How to Add Battery Storage to a Solar System

How to Add Battery Storage to a Solar System

In the last few years the adoption of battery storage for residential solar systems has seen a big increase. Historically, storage batteries were only really practical for off-grid type installations. They just weren’t a consideration for standard homeowners. 

However, just as solar panel prices have experienced a dramatic decrease over the past decade, battery prices have followed suit. This has been the main driver, alongside the green energy advantages they bring. 

What’s even better, as the prices have dropped, batteries have become more advanced and efficient. As a result, we’ve seen battery storage become an increasingly attractive option for many grid-tied solar systems. 

So, if you find that your solar panels are generating a substantial amount of energy when you’re not home, and most of it is being sent to the national grid, it may be time to consider adding battery storage to your solar system. This article will bring you up to speed on the process of adding a new battery system into your existing solar setup.

Why add battery storage to your solar panels?

Adding solar battery storage into your home’s energy system can be a huge step in revolutionising the way you capture and use the power generated by your own PV panels. Yes solar panels have advantages with or without battery storage, but incorporating solar battery storage really helps to maximise your energy savings. 

The most cost-effective electricity is the energy you generate yourself. By storing excess energy produced by your solar panels during high sunlight hours, you can avoid feeding it back into the grid or selling it at a lower price than what you’d have to buy the electricity back at. Without a battery, any surplus energy your home produces is essentially wasted for you.

Whilst there’s a sizable upfront cost to solar storage batteries, the long-term financial benefits make it a smart investment. 

Alongside making the most of your own solar power, batteries give you more energy independence, help to lower your monthly bills, store cheap energy, contribute to a cleaner environment and prepare your home for what’s coming in the future. You can read up on more reasons you should get battery storage here. 

Can I add battery storage to my existing solar system?

Yes, you can certainly add battery storage to your existing solar system. Just how simple or straightforward this is depends on your current setup. It all comes down to the inverter. 

Just as not all phone chargers work for every mobile, not every solar battery works with every solar panel inverter. So, there may be a bit of rejigging here and swapping of inverters. However, the main thing is that a solution is possible. 

When selecting a battery, you’ll also have to consider other factors such as the best capacity for your home, the desired depth of discharge (the higher the better) and warranty periods. For example, choosing a battery with a high DoD and an extended warranty will help optimise your system performance and longevity, making the most of your investment.

What’s the best integration method for battery storage on a solar system?

This is the crucial question when adding battery storage to a solar panel system. And it comes down to two main options: an AC-coupled system or DC-coupled system. 

The decision isn’t straightforward and hinges on a few factors. If you’re not fully clued up on how solar is sent to the battery, have a read here on the basics of home battery storage

AC-coupled systems 

AC-coupled systems integrate the battery into the main AC circuit, which comes after the solar inverter. This approach is the most straightforward way to retrofit a battery into an existing solar set-up, particularly if your inverter is older. 

In this configuration, a separate inverter is used to charge the battery. The inverter converts the DC power from your panels to AC power, which is then directed to your home to power your appliances or sent to the grid. This is based on your energy consumption and the battery’s charge status. 

AC-coupled systems are generally easier to install, provide flexibility in terms of placement, and are compatible with a range of inverters. However, they are slightly less efficient due to the multiple power conversions involved.

DC-coupled systems

On the other side, DC-coupled systems connect the battery directly to the solar panel’s DC output. This comes before the inverter. 

This setup is typically more efficient as it minimises energy losses during the conversion process. If you have this configuration with your current solar panels, your existing solar inverter will be replaced with a hybrid inverter that’s compatible with both the battery and solar system. 

With this configuration, DC power from your solar panels charges the battery. The hybrid inverter then converts the DC power into AC electricity for use in your home. DC coupling could be an excellent choice if your solar system is older and your inverter is nearing the end of its expected lifespan. Read up here on how long solar batteries last for.

Finally on the integration, if you’re installing solar panels today with the intention of adding batteries in the future, a ‘storage ready’ option might be the most suitable route. In this case, the inverter is already prepared for the installation of a battery when it becomes financially viable for you. 

What size battery capacity do you need for a solar array?

When sizing a domestic battery storage system for your solar installation, there are several core factors to consider: 

  • The amount of energy you generate – If you have solar panels installed already, how much energy is being generated on a daily basis? Work out your averages across the months and years. 
  • The amount of energy you export to the grid – How much of the energy generated do you export to the national grid? Review your readings and calculate your average export in kWh. This will give you an idea of the available energy that you generally have to send to a battery, rather than to the grid.
  • Your home’s energy consumption – The most crucial factor is knowing your home’s average daily energy consumption. This will provide you with a baseline understanding of your typical electricity usage and, consequently, the amount of energy you need to store.

Striking the right balance between these factors and others, such as your budget, is crucial.

Whilst most people invest in a battery storage system to reduce their reliance on the grid and save money on energy bills, it’s important to have realistic expectations. Unless you have an exceptionally large battery capacity, you’ll still need to buy electricity from the grid throughout the year. Powering your home solely from battery storage is generally not feasible as you’d require a huge battery capacity.

However, when it comes to battery storage, it’s always better to err on the side of a slightly larger capacity. This will provide more flexibility and energy security in the long run. To give you an idea on size:

  • Small batteries – A small solar battery storage system will be sized between 3-10 kWh. A fully charged small solar battery is usually sufficient for powering the bare essentials of a family residence for a full day, such as refrigerators, lighting and electronic devices. However, powering your heating, as well as everything else from this, will be problematic.
  • Medium batteries – A medium battery storage system can hold between 10-15kWh. A fully charged medium solar battery can cover most of the home’s energy needs for a day or two.
  • Large batteries – Large batteries are capable of storing around 15kWh of energy and above. With these batteries, you’ll be more energy independent and may be able to sell electricity back to the grid to generate a side income.

You can read much more on how to calculate battery storage size for solar panels here.

Installing battery storage: a step-by-step process

Adding battery storage to your existing solar panel system is a multi-step process. It involves careful planning and professional installation. 

Here’s a step-by-step guide to help you navigate the process:

  • Research – Brands, installers, and battery systems: Begin by thoroughly researching battery brands, systems and local businesses to familiarise yourself with the available options and their features. It’s always good to have at least a basic understanding.
  • Consult and gather quotes – Contact the companies you like to discuss your specific needs and home setup in more detail. Arrange for them to visit your home and provide quotes and expert advice tailored to your situation.
  • Choose the right kind of battery – Battery system, size/capacity, and integration method: Based on your research and consultations, decide on the type of battery system you want, the appropriate capacity for your needs and the preferred integration method. Generally speaking, you can install 2 to 3 batteries to your solar panel system depending on your energy requirements.
  • Assess the costs – Evaluate the costs associated with both purchasing and installing the chosen battery system. Depending on the size, manufacturer and battery type, costs are usually in the region of £2,500 to £10,000+.
  • Review your energy supplier agreement – Check with your energy supplier to see if you need to update or change your agreement to get the best deal. This is particularly appropriate when selling excess energy back to the grid. Current suppliers tend to offer the best rates here.
  • Decide the best location – Most homes don’t have too many options here but your installer will provide expert insights. A suitable location for your battery storage system needs to be well-ventilated and not exposed to extreme temperatures. Ensure the area is easily accessible for maintenance and has the necessary space for the equipment. Find out how big battery storage systems are.
  • Installation – Arrange for a professional installer to fit the battery system into your mains electricity system and connect it to your existing solar panels.
  • Configure the settings – Work with your installer to set up the system settings and monitoring software. This will allow you to track your energy generation, consumption and storage, as well as optimise your system’s performance.

This last point is important when it comes to maximising efficiencies. By monitoring your system’s performance, you can make sure everything is working as efficiently as possible and that you’re making the biggest cost savings. Regularly reviewing your energy consumption patterns and adapting your battery’s charging and discharging cycles will help you get the most out of your investment and reduce your reliance on the grid.

Wrap up on adding battery storage

Wrap up on adding battery storageAdding battery storage to an existing solar panel system is a viable and beneficial option for many UK homeowners. By carefully assessing your energy needs, researching available battery systems and working with professionals who know what they’re doing, you can successfully integrate a battery solution that fully complements your solar setup. 

About the author 

Ben Hardman

Ben is a professional writer and the creator of sustainable living website
It's here where he helps people to reduce their environmental impact through simple, everyday choices. Away from the laptop, Ben loves spending time in the natural environment with his young family and Murphy the cocker spaniel.

First Class BSc Biology degree (environmental and climate change focus)
Six years of working and writing in the environmental sector, including two years working at an international sustainability consultancy
Written for Ethical Consumer magazine, My Mother Tree, Unsustainable Magazine, Happy Eco News, Emission Index,
Commented in The Independent, The Guardian, GreenMatch. Also featured on Radio 1's environmental special 'Minute of Me'

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