30kW Solar System UK: The Complete 2026 Guide for Small and Growing Businesses

For many small and growing businesses, that’s not always an easy call. A full commercial system can feel too large, too complex, or simply more than you need. At the same time, doing nothing means continuing to absorb rising energy costs with no control over them.

That’s where a 30kW system sits: large enough to make a meaningful reduction to your electricity bill, but simple enough to install without the delays and complexity that come with larger systems. By the end of this guide, you’ll understand whether a 30kW system fits your business, what it’s likely to save you in real terms, and what factors will determine whether it performs well or falls short. For a broader overview of commercial solar costs and system sizes, see our dedicated guide.

Why 30kW Is Often the First Size Businesses Seriously Consider

Most businesses don’t start by choosing a system size. They start by asking whether solar is worth doing at all. A 30kW system tends to be where the answer becomes ‘yes’ for two reasons: it’s large enough to make a meaningful impact on costs, but small enough to stay simple to deliver.

On the financial side, a system generating around 25,500 kWh per year can remove a noticeable portion of an electricity bill. For a business spending £8,000–£15,000 annually, that translates into savings big enough to justify the investment rather than just offsetting a small fraction of costs. On the practical side, 30kW sits just below the point where projects become more complex. Larger systems require G99 grid approval before installation, which introduces delays and uncertainty. At 30kW, that step is typically avoided, so the project can move straight from design to installation without waiting.

• Smaller systems are easier to install, but don’t always generate enough to justify the effort
• Larger systems generate more, but come with longer timelines and more complexity
• 30kW sits in the middle: savings are meaningful and the process is still straightforward

Is a 30kW System the Right Fit for Your Business?

This is the most important question in the entire decision. A 30kW system is not defined by the type of building you have, it is defined by how your business uses electricity throughout the day. Solar generates electricity during daylight hours. The more of that electricity you use at the time it is generated, the more value the system creates.

The simplest way to assess fit: if your business uses most of its electricity between 8am and 5pm, a 30kW system is likely to perform well. If a significant portion of your energy use happens after those hours, the system still works, but a battery may be needed to capture more of that value. There is also a natural sizing boundary: a 30kW system generating around 25,500 kWh per year typically suits businesses spending up to roughly £15,000 per year on electricity. Beyond that, the system starts to feel small relative to demand, and larger systems become more appropriate. Our commercial solar regulations guide covers additional planning considerations for different property types.

What a 30kW System Actually Does in Real Terms

A 30kW system generates around 25,500 kWh per year (30 kWp × 850 kWh/kWp, the MCS standard irradiance figure), but that number only matters when you understand how it reduces your bill. It doesn’t power your entire business. It targets a specific part of your energy use: your daytime consumption. In most businesses, there’s a consistent level of electricity use during the day — lighting, refrigeration, IT systems, equipment running in the background, anything operating between opening and closing hours. That’s what solar replaces first.

The financial difference comes down to this: electricity you use from solar saves ~27p/kWh (current Ofgem Q2 2026 commercial rate), while electricity you export earns much less. A 30kW system is not designed to eliminate your electricity bill — it’s designed to consistently remove a large portion of it, typically 30–60%, depending on how your business operates.

Cost and What You’re Really Paying For

A 30kW solar system typically costs between £30,000 and £36,000 (ex-VAT), with most projects landing around £32,000. On its own, that number doesn’t mean much — the important part is how that cost breaks down per unit of generation and over time. At this size, you’re effectively paying for a system that will generate around 25,500 kWh every year for 25+ years, locking in a long-term supply of electricity at a fixed price rather than continuing to buy at fluctuating grid rates. For a full comparison across commercial system sizes, see our commercial solar cost guide.

What actually drives the cost

The total price is shaped less by individual components and more by three practical factors: roof complexity (simple, unobstructed roofs are quicker and cheaper to install), electrical integration (how easily the system connects into your existing supply), and access and installation conditions (height, layout and ease of installation). Panels and inverters are relatively standardised at this level — the variation in cost usually comes from the site, not the equipment.

What the Savings Actually Look Like

The system generates the same amount of energy regardless of the business. What changes is how much of that energy is used on site. For a business that operates during the day, around 70% of that energy is typically used directly. For businesses with more evening usage, that figure drops closer to 50%. That difference is what drives the financial outcome. All figures below use the current commercial electricity rate of 27p/kWh and a conservative SEG export rate of 7p/kWh.

Daytime-heavy business (e.g. clinic, school, retail)

Mixed-hours business (e.g. office, warehouse, care home)

The key takeaway: performance is not just about the system, it is about how well the system fits the way your business uses electricity.

The Tax Case in Plain Terms

At 30kW, tax relief is not a minor benefit — it is a core part of the financial case. The Annual Investment Allowance (AIA) allows your business to deduct the full cost of the solar system from taxable profits in the year it is installed, meaning the saving is realised immediately rather than spread over time. For a full breakdown of tax relief mechanisms and business grants, see our commercial solar grants guide.

Without tax relief, a system saving ~£5,000–£6,000 per year is a solid investment. With AIA, you’re effectively investing closer to £24,000–£26,000 (at 25% rate), which significantly improves the return and pushes payback into the 4–5 year range for daytime-heavy businesses.

Battery Storage: When It Changes the Outcome

At 30kW, a battery is not about improving generation — it’s about recovering energy you would otherwise lose. The system already produces around 25,500 kWh per year. The question is how much of that you actually use. If most of it is already used during the day, a battery has limited impact. If a large portion is being exported, the impact becomes much more meaningful.

A typical 30kWh battery adds £12,000–£20,000 to the project. For daytime businesses, the additional savings are relatively small, which means payback on the battery itself is slow. For evening-heavy businesses, the situation is different — a battery allows you to use energy that would otherwise be exported at a low rate, significantly improving overall system value. The simplest decision rule: if most of your electricity is used between 8am and 5pm, solar-only is usually the stronger financial choice. If your electricity use remains high in the evening, a battery becomes worth serious consideration. Many businesses install solar first, monitor how much they export, and then decide whether adding storage will materially improve the outcome.

The Sizing Decision Most Businesses Get Wrong

At 30kW, most businesses don’t accidentally overspend — they accidentally undersize. Not because they’ve done the maths wrong, but because they’ve based the decision on what their electricity use looks like today, rather than what it’s likely to look like once the system is in place. Electricity demand in most businesses doesn’t stay flat. It tends to increase in small, almost unnoticeable ways:

• An extra fridge, unit or piece of equipment
• Longer opening hours or more staff
• EV charging, even at a small scale
• Higher throughput or additional services

If your current usage already sits close to the system’s annual output (~25,500 kWh), then a 30kW system will feel well-matched today but potentially tight in a few years. Adding extra capacity later is rarely a simple extension — it can involve new design work, additional installation costs, potential changes to the inverter or layout, and in some cases moving into G99 approval territory. That is why many businesses who install 30kW systems don’t regret going solar, they regret not going slightly larger when they had the chance. The goal is not to install the biggest system possible — it is to install a system that still feels correctly sized once your business has moved forward.

What the Installation Actually Involves

At 30kW, the installation itself is not complicated. What matters is how the process is managed from the start. Because the system falls under G98 Type B, the project moves forward without waiting for external grid pre-approval — the timeline is driven by design quality and scheduling, not the grid. The full process typically takes around 4–8 weeks, with most of that time spent on planning and scheduling rather than on-site work.

Step 1: Site survey — understanding your building and usage

This is where the project is set up properly. The installer assesses the roof structure, usable space, electrical setup and how your business actually uses electricity during the day. The important part here is not just the roof — it’s the usage. A system sized incorrectly at this stage will underperform regardless of how well it is installed.

Step 2: System design — where performance is decided

This is the most important stage of the project, even though it’s not visible on site. The system is designed around how much energy you can realistically use, how panels are laid out across the roof, and how the inverter is configured. Good design is what ensures the system produces usable energy, not just theoretical output.

Step 3: Scheduling and preparation

Once the design is agreed, equipment is ordered and installation is scheduled. Because there is no G99 approval delay at this size, this stage moves quickly and predictably. Access to the site is planned, and the project is prepared so installation can happen without interruption.

Step 4: Installation

In reality, this is the shortest and least disruptive part of the process. Panels, mounting systems and inverters are installed over a few days, with most of the work taking place on the roof. For most businesses, operations continue as normal, with minimal need for access inside the building and no interruption to power supply.

Step 5: Commissioning

Once installed, the system is tested and connected. Electrical checks are completed, performance is verified, and monitoring is set up so you can track generation and savings. From this point, the system is live and immediately starts reducing your reliance on grid electricity.

Step 6: DNO notification (G98)

The grid operator is notified after installation. This is handled by the installer and does not delay the system going live. It is a compliance step, not a blocking one — which is what makes the process at 30kW much simpler than for larger systems requiring G99 pre-approval.

Conclusion

A 30kW solar system is often the point where commercial solar becomes both practical and worthwhile for small businesses. It delivers a meaningful reduction in electricity costs, avoids the delays associated with larger systems, and provides a clear financial return without unnecessary complexity.

The key is not just installing solar, but installing a system that fits how your business actually uses energy — both now and as it grows. Undersizing today because current demand looks modest is one of the most common mistakes at this scale, and one of the hardest to correct later without additional cost. For a full overview of what businesses need to consider before going ahead, see our guide to the 10 things commercial solar panels in the UK require.

Frequently Asked Questions