How Does Solar Battery Storage Work?

Over the last few years, solar battery storage systems have continued to gain popularity with homeowners looking to get away from ever increasing energy bills and increase their use of clean, renewable energy. 

With the shift towards renewable energy sources well underway, it’s important to improve your understanding on how certain systems work, so that you can make the most of them. With their use increasing, understanding how solar battery storage works is a beneficial move. 

This article will provide an in-depth look at the fundamentals of solar battery storage systems, their components and how they integrate with solar panels to create a more efficient and sustainable energy solution for your home. The aim is to give you a clear understanding of the benefits and considerations involved in investing in a solar battery storage system. 

What is solar battery storage?

A solar battery storage system is an energy solution that stores the excess electricity generated by your solar panels for later use. They’re sometimes known as battery energy storage systems, or BESS for short. 

In simple terms, these clever systems are made up of three main components:

• • A battery (usually lithium-ion)

• • An inverter

• • A control system

The battery is the part that stores electrical energy in chemical form until it’s needed. The inverter is responsible for converting the direct current (DC) electricity generated by your solar panels and stored in the battery into alternating current (AC) electricity, which is used to power your home appliances. 

And finally, the control system monitors energy production, consumption and grid connection to optimise the battery’s charging and discharging cycles. You can read more on the basics of home battery storage here.

Types of solar battery storage systems

When it comes to BESS, there are three main types of storage batteries:

• • Lithium-ion

• • Lead-acid

• • Flow batteries

For the purposes of residential solar energy storage, lithium-ion batteries have become the dominant choice. This is because they have high energy density (they don’t take up a lot of physical space for the amount of energy they can store), they have a long lifespan and low maintenance requirements. 

Lithium-ion batteries also have a high depth of discharge (DoD), meaning they can be discharged more fully without damaging the battery’s long-term performance. You can now get lithium-ion batteries with 90%+ DoD. 

The two most common subt-ypes of lithium-ion batteries used in solar storage systems are nickel manganese cobalt (NMC) and lithium iron phosphate (LiFePO4).

Although more affordable, lead-acid batteries use old technology. They’ve now largely been phased out as they have a lower energy density, shorter lifespan and require more maintenance compared to their lithium-ion counterparts.

Flow batteries are a newer technology primarily used in large-scale utility projects. These batteries store energy in liquid electrolytes, making them highly scalable and suitable for long-duration energy storage. However, flow batteries have a lower energy density and higher cost compared to lithium-ion batteries, making them less practical for residential applications. Read more about storing commercial energy here. 

How battery storage works with solar panels

Focussing on a residential setting, when your solar panels generate more electricity than your home needs at that moment, the excess energy is sent to the battery for storage instead of being fed back into the grid. 

This stored energy can then be used during periods of low or no sunlight, such as at night or on cloudy days. The battery reduces your dependence on the grid and maximises  the use of your solar-generated electricity – the cheapest form of electricity that you can come across. 

By integrating smart software and control systems, solar battery storage systems can optimise energy distribution based on real-time demand and supply conditions. So, if you’re looking to run an energy efficient home, solar battery storage should be an integral part.

It’s possible to use a battery without solar panels too. In this instance, the battery would draw cheaper energy overnight to use during the day when prices are higher. For this to work effectively, you need to be on a good time of use tariff. However, it’s not the most efficient way to use battery storage – that’s certainly in combination with solar panels. 

Benefits of solar battery storage

Investing in a solar battery storage system offers plenty of benefits for homeowners.

One of the primary advantages of solar battery storage is its ability to maximise the consumption of your own solar-generated electricity. By storing excess energy during peak sunlight hours, you can use this stored energy later when your solar panels are not generating enough power to meet household demand. This effectively reduces your reliance on the grid during peak hours when electricity prices can be around 25-30p per kWh. With the average house using 9.5kWh per day, this cost quickly adds up. 

This leads to another significant benefit – lower electricity bills. By using stored solar energy instead of drawing from the grid during peak hours, you can significantly reduce your energy costs over time. Additionally, if your battery system is connected to the grid, you may be eligible for feed-in tariffs, which allow you to sell excess electricity back to the grid. This is great as it further offsets your electricity expenses and the cost of installing battery storage in the first place. 

Solar battery storage systems also provide a reliable backup power source during emergencies. In the event of a power cut, your battery system can continue to power your essential appliances and devices. This gives you a level of energy security and independence.

Another benefit worth mentioning here is that solar battery storage helps increase the use of clean, renewable energy from your solar panels. This is brilliant as it minimises your reliance on grid electricity, of which a large part is still generated from the burning of fossil fuels. So, battery storage can help you to reduce your carbon footprint.

You can read more information in our post on the 10 benefits of solar battery storage. 

What to consider when choosing a solar battery storage system

When choosing a solar battery system for your home, there are several important factors you’ll want to consider to make sure you invest in the most suitable and cost-effective solution.

Firstly, you’ll want to make sure you get the right size battery. Doing this involves evaluating your household’s energy consumption patterns and the capacity of your solar panel system. This will help you determine the optimal battery capacity and power output required to meet your energy needs. 

A battery’s capacity is measured in kilowatt-hours (kWh), whilst its power output is measured in kilowatts (kW). A higher capacity battery will store more energy, whilst a higher power output allows for more appliances to be powered simultaneously.

Another essential factor to consider is the battery’s depth of discharge (DoD). This refers to the percentage of the battery’s total capacity that can be safely used without deteriorating the battery lifespan. A higher DoD allows for more of the battery’s capacity to be used, which makes the system more cost-effective.

It’s also wise to consider the available space for installation and your budget. Lithium-ion batteries are more compact and don’t take up too much space, although you will need a dedicated space – read more details here on how big are battery storage systems. 

These batteries also have a longer lifespan but come with a higher upfront cost compared to lead-acid batteries. Evaluate the long-term cost-effectiveness of the system, taking into account potential energy savings and the battery’s expected lifespan.

What about installing solar battery systems?

If you already have solar panels and are wanting to retrofit battery storage, you’ll want to make sure that everything is compatible. 

Solar battery storage systems can be integrated using either AC or DC coupling. AC-coupled systems are generally easier to retrofit into existing solar panel setups, as they connect to your home’s electrical system after the solar inverter. This means you can use your existing solar inverter and install a separate inverter for the battery, making the installation process less complex.

DC-coupled systems are more efficient but may require modifications to your current configuration. You may be required to replace your existing solar inverter with a hybrid inverter that can handle both the solar panels and the battery. This option is more suitable if you’re installing a new solar panel system along with battery storage or if your current inverter is nearing the end of its lifespan.

Your installer should assess your current setup and recommend the most suitable configuration for your needs. Check out this post on how to add battery storage to a solar system.

Sizing a solar battery storage system

Properly sizing your solar battery storage system is a crucial step to make sure your energy needs are met and the return on your investment is maximised. The process involves assessing your household energy consumption, evaluating your solar energy generation and calculating the optimal battery size capacity for your home.

To work out your energy consumption, start by reviewing your electricity bills as these provide a breakdown of your usage over a given period. You can also use a home energy monitor to track your real-time consumption and identify peak usage times. It’s essential to consider the power ratings of your appliances and any potential future changes in your energy needs, such as the addition of an electric vehicle or home expansion.

If you have an existing solar panel system, evaluate its energy generation by taking a look at your system’s data. This will give you an accurate picture of how much energy your panels produce daily, as well as how much is exported, helping you determine the excess energy available for storage.

Once you have a clear understanding of your energy consumption and generation, you can calculate the optimal battery capacity for your needs. A simple formula to estimate the required capacity is: Battery capacity (kWh) = Daily energy consumption (kWh) – Daily solar energy generation (kWh). 

For example, if your household consumes 20kWh of electricity per day and your solar panels generate 15kWh, you would need a battery with a capacity of approximately 5kWh to cover the difference.

In general, it’s better to slightly oversize your battery system to make sure it can meet your energy needs during periods of low solar generation or unexpected increases in consumption.

To give a further example. Imagine a family of four living in a medium-sized home with a 5kW solar panel system consumes an average of 12kWh of electricity per day. Their solar panels generate an average of 16kWh per day. To maximise their energy independence and reduce monthly energy bills, they go for a 8kWh lithium-ion battery, so they can store excess solar energy during the day and use it to power their home during evening hours.

Lifespan of battery storage systems

When investing in a battery storage system, it’s key to consider the lifespan and potential maintenance requirements to make the most from your investment.

The average lifespan of a lithium-ion battery is between 10 and 15 years. However, this expectancy can be influenced by a few different factors, including:

• • Battery type – Different battery chemistries and manufacturing processes can impact a battery’s longevity. Lithium iron phosphate (LiFePO4) batteries, for example, tend to have a longer lifespan compared to other lithium-ion variants.

• • Depth of Discharge – A higher DoD means the battery can be discharged more fully without negatively impacting its lifespan. Modern lithium-ion batteries typically have a DoD of 80% or higher, allowing for more of the battery’s capacity to be used. The higher the better.

• • Environmental conditions – Extreme temperatures can affect a battery’s performance and lifespan. All batteries should be installed in a cool, dry and well-ventilated area to minimise the impact of environmental factors.

• • Maintenance – Although lithium-ion batteries require relatively little maintenance compared to other battery types, it’s still important that you follow the manufacturer’s recommendations for care and upkeep. This may include regular cleaning, inspection for signs of damage or wear and monitoring the battery’s performance using the provided software or app.

To maximise your solar battery storage system’s lifespan, consider the following tips:

• • Go for a high-quality battery from a reputable manufacturer

• • Install the battery in a suitable location, away from direct sunlight and extreme temperatures.

• • Follow the manufacturer’s guidelines for charging and discharging the battery and avoid regularly depleting the battery below its recommended DoD.

Most solar battery storage system manufacturers will offer warranties that cover the battery for a specific number of years or charge cycles. These warranties typically range from 6,000 to 10,000 cycles. Be sure to review the warranty terms to understand what you’re covered for and for how long.

Cost and savings with battery storage

One of the most important factors to consider when investing in a solar battery storage system is the upfront cost and potential long-term savings. For most householders, it ultimately comes down to finances no matter how good the environmental intentions are.

The cost of a residential battery storage system can vary significantly depending on factors such as the battery’s capacity, brand and installation costs.

On average, a solar battery storage system in the UK can cost between £2,500 and £10,000, with larger capacity systems and premium brands falling on the higher end of the price range. Whilst this initial investment is a lot, you need to consider the potential long-term savings and benefits. 

It’s thought that solar panels alongside battery storage can reduce your annual electricity bill by 70-80%! The exact amount of money you can save with a solar battery storage system depends on several factors, including:

1. 1. Battery capacity and performance – A larger capacity battery with a high DoD will allow you to store and use more solar-generated energy, reducing your reliance on the grid and lowering your electricity bills.

1. 1. Household energy consumption patterns – The more energy you consume during peak hours (when electricity prices are higher), the more you can save by using stored solar energy instead of drawing from the grid.

1. 1. Electricity tariffs – If you’re on a time-of-use tariff, you can take advantage of lower off-peak rates to charge your battery and use the stored energy during peak hours when rates are higher.

1. 1. Presence of solar panels – If you have a solar panel system, a battery storage system will help you maximise the use of your solar-generated electricity, further reducing your reliance on the grid and increasing your savings.

Let’s take a look at a quick example.

A family with a 4kWh solar panel system and an average daily energy consumption of 12kWh invests in a 6kWh lithium-ion battery storage system. The battery allows them to store excess solar energy generated during the day and use it during peak evening hours. By reducing their reliance on the grid during high-cost periods, they can save approximately £500 per year on their electricity bills.

Over a 10-year battery lifespan, the family’s total savings would amount to around £5,000. Considering the upfront cost of the battery system (approximately £4,000), the net savings would be £1,000, with the system paying for itself after 8 years. However, if the battery continues to work effectively for another five years, that’s all free energy! 

It’s important to note that these figures are just an example, and actual savings will vary depending on your specific circumstances. As battery technology continues to advance and costs decline, the long-term financial benefits of solar battery storage systems are expected to increase. This makes them an increasingly attractive investment for homeowners looking to reduce their energy costs and carbon footprint.

Here at Eco Affect, we believe that battery systems will continue to become more accessible and cost-effective for homeowners.

In the coming years, we expect to see continued improvements in battery capacity, efficiency and lifespan, as well as the development of new battery chemistries and designs. These advancements will further reduce the upfront costs of solar battery storage systems and increase their long-term financial benefits.

As this happens, we hope that governments and energy companies recognise the importance of distributed energy storage in creating a more resilient and sustainable energy grid. If this happens, we may see the introduction of new incentives and policies that encourage the adoption of residential battery storage systems.

For homeowners considering investing in a solar battery storage system, now is an excellent time to explore your options. By understanding how these systems work, their benefits and the factors to consider when choosing a system, you can make an informed decision that will help you reduce your energy costs and contribute to a cleaner, more sustainable future.