar battery storage system can range widely depending on factors such as the battery capacity, the brand and installation.
On average, homeowners can expect to pay between £4,000 and £8,000 for a standard residential battery storage system. However, prices can range from around £2,500 for a small, entry-level system to over £10,000 for a high-capacity, premium setup.
For example, prices for the 13.5kWh Tesla Powerwall 2 start from around £5,800, which is good value. The stackable Huawei Luna battery comes in around £6,000 for a 10kWh set up.
You also have to account for installation costs. On average, homeowners can expect to pay anywhere between £500 to £2,000 for the installation labour, in addition to the cost of the battery storage system itself. This differs depending on how long the installation takes and how complicated it is.
It’s important to work with a reputable and experienced installer who can assess your specific needs and provide a detailed quote for the installation. They can also advise you on any necessary electrical upgrades or permissions required for your battery storage system.
How much can you save with solar battery storage?
The potential savings from a solar battery storage system also depend on various factors, such as energy consumption patterns, local electricity rates and the size of your system.
On average, households with a well-designed solar panel and battery storage system can expect to save between 60-80% on their annual electricity bills. This saving can be around £1,000 a more in some circumstances.
Let’s say you’re saving £1,000 a year and your system costs £6,000, it’ll take you six years to break even. Typically, a payback period ranges from 6 to 12 years.
Either way, from the point you break even, you’ll be seeing a return on your investment. Over the lifetime of your system (usually 10-15 years for batteries and 25+ years for solar panels), you can save thousands and thousands of pounds on your electricity bills, whilst generating clean, green energy.
Learn more details about cost savings with solar battery storage.
Selling electricity back to the grid with battery storage
One of the added benefits of having a solar battery storage system is the ability to sell excess electricity back to the grid through the Smart Export Guarantee (SEG) scheme.
By exporting excess energy to the grid during peak hours when demand and prices are higher, you can maximise your SEG income and further improve your system’s financial return.
It’s important to note that the specific rates and terms of SEG payments will vary depending on your electricity provider and tariff. Some providers offer more attractive rates for homes with battery storage, so it’s worth shopping around to find the best deal.
Octopus Energy are one of the best providers for this. For example, if I was signed up to Octopus’ Intelligent Flux tariff, I’d get a peak export rate of 29.6p per kWh and an off-peak export rate of 22.2p per kWh. Pretty good rates by all accounts. Read more on selling electricity back to the grid here.
Available storage battery incentives
Currently, there are no direct grants specifically for solar battery storage systems in the UK. The main incentive is a VAT reduction, which came into place at the start of 2024. With this, battery storage systems are eligible for the 0% VAT rate when installed on their own or alongside a new solar panel system.
Solar battery installation
There are three main scenarios for installing a solar battery storage system:
- Installing battery storage with new solar panels – This is the most straightforward and cost-effective option, as the battery storage system can be smoothly integrated with the new solar panel setup. This allows for optimal system design and compatibility from the outset.
- Adding battery storage to an existing solar panel system – If you already have solar panels installed, you can retrofit a battery storage system to improve your panel’s efficiency and overall savings. Depending on your setup, retrofitting may involve an inverter upgrade to make sure everything is compatible.
- Installing battery storage without solar panels – This is the least common scenario, but it is possible to install a battery storage system without solar panels. This is straightforward for a professional installer with the battery needing a connection to your home and the grid. It’s possible to retrofit solar panels onto this setup at a later date.
How big are battery storage systems?
On average, a battery storage unit ranges from the size of a small suitcase to a large fridge-freezer.
For example, a 6kWh may have dimensions in the range of:
- Height: 65cm – 120cm
- Width: 45cm – 85cm
- Depth: 12cm – 30cm
Before installing, it’s important to consider the available space in your home. Storage batteries will need a dedicated space or area, giving the battery space and control system space for ventilation and access for any maintenance. Ideal spots are loft spaces and utility rooms, which are cool and dry.
Read more on battery storage dimensions here.
Warranty and lifespan
On average, lithium-ion batteries used in residential applications can last between 10-15 years before needing replacement.
Most residential battery storage systems come with a warranty of at least 10 years. This is the minimum you should look for.
Some batteries have longer warranties. The GivEnergy All in One has a 12 year warranty whereas the Enphase IQ comes with a 15 year warranty. Sometimes it’s possible to buy longer warranties from the battery seller.
It’s important to read the conditions or limitations associated with the warranty. For example, some have a maximum number of charge cycles they guarantee for. Other good warranties will guarantee efficiency figures after so many years, meaning you won’t be stuck with an inefficient battery. Learn more about battery storage life expectancies and warranties here.
Recycling your storage battery
Although batteries have only just started to become popular, recycling and end-of-life management still need to be considered. Proper recycling not only helps to conserve valuable resources but also prevents potential environmental harm from improper disposal.
Currently, the recycling infrastructure in the UK for lithium-ion batteries is limited. However, the government and industry are working to establish more comprehensive recycling programmes and regulations to ensure the sustainable management of battery waste.
Some battery manufacturers, such as Tesla, have their own recycling initiatives or partnerships with specialised recycling companies. These programmes aim to recover valuable materials such as lithium, cobalt and nickel from used batteries, which can then be used in the production of new batteries or other products.
What are the best battery storage systems?
When it comes to choosing the best battery storage system for your home, there’s a good amount of choice out there. Some of the factors you want to keep in mind are battery capacity, depth of discharge, price and warranty.
Some of the our favourite battery storage options are:
- Tesla Powerwall – The Tesla Powerwall 2 is one of the most popular and well-known residential battery storage systems, offering a high capacity of 13.5 kWh and a 10-year warranty. It features advanced NMC lithium-ion technology and integrates with the Tesla app for easy monitoring and control.
- GivEnergy All-inOne – The GivEnergy All-in-One comes with a 13.5kWh capacity as standard from a single battery. It’s super efficient and utilises LFP technology.
- Huawei Luna – The Huawei Luna is a modular battery that’s highly stackable. It comes in 5kWh batteries that can be set up in parallel to give you extra capacity. This battery has a 100% depth of discharge and uses LFP technology.
- SonnenBatterie 10 – German-engineered SonnenBatterie are known for their high efficiency and intelligent energy management features. The SonnenBatterie 10 series offers capacities ranging from 2 kWh to 16 kWh, with a lifespan of up to 10,000 charge cycles.
- Powervault P4 – Powervault is a British manufacturer of home battery storage systems, offering capacities ranging from 8kWh to 16kWh. The Powervault P4 features a modular design, allowing for easy expansion as your energy needs grow.
What does the future look like for solar battery storage?
- Emerging technologies in solar battery storage
- Trends and projections for adoption and growth
- Potential impact on the energy sector and sustainability goals
With ongoing advancements in technology, falling costs and an increasing number of instalments in homes, the future of solar battery storage looks promising.
The UK and global solar battery storage market has already experienced quick growth. From 2022 to 2023, the UK witnessed an 68% increase in planned battery storage project work. This rapid growth is expected to accelerate significantly more in the coming years, with UK battery storage capacity set to increase 9-fold by the end of the decade. Read more on battery storage market trends.
As the UK continues to transition towards a cleaner, more sustainable energy future and aims to hit net zero targets by 2050, battery storage will play a central role in allowing the widespread integration of renewable energy sources. The growth of the battery storage industry is expected to create new jobs and economic opportunities, contributing to the development of a much-needed green economy.
