Ben Brading 7 min read

How commercial solar panel installation works

Installing commercial solar panels is one of the most effective ways for businesses to reduce energy costs, improve sustainability credentials, and protect against rising electricity prices.

However, the process is complex, requires regulatory approvals, and typically takes several months.

This guide provides a clear, step-by-step overview of the commercial solar installation process, helping you understand what to expect at each stage.

Here’s what we cover:

What is commercial solar panel installation?
What to consider before installing commercial solar panels
System sizes for commercial solar panel installation
Commercial solar panel installation process
Commercial solar battery installation

What is commercial solar panel installation?

A commercial solar installation is the process of designing, sourcing, and setting up a solar photovoltaic PV system that generates electricity at a business site.

Unlike home systems, commercial setups are usually larger, built to meet higher energy demands, and designed to work with more complex electrical systems already in place.

What to consider before installing commercial solar panels

Before speaking to a professional installer, there are a few key points your business can consider to assess the suitability of a commercial solar installation.

Structural considerations

A roof-mounted commercial solar panel installation adds a weight of 10–25 kg/m² for 25+ years, so it is essential to ensure your building can safely support this load.

Before proceeding with a commercial solar installation, it is important to consider the following factors that may make the installation more challenging:

Asbestos sheet roofs – These often need to be replaced if this area is to be used for mounting commercial solar panels.
Roofing in poor condition – Deteriorating roof spaces may not be able to support mounting systems securely.
Timber-frame roofs – Timber-framed roofs, common in older buildings, may have a lower load capacity.
Limited access – Roofs without ladders or access hatches can make it difficult for installers to work safely, increasing the need (and cost) of scaffolding.

On-site power usage profile

An investment in a commercial solar panel installation is likely to be most effective where:

Peak daytime consumption – A large proportion of electricity is consumed during daylight hours, when solar panels generate the most power.
Consistent consumption – The more stable your power usage profile, the more efficiently solar panels can reduce your electricity bills.

The initial consultation phase will review the on-site power usage profile of your business to determine the feasibility of on-site solar generation.

Financial viability

Commercial solar panel installations require a significant upfront investment, which should pay for itself through reduced energy costs over five to ten years.

For your business to benefit from this investment, it will need to continue occupying the property in the long term.

Visit our in-depth guide to the cost of commercial solar panel installations for more information.

An easier step towards lowering energy bills is to use our business electricity comparison service to find a cheaper tariff.

System sizes for commercial solar panel installation

The number of solar panels in a commercial solar installation is typically determined by the space available or by how much electricity your business consumes on site.

Below, we describe how to do a high level estimation of each. The first step of a commercial solar installation is a feasibility study, which proposes a system size based on a formal review of your business property and power consumption.

Available space

Available space is often the main limiting factor in a commercial solar installation.

Each standard panel requires approximately 2 square metres of space, which is equivalent to 21.5 square feet.

To estimate how many panels you can install, divide your available space by these dimensions.

Electricity consumption

Assessing how much solar power your business can utilise each year is important. While it is possible to export excess electricity back to the grid, the rates received under the Smart Export Guarantee are significantly lower than import business electricity prices.

This means the optimal commercial solar setup should produce approximately the same amount of power that is consumed on-site.

Here is an approximate calculation for determining the optimal number of standard commercial solar panels:

Annual business energy consumption on-site in kWh ÷ Expected annual power output per standard panel (500 kWh)

Using this calculation, a small business energy customer consuming 15,000 kWh per year requires 30 commercial solar panels.

Commercial solar panel installation process

Commercial solar installation takes two to four months and includes a site survey, design and engineering, DNO approval, installation, and final commissioning. This section explains what to expect at each stage.

Our step-by-step process for commercial solar installation is based on the following key assumptions:

The system will use roof-mounted solar panels.
The majority of the generated power will be used on site rather than sold with a solar PPA.
The property is connected to the local grid.
Planning permission is not required (the property is not listed or located in a conservation area).

Initial consultation and feasibility study

An initial consultation for a commercial solar installation determines whether solar is viable at your property, recommends an appropriate system size, and provides a detailed cost quotation.

A commercial solar installation provider will review:

Recent business electricity bills
On-site business energy consumption
Consumption patterns from business energy monitoring software
Half-hourly electricity meter data for energy-intensive properties
The pitch and orientation of the roof space
The structural integrity of the roof space
The capacity of your current business electricity connection

💡 Where roof load-bearing capacity is uncertain, a structural survey may be required before finalising the system design or quotation.

A commercial solar installer will present their findings in a solar proposal document that includes:

A recommended system size in kW and number of panels
Recommended panel types (monocrystalline/polycrystalline)
Estimated commercial solar installation cost
Output, savings, and ROI forecast
Estimated project timeline

To proceed with the installation, you’ll need to formally commit to a commercial solar installer with a contract.

DNO approval

Commercial solar panel installations typically require approval from the local Distribution Network Operator (DNO), the company the operates the electricity grid in your area.

The approval, called a G99 application, is required where the installation exceeds:

Single-phase electricity supply – 3.68 kW (approximately 9 standard panels)
Three-phase electricity supply – 11 kW (approximately 27 standard panels)

The DNO approval process is required even if the system is designed to only occasionally export power back to the grid using a Smart Export Guarantee tariff.

Your installer will prepare electrical schematics and submit the G99 application to your local DNO. The standard review process takes four to eight weeks for the DNO to approve the installation.

Approval of the commercial solar installation may be conditional on:

Export limitations – A requirement to install an export limitation device.
Network reinforcement – Approval may be subject to you covering the cost of local network reinforcement.

If your approval is subject to network reinforcement, this work can take several months before you can proceed with your commercial solar installation.

Commercial solar panel design

While awaiting DNO approval, your installer will prepare a fully engineered, build-ready plan for your installation based on an in-person site survey.

The designs will include:

Detailed schematics showing how the system will integrate with the existing electrical infrastructure.
A panel placement plan, including the pitch and orientation of your panels for the mounting system.
Structural calculations demonstrating that the roof can bear the added weight of the panels.
Component specifications for panels, mountings, and inverter.

You’ll receive a copy of the final design pack for review and approval. Upon approval, your installer will confirm an installation date for your panels.

Installation of panels and electronics

The physical installation work required for your solar panels depends on the size and complexity of the system, but typically involves the following activities:

Preparing scaffolding to allow roof access.
Installing the panel mounting system.
Installing the panels onto the mounting system.
Installing a solar inverter.
Wiring the panels and installing isolation switches.
Connecting to the mains electrical distribution board.
Configuring a monitoring system for output tracking and fault detection.

Near the end of the installation process, a temporary interruption of electrical power will be required to connect the panels to the mains distribution board.

Commissioning, testing and go-live

Once the installation work is complete, an electrical engineer will test the system for correct operation, protection compliance, and performance.

An Electrical Installation Certificate (EIC) is issued to confirm that the installation work meets UK wiring regulations.

G99 commissioning documentation is prepared by the installer and submitted to the local DNO, providing evidence that the solar installation has been completed in accordance with the approved plans.

Once these commissioning and testing steps have been completed, the system can be energised.

At go-live, we recommend signing up with a business energy supplier that offers a Smart Export Guarantee (SEG) tariff, allowing you to sell back any unused excess power. Compare business energy prices with our free expert service today.

Commercial solar battery installation

Adding a lithium-ion solar battery to a commercial solar installation is an excellent way to increase self-consumption of generated electricity and minimise peak electricity prices and maximum demand charges.

A solar installer can recommend the specifications of a commercial solar battery, including:

Power capacity (kW) – How quickly the battery can charge and discharge
Energy capacity (kWh) – How much energy the battery can store

Most commercial solar batteries are installed with a separate inverter, allowing the battery to charge from both the grid and the solar panels, and enabling independent control via an Energy Management System.

Commercial solar batteries are typically floor-mounted in a temperature-controlled plant room.

Find out more in our guide to commercial solar batteries.

FAQs about commercial solar panel installation

Here we answer common questions about the process of commercial solar panel installation.

Do I need planning permission for commercial solar panels?

In most cases, commercial solar panels are permitted under Permitted Development Rights and therefore do not require planning permission. However, you may need permission if:

The building is listed or located in a conservation area.
Panels will project significantly from the roof.
The installation is ground-mounted.

What’s the lifespan of a commercial solar system?

Commercial solar systems are designed to last between 25 and 30 years, with the panels typically covered by a performance warranty of 25 years.

Inverters require more frequent replacement, usually lasting between 10 and 15 years.

How much roof space do I need?

A standard commercial solar panel requires approximately 2 square metres (21.5 square feet) of space.

The number of panels needed depends on the electricity consumption of your commercial property. A single panel will produce, on average, 1.5 to 2 kWh per day in Britain.

Can I install solar on a leased building?

Yes, but only with the landlord’s written permission.

You may also need to amend your lease to cover:

Roof access rights.
System ownership and maintenance.
Removal terms at the end of the lease.

How long does a commercial solar installation take?

The full commercial solar installation process typically takes 2 to 4 months from contract to commissioning, broken down into the following stages:

Design, approvals, and DNO consent: 4–12 weeks
Equipment ordering and preparation: 2–3 weeks
On-site installation: 1–3 weeks

Larger or more complex projects may take longer, particularly if grid upgrades or planning permission are required.

Will installation disrupt business operations?

Most of the physical work for a commercial solar installation takes place on the roof, so it is unlikely to disrupt day-to-day operations.

A temporary power outage will be required to connect the system to the mains distribution board, but in larger buildings, this is usually isolated to specific areas.