Solar-Plus-Storage (Self-Consumption): Battery storage for business

Why solar-plus-storage is the highest-return battery storage for businesses that already generate

If your business already has rooftop solar, the cheapest energy you will ever buy is the daytime generation you currently spill to the grid. Most commercial solar sites self-consume only 40 to 60 percent of what they produce, export the surplus at a low Smart Export Guarantee rate, then re-import in the evening and early morning at full retail price. That gap between what you are paid to export and what you pay to import is money left on the table every single day. Adding battery storage closes it. A battery sized to your daytime surplus stores the midday excess and releases it into the evening and overnight load, lifting self-consumption from the typical 40 to 60 percent toward 80 percent and above. For a business carrying a six or seven-figure electricity bill, that shift in self-consumption is one of the most reliable energy savings available in 2026.

This is the strongest fit for battery storage for business where on-site load is daytime-light but evening or early-morning heavy, the classic mismatch on offices, food production, light industrial units and retail that run solar but draw their hardest after the sun has gone. The discipline that makes it work is sizing. A solar-plus-storage battery is not sized to your headline solar capacity, it is sized to the shape of your daytime export surplus, which is why we always begin with at least twelve months of half-hourly meter data and your generation profile rather than a kilowatt-per-pound rule of thumb. Get the surplus profile right and the battery earns its keep every day. Get it wrong and you have either an oversized asset that never fills or an undersized one that still spills solar at noon.

It is worth being honest about where this does not pay. A flat, daytime-heavy load that already self-consumes most of its solar has little surplus to store, and a battery added to that profile will struggle to justify itself. We will tell you that plainly rather than sell you a system your data does not support. Boards have heard inflated battery payback claims before, and the only credible answer is a model built from your own half-hourly readings and your real generation curve, shared in full so your finance team can pull it apart. The value of solar-plus-storage is specific to your site, and it is large precisely where the mismatch between when you generate and when you draw is large. That is the question we answer first, before any kit is specified.

What a typical install looks like and how we size it

A commercial solar-plus-storage battery typically lands in the 50 kW / 100 kWh to 500 kW / 1,000 kWh range, paired with your existing or a new solar array. Because the battery stores rather than generates, the right figures to watch are power (in kW) and usable energy (in kWh), not panels or roof area. A system of this scale displaces enough grid import to save in the region of 10 to 120 tonnes of CO2 a year, depending on how much solar surplus you currently waste and how carbon-intensive your evening grid import is. We never size to fill a target number. We model the daytime export surplus across the seasons, because a summer solar peak that overflows a small battery may underfill the same battery in midwinter, and we set power and duration to capture the realistic surplus rather than the theoretical maximum.

Most behind-the-meter commercial batteries land at 1.5 to 2.5 hours of duration, for example a 250 kW unit with 500 kWh of usable capacity, and solar-plus-storage is no exception. The power rating is set by how fast your evening load draws the stored energy down, and the energy rating is set by how much surplus you have to store. We pull your half-hourly data, overlay your generation curve, and show you the surplus you are currently exporting at the Smart Export Guarantee rate so you can see exactly what the battery recovers. That evidence-led sizing is the difference between a battery that pays back and one that disappoints.

Chemistry matters as much as sizing. We specify lithium-iron-phosphate cells for almost all commercial installs, because they offer longer cycle life, far greater thermal stability and a much lower thermal-runaway risk than the older nickel-manganese-cobalt cells they have largely replaced in new UK commercial systems. Quality lithium-iron-phosphate cells are typically warranted for around 6,000 to 10,000 cycles, or ten years, to roughly 70 percent retained capacity, so we size with end-of-life capacity in mind: the system should still capture your solar surplus late in its life, not just on day one. Where it makes sense, augmentation, adding cells later, keeps the usable capacity on target. The warranted cycle count, throughput and degradation curve are stated in every proposal so there are no surprises about how the asset performs across its life.

Costs, payback and tax relief

A solar-plus-storage project typically runs £60,000 to £600,000 depending on the power and energy you need and any switchgear or grid works, with a simple payback near 7 years in 2026 and faster where your solar surplus is large and your evening import expensive. The single biggest financial lever is tax relief. Qualifying battery plant counts as plant and machinery, so the Annual Investment Allowance covers the first one million pounds of qualifying spend at 100 percent, and because storage is a special-rate asset the 50 percent First-Year Allowance applies to qualifying expenditure above that cap. For a limited company that can mean an effective tax saving of up to around a quarter of the project value in year one. The Smart Export Guarantee still has a role: rather than spilling solar at midday for a low rate, a battery lets you shift export into higher-priced windows on a flexible export tariff, so even your export earns more. Our cost guide works through the numbers from your own bill.

Funding routes in detail

Most of the storage we deliver does not have to be paid for from capital. The plant and machinery capital allowances are the headline route: 100 percent Annual Investment Allowance on the first one million pounds, then a 50 percent First-Year Allowance on the balance, which materially improves the after-tax position and is worth confirming with your accountant for the relevant accounting period. The Smart Export Guarantee turns surplus into income, and storage adds most of its value here by timing exports into peak-price periods rather than dumping at noon. Where a building is residential accommodation or used solely for a relevant charitable purpose, the 0 percent VAT relief on energy-saving materials can apply to standalone retrofit battery storage, a relief that runs to 31 March 2027 before reverting to 5 percent, though it does not apply to general commercial premises. For larger behind-the-meter assets, NESO grid services can add upside, but we treat any frequency-response income as a bonus, never the core case. We model capital, asset finance, lease and shared-savings routes side by side so the funding fits your balance sheet.

Compliance and sector considerations

Where your combined generation and storage export could exceed your distribution network operator limits, a G99 application is required, and a G100 export limitation scheme is often used to keep the site inside its agreed export capacity. The storage element should be installed to MCS or an equivalent commercial standard, with the inverter and battery meeting BS EN 62619 for cell safety and BS EN 62933 for system safety. Fire safety has tightened, and rightly so: we design with lithium-iron-phosphate cells, battery management, thermal monitoring and appropriate separation in line with PAS 63100 principles, and we engage your insurer up front, because insurers are comfortable with correctly specified, standards-compliant systems and wary only of cheap, non-compliant kit. Behind-the-meter enclosures on an existing commercial site are often permitted development or a minor application, subject to siting, size, and any listed-building or conservation-area constraints.

How we approach this kind of project

We start with your half-hourly meter data and your generation profile, not a generic estimate, because the whole case for solar-plus-storage rests on the real shape of your surplus and your evening draw. We size for self-consumption first, recovering the solar you currently export cheaply, and we model demand-charge savings as supporting value rather than the headline. We check the practicalities early: enclosure siting, fire separation, switchgear and any roof or asbestos issues where the battery integrates with existing plant. We submit the G99 application alongside the survey so the network clock starts on day one, because the distribution network operator timeline is almost always the longest item. You receive a fixed-price proposal with the warranted cycle count and degradation curve stated in full, backed by an insurance-backed warranty, and we share the complete model so your finance team can stress-test every assumption.

From contract to commissioning, a behind-the-meter solar-plus-storage project typically takes around four to nine months, with the physical installation a matter of one to six weeks once the kit is on site. The long pole is almost always the network: a G99 study and connection can run anywhere from a few months to well over a year depending on local capacity, which is exactly why we lodge the application at the survey stage rather than after design sign-off. Where export capacity is tight, a G100 limitation scheme lets the project proceed without waiting for full export headroom. Once commissioned, the battery is kept working by a planned operation and maintenance contract, remote monitoring with automated alerts, periodic electrical inspection, firmware updates, thermal-management checks and cell-balancing oversight through the battery management system, with software-led optimisation choosing when to charge and discharge as tariffs and DUoS bands move so the system keeps capturing the maximum value over time.

An illustrative example

As an illustrative composite based on typical UK projects, and not a real named client: a precision-engineering plant on a single-shift-plus profile already ran a 300 kW rooftop solar array but exported much of its midday surplus at a low rate while drawing hard in the late afternoon. We modelled a 250 kW / 500 kWh lithium-iron-phosphate battery integrated with the existing solar. In the model, solar self-consumption lifted from around 52 percent toward 84 percent, the late-afternoon red-band import fell sharply, and the combined saving reflected both recovered solar and reduced demand charges, with the full case built from twelve months of half-hourly data and handed to the finance director to stress-test. Any frequency-response income was treated as unmodelled upside. The figures are illustrative and depend on your generation profile, demand shape and tariff.

If your interest is more about flattening demand peaks than recovering solar, see our pages on peak shaving and load shifting and backup power and resilience. When you are ready, read the cost guide and funding routes, request a free feasibility from your meter data, or browse the battery storage FAQs first.