Solar battery: costs and savings

Solar batteries allow homeowners to store excess electricity generated by their solar panels for later use, boosting energy self-sufficiency and potentially reducing electricity bills. This guide explains how solar batteries work, their costs, and whether they are a worthwhile investment for your home.

What is a solar battery and how does it work?

A solar battery is a large rechargeable battery that stores surplus electricity from your solar panels. This allows you to use it when the sun is not shining or when your demand is highest, leading to less reliance on the grid and more control over your home's energy.

Storing your solar energy

Solar panels generate direct current (DC) electricity from sunlight. This electricity first powers your home. Any excess DC electricity is then sent to a solar battery for storage. When your home needs power and your solar panels are not generating enough - for example, at night or on cloudy days - the stored energy is released from the battery.

Components of a solar battery system

A typical solar battery system includes the solar panels, an inverter, the battery bank, and control electronics. The inverter converts the DC electricity from your panels into alternating current (AC) electricity, which most household appliances use. For battery storage, the inverter manages the flow of power, converting AC back to DC for storage in the battery and then back to AC when the battery discharges to power your home.

How batteries integrate with your home

Solar batteries act as a buffer between your solar panels and the National Grid. Your home uses solar power first, then draws from the battery. Only when both solar generation and battery storage are insufficient does your home import electricity from the grid. This integration helps you maximise your self-consumption of solar energy.

Benefits of solar battery storage for UK homes

Installing a solar battery offers several advantages for UK homeowners, from financial savings to increased energy independence.

Maximising self-consumption and reducing bills

Solar panels often generate more electricity during the day than a home can immediately use. Without a battery, this surplus is typically exported to the grid, often at a low rate. A solar battery allows you to store this excess energy and use it later, significantly increasing the amount of self-generated electricity you consume. This reduces the amount of electricity you need to buy from the grid, leading to lower energy bills.

The average UK home uses around 2,500 kWh of electricity per year1. With electricity unit rates for a typical Direct Debit household on the Ofgem Price Cap default tariff at 26.11p per kWh (inclusive of 5% VAT) from 1 July to 30 September 2026, every unit you generate and use yourself avoids this cost.

Achieving greater energy independence

By storing your own solar energy, you become less reliant on the National Grid and its fluctuating electricity prices. This gives you more control over your energy supply and can provide a sense of security against future price rises. You can also track your usage and generation more effectively with a smart meter installation.

Protecting against power outages

Some solar battery systems can provide backup power to essential appliances during a power cut. This feature, known as 'blackout protection' or 'EPS' (Emergency Power Supply), ensures that critical loads in your home remain operational even when the grid goes down.

Types of solar batteries and key considerations

Choosing the right solar battery involves understanding different technologies and matching them to your home's specific needs.

Battery chemistry: lithium-ion and beyond

Lithium-ion batteries are the most common and popular choice for residential solar storage in the UK. They offer high energy density, a long lifespan, and require little maintenance. Within lithium-ion, Lithium Iron Phosphate (LiFePO4) is a notable type known for its safety, long cycle life, and thermal stability. Other chemistries like lead-acid batteries are cheaper but have shorter lifespans and higher maintenance needs, while flow batteries are generally too complex and expensive for typical residential use.

Capacity and power ratings explained

Battery capacity, measured in kilowatt-hours (kWh), indicates how much energy the battery can store. Power rating, measured in kilowatts (kW), shows how much electricity the battery can deliver at any given moment. For residential use, wired home solar battery storage systems typically range from 3 kWh to 20 kWh in capacity.

When sizing a battery, it is crucial to match its capacity to your evening and overnight electricity usage, rather than solely to the size of your solar array. Most UK homes need a solar battery between 5 kWh and 16 kWh. An average UK household uses around 6.8 kWh a day, suggesting a 7-10 kWh battery as a sensible starting point for many.

Inverter compatibility and system design

The inverter is a critical component that converts DC electricity from your solar panels into AC for your home and manages the flow to and from the battery. When adding a battery to an existing solar panel system, your installer will need to check if your current inverter is battery-compatible. System design also considers whether the battery will be AC-coupled (connected after the solar inverter) or DC-coupled (connected before or directly to the solar inverter), each having implications for efficiency and cost.

Costs, savings, and return on investment

Investing in a solar battery involves an upfront cost, but it can lead to significant long-term savings and a quicker return on your investment.

Average solar battery costs in the UK

The average solar storage battery for a UK home costs around £5,000, with prices ranging from less than £2,000 to over £11,000. Installed costs for a complete system, including the battery, can range from £3,000 to £10,500 depending on capacity, brand, and installation complexity. A 10 kWh solar battery typically costs around £4,000-£6,000 installed. Installing solar panels and a battery at the same time can reduce the overall cost.

Calculating your potential savings

Your potential savings depend on how much of your self-generated electricity you use, your electricity tariff, and how you manage your battery. By storing solar power for use during peak times, you avoid buying expensive grid electricity. Some homeowners can save between £300 and £1,000 per year, particularly with smart tariffs designed for solar and battery users. These savings contribute to your efforts to reduce energy bills.

Understanding payback periods

The payback period is the time it takes for the savings on your electricity bills to cover the upfront cost of the solar battery system. Payback periods for solar and battery installations in the UK typically range from 7 to 15 years. Factors like your household electricity use, the size and orientation of your roof, and the specific tariff you are on all influence this. After the payback period, the electricity generated and stored effectively becomes free, leading to years of pure profit.

Choosing the right solar battery system

Selecting the ideal solar battery system requires careful consideration of your energy habits and future needs.

Assessing your energy needs

Start by understanding your household's daily electricity consumption. Review your energy bills or use a smart meter app to track your average daily kWh usage. Pay close attention to when you use the most electricity, especially during the evening and overnight when solar panels are not generating. This will help determine the appropriate battery capacity.

Comparing brands and warranties

Many brands offer solar battery systems in the UK, including Tesla, Fox ESS, Pylontech, and Sigenergy. When comparing options, look at the battery's usable capacity, cycle life (how many times it can be charged and discharged), and the warranty period. Most modern lithium-ion batteries are warranted for at least 10 years and are expected to operate at 70% capacity or more after this time.

Wired home batteries vs plug-in options

Wired home battery storage systems are professionally installed and integrated into your home's electrical system. These are distinct from plug-in batteries, which are smaller, portable units that plug into a standard wall socket.

SI 2026/848 legalises compliant standalone plug-in solar (up to 800W AC export) but does not apply to plug-in batteries or hybrid solar-battery kits. This means plug-in batteries are not covered by the recent legislation change for plug-in solar.

Wired systems offer greater capacity and seamless integration, while plug-in options are generally for smaller-scale, temporary use and do not fall under the same regulatory framework as wired home systems.

Installation and regulatory requirements

Installing a wired home solar battery system involves professional expertise and adherence to specific regulations.

Professional installation process

Wired home battery storage systems require professional installation. A certified installer will assess your home's energy use, existing electrical setup, and available space to recommend the right system. The installation process typically involves mounting the battery unit, connecting it to an inverter, and integrating it into your home's electrical system. Most installations take one to two days.

DNO notification and safety standards

Professional installation includes notifying your Distribution Network Operator (DNO). This notification is a regulatory requirement under G98 and must be completed within 28 days of installation by either the homeowner or their supplier. This ensures the local electricity network is aware of your new energy generation and storage system. All installations must comply with relevant safety standards to ensure the safe operation of the battery system.

Smart Export Guarantee (SEG) eligibility

The Smart Export Guarantee (SEG) provides payments for electricity exported to the grid from eligible, MCS-certified installations. Self-installed plug-in solar kits do not have MCS certification and therefore do not qualify for SEG payments. While SEG does not apply to these smaller systems, some suppliers may offer their own export tariffs for unused generation.