30kW Solar System UK: The Complete 2026 Guide for Small and Growing Businesses
A 30kW solar system typically costs £30,000–£36,000 (ex-VAT) and suits small and growing businesses that want a meaningful cut to their electricity bill without the scale of a large commercial install. It generates around 25,500 kWh a year — enough to offset a sizeable share of daytime energy use for the right site. The catch most buyers miss is that a system this size still needs G99 grid approval before installation. As a result, the timeline starts well before anyone reaches the roof.
- 1. Why 30kW is often the first size businesses seriously consider
- 2. Is a 30kW system the right fit for your business?
- 3. What a 30kW system actually does in real terms
- 4. Cost and what you’re really paying for
- 5. What the savings actually look like
- 6. The tax case in plain terms
- 7. Battery storage: when it changes the outcome
- 8. The sizing decision most businesses get wrong
- 9. What the installation actually involves
- 10. Conclusion
- 11. FAQs
The Short Version (Read This First)
What small and growing businesses need to know about a 30kW solar system:
- A 30kW system generates around 25,500 kWh per year — enough to cover a meaningful share of energy use for most small commercial sites
- Like other systems above the small-scale threshold, it needs G99 grid approval before installation (typically 6–12 weeks) — the main timeline driver, not the install
- The system works best for businesses using most of their electricity between 8am and 5pm, because daytime usage drives the savings
- The Annual Investment Allowance (AIA) lets the full system cost be deducted from taxable profits in Year 1, which compresses payback
- Battery storage only adds material value where a significant share of generation would otherwise be exported — daytime-heavy businesses typically get stronger returns without it
- The most common mistake is sizing to today’s demand rather than allowing for growth, because adding capacity later is rarely a simple extension
- Solar4Good® designs and installs commercial solar systems across the UK — call 0800 999 1454 or visit solar4good.co.uk for a tailored assessment
For many small and growing businesses, going solar is not 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 is where a 30kW system sits. It is large enough to make a meaningful dent in your electricity bill, but small enough to install without the engineering complexity of much larger arrays. 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. Instead, they start by asking whether solar is worth doing at all. A 30kW system tends to be where the answer becomes ‘yes’. There are two reasons: it is large enough to make a meaningful impact on costs, yet the engineering and roof works stay manageable.
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, a 30kW array keeps the design and installation straightforward compared with very large systems. However, it does sit above the small-scale G98 threshold, so it requires a G99 application to your network operator before installation. That approval typically takes 6–12 weeks, and it is the main thing that sets the timeline — so it is worth starting early.
- 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 greater engineering complexity
- 30kW sits in the middle: the savings are meaningful and the build stays straightforward, once G99 approval is in place
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. Instead, it is defined by how your business uses electricity through the day. Solar generates electricity during daylight hours, so the more of that electricity you use as it is generated, the more value the system creates.
| Business type | Typical usage pattern | How 30kW performs |
|---|---|---|
| Dental practices, clinics | Equipment-heavy, daytime | Strong — most energy used on site |
| Schools and nurseries | Daytime only | Very strong — excellent alignment |
| Retail, dealerships | Open during the day | Strong — consistent demand |
| Warehouses (small–medium) | Daytime operations | Good — steady baseline usage |
| Care homes | 24/7 usage | Good — system offsets constant demand |
| Restaurants, pubs | Evening-heavy | Moderate — more export unless battery added |
| Gyms, leisure | Mixed usage | Moderate — depends on operating hours |
The simplest test of fit
The simplest way to assess fit is this: 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. However, 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.
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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 once you understand how it reduces your bill. It does not power your entire business. Instead, it targets a specific part of your energy use: your daytime consumption. In most businesses, there is a consistent level of electricity use during the day. This includes lighting, refrigeration, IT systems and background equipment running between opening and closing hours. That is what solar replaces first.
| Situation | What happens |
|---|---|
| Strong daytime usage | Most solar energy is used on site → higher savings |
| Mixed usage | Some energy used, some exported → moderate savings |
| Evening-heavy usage | More energy exported → lower savings without a battery |
The financial difference comes down to this. Electricity you use from solar saves around 27p/kWh, the current Ofgem Q2 2026 commercial rate. Electricity you export, by contrast, earns much less. A 30kW system is not designed to eliminate your electricity bill. Instead, it consistently removes a large portion of it, typically 30–60%, depending on how your business operates.
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💡 A note on the figures
The cost ranges here are general 2026 UK guide prices, and the savings and payback figures are illustrative estimates for typical sites — not a quote or a guarantee. Your actual return depends on your tariff, usage profile, roof and site conditions. A site-specific assessment gives accurate numbers.
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 the cost breaks down per unit of generation and over time. At this size, you are effectively paying for a system that will generate around 25,500 kWh every year for 25+ years. That locks in a long-term supply of electricity at a fixed price, rather than buying at fluctuating grid rates.
| Metric | Value |
|---|---|
| System size | 30 kW |
| Typical cost range (ex-VAT) | £30,000–£36,000 |
| Cost per kW | £1,000–£1,200 |
| Annual generation (UK average, 850 kWh/kWp) | ~25,500 kWh |
What actually drives the cost
The total price is shaped less by individual components and more by three practical factors. These are roof complexity (simple, unobstructed roofs install faster and cheaper), electrical integration (how easily the system connects into your supply), and access conditions such as height and layout. Panels and inverters are relatively standardised at this level, so the variation in cost usually comes from the site, not the equipment.
⚠️ Honest note: VAT on commercial solar
Commercial solar installations are subject to 20% VAT. Most VAT-registered businesses (turnover above £90,000) can reclaim this as input tax on their next quarterly VAT return, so it does not affect long-term cost. For businesses below the VAT threshold, the 20% VAT is a real additional cost to factor in. All figures in this guide are ex-VAT unless stated otherwise. Worked example at £32,000 (ex-VAT): VAT paid upfront is £6,400, the VAT reclaimed is £6,400, so the effective cost to a VAT-registered business is £32,000.
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, and they are estimates rather than a guarantee.
Daytime-heavy business (e.g. clinic, school, retail)
| Metric | Solar only | Solar + battery |
|---|---|---|
| Annual generation | ~25,500 kWh | ~25,500 kWh |
| Self-consumption | 70% | 85% |
| On-site value (27p/kWh) | ~£4,820 | ~£5,852 |
| Export value (7p/kWh) | ~£536 | ~£268 |
| Total annual benefit | ~£5,356 | ~£6,120 |
| Payback (after AIA at 25%) | ~4–5 years | ~6–7 years |
Mixed-hours business (e.g. office, warehouse, care home)
| Metric | Solar only | Solar + battery |
|---|---|---|
| Annual generation | ~25,500 kWh | ~25,500 kWh |
| Self-consumption | 50% | 75% |
| On-site value (27p/kWh) | ~£3,443 | ~£5,164 |
| Export value (7p/kWh) | ~£893 | ~£446 |
| Total annual benefit | ~£4,336 | ~£5,610 |
| Payback (after AIA at 25%) | ~5–6 years | ~6–7 years |
The key takeaway is simple: performance is not just about the system, but about how well it 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) lets your business deduct the full cost of the solar system from taxable profits in the year it is installed. As a result, 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.
| Scenario | Value |
|---|---|
| System cost (ex-VAT) | £32,000 (midpoint of typical range) |
| AIA tax saving at main rate (25%) | £8,000 |
| Net cost after tax relief (25%) | ~£24,000 |
| AIA tax saving at small profits rate (19%) | £6,080 |
| Net cost after tax relief (19%) | ~£25,920 |
💡 Did you know?
Rooftop solar installations are currently exempt from business rates increases until 2035. For a 30kW system, that can be a meaningful avoided cost which standard ROI models often leave out. Confirm the applicable corporation tax rate with your accountant — the main rate (25%) applies to profits above £250,000, and the small profits rate (19%) applies below £50,000.
Without tax relief, a system saving around £5,000–£6,000 per year is already a solid investment. With AIA, you are effectively investing closer to £24,000–£26,000 (at the 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 is about recovering energy you would otherwise lose. The system already produces around 25,500 kWh per year. The real 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.
| Usage pattern | Without battery | With battery | Financial impact |
|---|---|---|---|
| Daytime-heavy (clinic, school, retail) | ~65–75% | ~75–85% | Small uplift (~£500–£800/yr) |
| Mixed-hours (office, warehouse) | ~50–60% | ~70–75% | Moderate uplift (~£800–£1,200/yr) |
| Evening-heavy (restaurant, gym) | ~40–50% | ~65–75% | Strong uplift (~£1,200–£1,500+/yr) |
A typical 30kWh battery adds £12,000–£20,000 to the project. For daytime businesses, the additional savings are relatively small, so payback on the battery itself is slow. For evening-heavy businesses, the situation is different. A battery lets you use energy that would otherwise be exported at a low rate, which significantly improves overall system value. The simplest decision rule is this: if most of your electricity is used between 8am and 5pm, solar-only is usually the stronger financial choice. If your electricity use stays high in the evening, a battery becomes worth serious consideration. Many businesses therefore install solar first, monitor how much they export, and then decide whether storage will materially improve the outcome.
The Sizing Decision Most Businesses Get Wrong
At 30kW, most businesses don’t accidentally overspend — they accidentally undersize. This is not because they have done the maths wrong. Instead, they base the decision on what their electricity use looks like today, rather than what it will look like once the system is in place. Demand in most businesses doesn’t stay flat. Instead, it tends to creep up 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), a 30kW system will feel well-matched today. However, it may feel tight in a few years. Adding capacity later is rarely a simple extension. It can involve new design work, additional installation costs, changes to the inverter or layout, and a fresh G99 application for the extra capacity. 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. Instead, 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 on-site installation is not the complicated part. What matters is how the process is managed from the start. Because the system sits above the G98 threshold, it requires G99 grid approval before installation, and that approval — typically 6–12 weeks — is the main driver of the timeline. Allowing for approval, design and scheduling, most projects run around 10–16 weeks end to end, with only a few days of that spent on the roof.
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 is the usage. If the system is sized incorrectly at this stage, it 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 is not visible on site. The team designs the system around how much energy you can realistically use. That covers how the panels lay 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: G99 grid approval — the main timeline driver
Because a 30kW system sits above the G98 small-scale threshold, your installer submits a G99 application to your Distribution Network Operator before any installation begins. This typically takes 6–12 weeks and sets the overall timeline. Installation cannot start until the operator grants approval, which is exactly why it pays to begin the process early. Solar4Good manages this application for you as standard.
Step 4: Scheduling and preparation
Once approval is in place and the design is agreed, equipment is ordered and installation is scheduled. Site access is planned, and the project is prepared so the work can happen without interruption.
Step 5: Installation
In reality, this is the shortest and least disruptive part of the process. Panels, mounting systems and inverters go in 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 6: Commissioning and handover
Once installed, the team tests and connects the system. 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.
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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, keeps the engineering straightforward, and provides a clear financial return. The one thing to plan for is the G99 approval, which sets the timeline, so it is worth starting early.
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. It is also 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 to know about commercial solar in the UK.
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Frequently Asked Questions
Does a 30kW system need grid approval before installation?
Yes. A 30kW system sits well above the G98 small-scale threshold, so it needs a G99 application to your network operator before installation can begin. This typically takes 6–12 weeks and is the main reason to start the process early. Your installer manages the application for you.
How much can a 30kW system actually save my business?
For a daytime-heavy business, typically around £5,000–£6,000 per year, from a combination of on-site savings (at 27p/kWh) and SEG export payments (at a conservative 7p/kWh). If a significant portion of your usage is in the evening, savings will be closer to £4,000–£5,000 without battery storage. The real figure depends on when you use electricity, not just how much.
Sizing, batteries and timelines
How do I know if 30kW is the right size for me?
A good rule of thumb is your electricity spend. If you are spending around £8,000–£15,000 per year and most of your usage is during the day, 30kW is usually a strong fit. If you are closer to £20,000 or expect demand to grow, it is worth considering a larger system from the start to avoid undersizing.
Is it worth adding a battery at this size?
Only in specific cases. If your business already uses most of its electricity during the day, a battery won’t add much value and will extend payback. It becomes worthwhile when a significant portion of energy use happens in the evening. It also helps when you are exporting a large amount of unused solar at a low rate.
How long does the whole project take?
Around 10–16 weeks end to end. Most of that is the G99 grid approval (typically 6–12 weeks) plus design and scheduling. The on-site installation itself usually takes only a few days, and day-to-day operations continue as normal during it.
About the Author
Matthew
Solar Consultant with over a decade of UK solar experience, helping homeowners and businesses make clear, confident renewable energy decisions.
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Solar4Good Ltd · 79 College Road, Harrow, HA1 1BD · MCS: NAP/72775/25/4 · HIES: S4G/A/1484