Solar Battery Storage Systems: How They Work and Is One Right for Your Business?

A solar battery storage system stores surplus electricity from a solar PV array so a business can use it later instead of exporting it to the grid. On UK commercial sites, the battery shifts solar generation into evenings, peak-rate periods and cloudy spells, reducing grid imports and increasing the value of every kilowatt-hour (kWh) the panels produce.

This guide is written for operations directors, finance leads, facilities managers and sustainability teams considering battery storage for solar PV. It explains how commercial systems work, what they cost, how they are sized, which tax reliefs and grid rules apply in 2026, and where a battery does and does not make financial sense.

Key Takeaways

• A solar battery storage system stores surplus solar PV generation for later use on site, increasing self-consumption and reducing grid imports.
• The strongest business cases stack value streams: solar self-consumption, red band and capacity charge savings, winter grid arbitrage, avoided curtailment and, where suitable, flexibility revenue.
• UK non-domestic electricity averaged 24.14p per kWh in Q1 2026 (DESNZ), well above typical export rates, which is what makes storing rather than exporting solar valuable.
• Backup power is not automatic. Grid-tied systems shut down in an outage unless designed with islanding and changeover switchgear.
• LFP is the standard chemistry for new commercial storage; compare quotes on usable kWh, warranted cycles and retained capacity.
• Tax relief and rates relief improve payback: the AIA gives 100% first-year relief up to £1m, and in England on-site storage is exempt from business rates until 31 March 2035.
• Size from half-hourly data, not annual totals, and involve the DNO, insurer and fire safety requirements early.

What Is a Solar Battery Storage System?

A solar battery storage system is a rechargeable battery, plus power electronics and controls, connected to a solar PV installation. It charges when the panels generate more electricity than the site is using and discharges when demand exceeds generation. For businesses, this turns rooftop solar PV from a daytime-only supply into a controllable energy asset.

Without storage, surplus solar is either exported to the grid (often for a lower price than the site pays to import) or curtailed if the grid connection cannot accept it. A battery captures that surplus for later use on site. Commercial systems typically range from tens of kWh on smaller premises to several megawatt-hours (MWh) on industrial sites.

Key battery storage terms explained

• kWh (energy capacity): How much energy the battery holds. Determines how long it can supply a load.
• kW (power rating): How fast the battery can charge or discharge. Determines how large a load it can cover at once.
• Usable capacity: The energy you can actually draw, after the manufacturer’s depth-of-discharge limits. Always compare quotes on usable kWh.
• Round-trip efficiency: The share of energy put into the battery that comes back out. The remainder is lost as heat in conversion.
• Cycle: One full charge and discharge. Warranties usually specify a cycle limit and a minimum retained capacity.
• Behind-the-meter: A battery installed on the customer’s side of the meter, primarily serving the site’s own demand.

How Do Solar Battery Storage Systems Work with Solar PV?

Solar PV panels generate DC electricity. An inverter converts it to AC to power the building. When generation exceeds demand, the energy management system routes the surplus into the battery instead of exporting it. When demand exceeds generation, typically in the late afternoon, evening or on overcast days, the battery discharges to supply the site before any electricity is bought from the grid. A typical daily sequence on a commercial site looks like this:

1. Morning: solar output rises and first meets the site’s base load.
2. Midday: generation exceeds demand. Surplus charges the battery.
3. Battery full: any remaining surplus is exported (within the site’s agreed export limit) or curtailed.
4. Late afternoon and evening: solar output falls while demand stays high. The battery discharges, often targeting the most expensive tariff periods.
5. Overnight (optional): the battery can charge from the grid at a cheaper rate, ready for the next day’s peak.

For a primer on how the panels themselves generate electricity, see how solar panels work.

What is the difference between AC-coupled and DC-coupled battery storage?

AC-coupled batteries connect on the AC side of the site’s electrical system with their own bidirectional inverter, so they can be added to an existing solar PV installation without changing it. DC-coupled batteries share a hybrid inverter with the solar array and store DC energy directly, which avoids one conversion step but is usually specified when solar and storage are designed together.

For most existing commercial rooftops, AC coupling is the practical retrofit route. For new builds or large new arrays, the choice depends on system size, inverter availability and where the battery can be sited.

Can a solar battery also charge from the grid?

Yes. Most commercial batteries can charge from the grid as well as from solar PV. This matters in the UK because solar surplus is heavily seasonal: a battery may fill from solar most days in summer but rarely in midwinter. Charging from the grid during cheaper periods and discharging during expensive ones (tariff arbitrage) keeps the battery earning year-round.

Benefits of Solar and Battery Storage for Businesses?

Solar and battery storage lets a business use more of its own generation, avoid the most expensive grid electricity, fit more solar onto a constrained grid connection and, with the right design, keep critical loads running during outages. The size of each benefit depends on the site’s load profile, tariff structure and grid connection, so the business case should be modelled site by site.

1. Using more of your own solar generation

A battery increases solar self-consumption by storing midday surplus for use later the same day. Exported electricity usually earns less than the site pays for imported electricity. Every kWh stored and used on site instead of exported captures that price difference, minus round-trip losses.

According to DESNZ’s Quarterly Energy Prices (June 2026), the average UK non-domestic electricity price including Climate Change Levy was 24.14p per kWh in the first quarter of 2026. That was a 6.2% fall on a year earlier, but DESNZ data also shows non-domestic prices remain on a long-term upward trend compared with pre-2021 levels. Export payments under the Smart Export Guarantee (SEG) are set by individual suppliers and are typically well below import prices.

The wider the gap between your import rate and your export rate, the more a battery is worth for self-consumption alone.

2. Reducing peak-time and capacity charges

Batteries can cut the most expensive parts of a commercial electricity bill, not only the unit rate.

Many half-hourly metered business tariffs include Distribution Use of System (DUoS) charges that are highest in a “red band”, typically a few hours on weekday late afternoons and early evenings, with exact times set by each Distribution Network Operator (DNO) region. Sites also pay for their agreed maximum import capacity. A battery discharging through red band periods reduces the most expensive imports; one that shaves short demand spikes can help a site stay within, or avoid increasing, its agreed capacity.

For sites with a sharp late-afternoon peak, such as manufacturing, cold storage and retail, peak shaving can be worth more than solar shifting.

3. Fitting more solar onto a constrained grid connection

A battery can allow a business to install a larger solar array than its grid connection could otherwise accept.

Where the local network cannot take full export, the DNO may approve a connection with an export limitation scheme compliant with Engineering Recommendation (EREC) G100, published by the Energy Networks Association. National Grid Electricity Distribution states that once commissioned, these limit settings cannot be altered by the customer and may only be changed with the DNO’s written agreement. A battery absorbs generation that would otherwise be curtailed above the export cap.

4. Protecting critical operations during outages

A solar battery only provides backup power if it is specifically designed and installed to do so.

Grid-connected solar and battery systems must disconnect automatically during a grid outage (loss-of-mains protection), so that they do not energise the network while engineers are working on it. To keep running, a system needs islanding capability, changeover switchgear and a defined set of backed-up circuits. The battery’s kW rating must cover those loads and its kWh capacity must cover the required duration.

5. Supporting carbon reduction and reporting

Storing and using on-site solar reduces grid imports and therefore Scope 2 emissions.

Businesses reporting under Streamlined Energy and Carbon Reporting (SECR), or assessed under the Energy Savings Opportunity Scheme (ESOS), must disclose or audit their energy use. Solar with storage gives a measurable reduction to report. Neither SECR nor ESOS provides funding; they are compliance frameworks that often prompt investment.

6. Earning revenue from grid flexibility

Some commercial batteries can earn additional income by responding to signals from the grid operator or network.

The National Energy System Operator (NESO), which replaced National Grid ESO in October 2024, runs flexibility services that smaller assets can access through aggregators. See the incentives section below for details.

Disadvantages of Solar Battery Storage

The main disadvantages of solar battery storage are the upfront cost, gradual capacity loss over time, energy lost in each charge and discharge cycle, and the space, safety and grid approval requirements of commercial systems. UK solar surplus is also seasonal, so a battery charged only from solar will sit partly unused in winter unless it also charges from the grid.

• Capital cost: storage adds significantly to a solar project budget, and the payback is usually longer than for solar PV alone.
• Degradation: usable capacity declines with cycling and age. Warranties typically guarantee a minimum retained capacity over a set period or number of cycles.
• Round-trip losses: some energy is lost as heat in every cycle, so a battery never returns 100% of what it stores.
• Seasonality: in winter, UK solar output is often below site demand, leaving little surplus to store.
• Space and siting: larger systems need a dedicated room or external enclosure with access, ventilation and separation distances.
• Approvals: the DNO must be notified or approve the connection, and some installations need planning permission.
• Backup is not automatic: as explained above, outage protection requires extra design and cost.

None of these rules storage out, but they explain why the strongest business cases combine several value streams rather than relying on one.

Which Battery Technology Is Best for Commercial Solar Energy Storage?

Lithium iron phosphate (LFP) is the default chemistry for new commercial solar energy storage. The US National Renewable Energy Laboratory (NREL) notes in its Annual Technology Baseline that LFP became the primary chemistry for stationary storage from 2021, reflecting its thermal stability, long cycle life and lower cost compared with nickel-based alternatives.

For most UK businesses, the practical question is not which chemistry, but which LFP system: compare usable capacity, warranted cycles, retained capacity at end of warranty, round-trip efficiency and the manufacturer’s UK support.

How Much Does Solar PV Battery Storage Cost for a Business?

Commercial solar PV battery storage in the UK typically costs from around £25,000 for a small system to £200,000 or more for installations above 500 kWh. Cost per kWh falls as systems get larger, because fixed costs such as design, grid applications, switchgear and commissioning are spread over more capacity. The figures below are indicative, exclude VAT and assume standard site conditions.

Indicative EvoEnergy ranges. Payback varies with tariff, load profile, value streams and tax position. A site-specific quote requires a survey and half-hourly data.

What affects the cost?

• Usable capacity (kWh) and power rating (kW): a battery sized to cover a short, sharp peak needs more kW; one sized to cover a long evening load needs more kWh.
• Coupling approach: retrofitting an AC-coupled battery to an existing array differs in cost from a DC-coupled system designed alongside new solar.
• Location and enclosure: indoor plant room, external cabinet or containerised system.
• Electrical works: switchboard capacity, cabling distances and any HV/LV infrastructure upgrades.
• Backup capability: islanding and changeover switchgear add cost.
• Fire safety measures: detection, suppression, separation and any insurer requirements.
• Controls: the sophistication of the energy management system and any integration with EV charging or smart energy management.

VAT is charged at the standard 20% rate on commercial battery installations (the zero rate for energy-saving materials applies to residential property). VAT-registered businesses can normally recover it.

What Size Battery Storage for Solar PV Does Your Business Need?

The right size of battery storage for solar PV is the capacity that captures most of your regular solar surplus and covers your most expensive demand periods, without paying for kWh that will rarely be used. It is calculated from half-hourly consumption data matched against modelled solar generation, not from annual kWh totals.

A robust sizing process follows these steps:

1. Collect at least 12 months of half-hourly meter data to capture seasonal and weekday patterns.
2. Model solar generation for the actual array (orientation, tilt, shading). The Solar Output Calculator gives a first estimate.
3. Identify daily surplus (generation minus demand) across the year, not just in summer.
4. Map peak-cost periods, including red band DUoS times and any capacity constraints.
5. Size kW for the peak and kWh for the duration, then test several sizes against the tariff to find the point where extra capacity stops adding value.
6. Allow for future load such as EV charging, heat pumps or new production lines.

Common sizing mistakes:

• Sizing to the sunniest summer day, leaving capacity idle for much of the year.
• Comparing quotes on nominal rather than usable kWh.
• Ignoring the kW rating, so the battery cannot cover a short, high peak.
• Forgetting degradation, so the system is undersized in later years.

What UK Tax Reliefs and Incentives Apply to Battery Storage?

There is no dedicated UK government grant for commercial solar battery storage, but tax reliefs, a business rates exemption and flexibility markets improve the business case. For most projects the Annual Investment Allowance provides 100% tax relief in the first year on qualifying spend up to £1 million, and in England eligible on-site storage is exempt from business rates until 31 March 2035.

Can a battery earn money from grid flexibility services?

Yes, some commercial batteries can, usually through an aggregator. NESO explains that smaller asset owners can join its services via aggregators, which combine many assets into one portfolio and handle registration and compliance, while larger organisations may register directly. On 25 March 2026, Ofgem approved an evolved design for NESO’s Demand Flexibility Service, which for the first time rewards businesses for increasing electricity use when there is surplus supply, as well as for shifting demand out of peak periods. DNOs also procure local flexibility services in some areas.

Flexibility revenue varies from year to year and depends on availability windows, so treat it as upside rather than the core of the investment case. Using a battery for flexibility events must also be balanced against the site’s own peak-shaving and backup needs.

How can a business finance solar and battery storage?

Businesses can fund solar and battery storage through outright purchase, a power purchase agreement, lease-to-own or a green loan. The right route depends on capital availability, tax position and appetite for ownership.

• CAPEX: own the system outright and claim the capital allowances.
• Power Purchase Agreement (PPA): no upfront capital; pay for the energy used.
• Lease to own: spread the cost and take ownership at the end of the term.
• Green loan: borrow specifically for sustainability investments.

How Do You Maintain a Commercial Solar Battery?

Commercial solar batteries need less maintenance than most building plant, but they are not maintenance-free. A maintenance plan should include remote performance monitoring, periodic inspection of electrical connections and cooling systems, firmware and control software updates, and testing of fire detection, suppression and backup changeover where installed.

Monitoring data also shows whether the battery is operating to its intended strategy. A battery that is charging at the wrong time or holding charge through the red band is losing money without any visible fault. Warranty terms often require documented maintenance, so keep records.

EvoEnergy’s aftercare and optimisation services cover monitoring, servicing and control-strategy tuning. For wider PV servicing, see our guide to solar panel maintenance, or estimate costs with the Maintenance Calculator.

Is Solar Battery Storage Worth It for Your Business?

Solar battery storage is usually worth it for businesses that export a meaningful share of their solar generation, pay high peak-time or capacity charges, face a grid export limit, or need backup for critical operations. It is harder to justify where the site already uses almost all of its solar output during the day and has a flat, low-cost tariff.

Before investing, ask:

• Do you already have, or plan to install, solar PV to generate on-site renewable energy?
• Are you on a time-of-use or demand-based tariff where peak charges significantly affect your bills?
• Would uninterrupted power protect critical operations, equipment or customer services during grid outages?
• Are you pursuing net zero commitments, ESG targets or other sustainability objectives?

If the answer to most of these is yes, a professional site and load assessment is the next step. For the wider solar investment case, see are commercial solar installations worth it for large UK businesses.

Power Up Your Future with Solar Battery Storage Systems

Investing in solar battery storage systems is more than just a tech upgrade, it’s a strategic move towards smarter energy management, reduced carbon emissions, and stronger business resilience. By storing and using your own clean energy, you gain greater control over costs, protect operations from grid instability, and strengthen your sustainability credentials.

Whether you’re looking to enhance your existing solar PV setup or design a brand-new integrated system, EvoEnergy can provide the expertise, technology, and ongoing support to ensure your investment delivers maximum value. With the right solution in place, your business can enjoy consistent energy savings, improved operational security, and a clear path toward net-zero goals.

Considering solar battery storage for your site? EvoEnergy’s engineers can analyse your half-hourly data, model the value streams and design a system around your load profile and grid connection. Make an enquiry or explore our battery storage technology.

Frequently Asked Questions

Can you add battery storage to an existing commercial solar PV system?

Yes. An AC-coupled battery with its own bidirectional inverter can be added to most existing commercial solar PV systems without replacing the array or its inverters. The retrofit needs a DNO application, switchboard capacity checks and a control system that reads site demand and solar output.

Will a solar battery keep my business running during a power cut?

Only if it is designed for backup. Grid-connected systems must disconnect during an outage for safety, so backup requires islanding capability, changeover switchgear and a defined set of critical circuits. Size the battery’s kW and kWh to those critical loads and the backup duration you need.

How long do commercial solar batteries last?

Commercial LFP batteries are commonly warranted for around 10 years, usually with a guaranteed minimum retained capacity or cycle count. Actual life depends on how often the battery cycles, its depth of discharge and its operating temperature. Check what the warranty guarantees at the end of the term, not just its length.

What is the difference between kW and kWh in battery storage?

kWh measures how much energy a battery stores; kW measures how quickly it can deliver that energy. A 200 kWh battery rated at 100 kW can supply 100 kW for about two hours. Peak shaving depends mainly on kW; covering long evening loads depends mainly on kWh.

Do I need DNO permission to install commercial battery storage?

Yes. Batteries are treated as generation for connection purposes. Small type-tested systems up to 16A per phase fall under EREC G98 notification, while most commercial systems need an EREC G99 application and approval before connection. Where export must be capped, a G100 limitation scheme is also required.

Is VAT charged on commercial battery storage?

Yes. Commercial battery installations are charged VAT at the standard 20% rate, as the zero rate for energy-saving materials applies to residential property. VAT-registered businesses can normally reclaim it.

Does battery storage increase business rates?

Not in England until at least March 2035. Eligible on-site renewable generation and storage plant, including battery storage, have been exempt from business rates since 1 April 2022, with the exemption running to 31 March 2035. Rules differ in Scotland, so check locally.

Is a battery worth it if my business uses all its solar during the day?

Often not for self-consumption alone. If there is little surplus to store, the case rests on other value streams such as peak shaving, capacity charge reduction, winter grid arbitrage or backup. A half-hourly data analysis will show whether those justify the cost.

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About the Author

Author

Paul Lukehurst

Principal Design Engineer · Since 2015

Paul Lukehurst is a Principal Design Engineer at EvoEnergy, with over 10 years' experience in the renewable energy sector across engineering and leadership roles. His expertise spans the full project lifecycle — from feasibility and financial modelling through to detailed design, procurement, and delivery oversight — ensuring systems are technically sound, buildable, and maintainable.

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