Solar Plus Battery vs Solar-Only for Industrial Units

Once an occupier accepts that solar panels for industrial units pay back, the next question is almost always whether to add a battery. The pitch is appealing: store the midday surplus, use it after the sun drops, sidestep more of the grid bill. But a battery adds a large slice of capex below the panels, and on a smaller unit that cost has to be earned back from a self-consumption gap that may already be small. Whether solar plus battery beats solar-only comes down almost entirely to one thing: your load profile. This guide compares the two routes on the terms that matter to a smaller industrial building, and sets out when the battery pays and when it is money better left in the bank. Every figure below is illustrative and depends on your roof, load, tariff and lease.

The two routes in plain terms

Solar-only. You install rooftop PV sized to your daytime load, consume what you can in real time, and export the surplus for a few pence under the Smart Export Guarantee. It is the simplest, cheapest and lowest-maintenance route, and on a unit whose machinery, lighting and compressed air run through the working day it captures most of the available saving on its own.

Solar plus battery. You add storage that charges from the midday peak and discharges later, into the evening, overnight, or across a weekend when the panels are idle. The battery lifts self-consumption, can shave expensive peak-rate import, and opens the door to grid-service revenue. The trade is a higher upfront cost, a second asset with its own warranty and degradation curve, and a payback that depends on how much of that stored energy you would otherwise have bought at full price.

The two routes head to head

The merits and drawbacks divide across the two routes:

Factor	Solar-only	Solar plus battery
Upfront capex	Lower (panels only)	Higher (panels plus storage)
Typical self-consumption	50-80% on a daytime unit	80-95%+ once stored energy is used
Simple payback	Near 5.5 years on a well-matched unit	Often 8-10 years-plus on a daytime-only site
Resilience / backup	None (system trips on grid loss)	Possible (battery can island critical loads)
Grid services revenue	None	Possible (peak shaving, flexibility markets)
Maintenance and replacement	Inverter mid-life only	Inverter plus battery replacement over 25 years
Best fit	Single daytime shift, high midday match	Multi-shift, evening load, peak charges, resilience needs

The headline trade is simple versus flexible. Solar-only wins on cost and payback wherever daytime load already absorbs the generation. A battery only repays its extra capex when there is a real gap between when you generate and when you use, and the size of that gap is set by your shift pattern, not by the size of your roof.

Why the load profile decides, not the roof

On a big-box logistics shed the binding question is roof area. On a smaller industrial unit the binding question for batteries is the shape of the working day. Solar pays back through self-consumption, and a battery only adds value by moving generation from hours you do not need it into hours you do. So the decision turns on three patterns.

Single daytime shift. A unit running roughly 07:00 to 18:00, Monday to Friday, sees its machinery, lighting and small-power load track the solar curve closely. Self-consumption on solar-only is already high, so there is little surplus left for a battery to capture. Adding storage mostly means storing energy you would have used anyway, and the extra capex struggles to pay back. For the typical single-shift occupier, solar-only is usually the right answer.

Multi-shift or extended hours. A unit working a second or third shift, or running late into the evening, draws power long after generation has fallen away. Here the midday surplus a single-shift site would export can instead be banked and discharged into the evening, displacing expensive grid import rather than earning a few pence on export. This is where a battery starts to earn its keep.

Storage-heavy or low daytime baseload. Units that are largely warehousing with modest process load, or where the real activity is overnight, have a weak match between generation and demand in the first place. A battery can rescue the self-consumption case here, but the underlying solar economics are already marginal, so the right move is often to add daytime load, EV charging being the obvious one, before reaching for storage.

The machinery mix matters too. Sites with heavy, spiky loads such as large compressors, induction heating or welding plant often face high peak-demand or capacity charges, and a battery that shaves those peaks can pay back through avoided charges as much as through stored solar. A unit with a flat, modest load and no peak penalties has far less for a battery to work with.

The other things a battery buys

Two benefits sit outside the pure self-consumption sum and can tip a marginal case.

Resilience. A standard grid-tied solar system shuts down on a power cut, it cannot legally back-feed a dead grid. A battery with the right inverter can island and keep critical loads such as refrigeration, security or a process that must not stop running through an outage. For most general industrial units this is a nice-to-have, but for a unit where downtime is expensive or stock is perishable, it can be the deciding factor on its own.

Grid services. A battery can earn revenue beyond your own bill through grid flexibility, peak-time export, or flexibility markets. These revenues are real but variable and depend on your connection, supplier and current market arrangements, so treat them as upside rather than the basis of the case. Where they apply, they shorten an otherwise long battery payback.

An illustrative worked example

A worked example helps. Take an illustrative composite. A light-industrial SME on a 45,000 square foot leased unit installs around 250 kW across roughly 460 panels, generating in the region of 230,000 kWh a year, at an installed cost between £175,000 and £225,000 on the usual £700 to £900 per kW.

On a single daytime shift, most of that generation is consumed on site as it is produced. Self-consumption is already high, so the surplus a battery could capture is small. Adding storage here lifts self-consumption only a few points while adding a large slice of capex, and the battery payback runs well beyond the panels’ own sub-six-year figure. Solar-only is the stronger route.

Change one thing, give the same unit a second shift running into the evening, and the picture flips. Now a chunk of the midday peak that would otherwise export at a few pence can be banked and discharged into the evening shift, displacing grid electricity bought at full retail plus network charges. The battery is displacing expensive import rather than cheap export, so the extra capex has real saving to work against and the combined system makes sense. These figures are illustrative only and depend entirely on the actual roof, load, tariff, lease and tax position, which is why we start every project from your own half-hourly meter data.

How tax and funding sit across both

Both routes draw on the same levers. Solar PV and storage both qualify as plant and machinery, so the 100% Annual Investment Allowance lets most limited companies write off the qualifying cost against year-one profit up to the £1m cap, worth up to around a quarter of the spend back as tax saved. A battery’s higher capex means a larger allowance but also more cost to recover, so the tax shield helps without changing the verdict. The TNUoS and BSUoS network charges that have risen 40 to 80% since 2022 are what make stored, self-consumed energy valuable in the first place. Funding choice, cash, asset finance or a PPA, applies to both routes alike and is set mostly by tenure rather than by whether a battery is included.

How to choose

The decision tree is short. If your unit runs a single daytime shift with load that tracks the sun, go solar-only, it captures the saving without the extra capex and pays back fastest. If you run a second or evening shift, carry expensive peak or capacity charges, or need backup for critical loads, model a battery properly, because there is a real gap for it to fill. If your daytime load is genuinely low, fix the self-consumption first, often by adding EV charging, before reaching for storage.

The honest answer is specific to your shift pattern, machinery mix and tariff, so model both against your real load rather than your roof size. If you are still weighing whether solar makes sense at all, start with is solar worth it for industrial units. Then review the cost guide for the underlying numbers, the funding routes for the schemes that apply, and the savings calculator for a quick indicative figure. When you are ready, request a free feasibility and we will model solar-only against solar plus battery on your own half-hourly data and return a fixed-price proposal for whichever pays.