Commercial Solar PV Installation

From site survey to commissioned system — a complete guide to the commercial solar PV installation process, including DNO applications, MCS certification and monitoring.

What Commercial Solar PV Installation Involves

Commercial solar PV installation is a managed project, not a single event. From initial survey to operational system, the process involves structural assessment, electrical design, regulatory submissions, procurement, physical installation and commissioning — each stage requiring specialist expertise and coordination. Understanding the process helps businesses plan projects, manage expectations and select the right installation partner.

The key distinction between domestic and commercial solar PV installation is scale, regulation and engineering complexity. A commercial system of 50kW+ connects to the Distribution Network Operator under the G99 engineering recommendation, requires a protection relay and metering arrangement, and may need structural engineering certification of the mounting structure. These requirements mean that commercial solar installation should only be undertaken by MCS-certified contractors with specific commercial sector experience.

The Commercial Solar Installation Process: Step by Step

Stage 1: Site Survey and Feasibility (Week 1–2)

Every commercial solar project begins with a site survey. Our surveyors assess: available roof or ground area; roof structure and condition; roof orientation and pitch; shading from surrounding buildings, trees and rooftop obstacles; existing electrical installation (switchboard capacity, available space for inverter and metering); and proximity to DNO connection point.

Using irradiance modelling software (PVsyst or Helioscope), we model annual generation for the proposed array based on exact orientation, tilt angle, shading analysis and local climate data. The output is a feasibility report showing projected generation, self-consumption, annual savings, payback period and IRR.

Stage 2: System Design and Engineering (Week 2–4)

Commercial solar system design involves selecting panels, inverters, mounting hardware and cabling to maximise performance within physical and budget constraints. Key design decisions include:

The design is reviewed by a qualified electrical engineer and signed off before DNO submission. For systems over 100kW, a full electrical design package (single-line diagram, protection coordination study, metering schedule) is prepared.

Stage 3: DNO Application (Week 3–12)

All commercial solar systems over 3.68kW require notification to or application with the local Distribution Network Operator:

G99 applications require a protection relay (typically a Type A or Type B relay depending on connection voltage) and export metering. The relay protects the network from anti-islanding — ensuring the solar system disconnects instantly if the grid connection is lost, preventing energised cables in fault conditions.

DNO connection cost varies significantly by region, substation capacity and required reinforcement. In some areas, particularly rural locations and industrial zones with high existing embedded generation, reinforcement charges can add £10,000–£100,000 to project costs. We obtain a DNO pre-application assessment before design finalization to identify and budget for connection costs.

Stage 4: Procurement and Logistics (Week 6–14)

Panel and inverter procurement is managed against the installation programme. For projects over 100kW, we order from Tier 1 manufacturers (Longi, Jinko, Trina, Canadian Solar, SolarEdge) with verified manufacturing quality certifications (IEC 61215, IEC 61730, MCS approval). Delivery is coordinated with scaffolding (if required), crane (for heavy roof lifts), and site security arrangements.

All products used on MCS-certified commercial installations must be MCS-approved or MCS-recognised. The MCS products database lists approved panels, inverters, batteries and mounting systems. Using non-approved products invalidates MCS certification and SEG eligibility.

Stage 5: Physical Installation (3–5 Days for 100kW)

Installation begins after DNO approval and scaffold/access equipment is in place. The typical sequence for a roof-mounted commercial system:

• Day 1: Scaffold erect (if required), surveying and marking anchor/rail positions, first rail fixing
• Day 2: Complete rail installation, begin panel lifting and placement
• Day 3–4: Panel installation complete, DC cabling from strings to inverter location
• Day 4–5: Inverter installation, AC connection to switchboard, metering and protection relay installation
• Day 5: Testing, commissioning, monitoring system configuration, handover documents

For larger systems (200kW+), installation typically takes 5–10 working days with a larger crew. Business operations continue during installation on all but the most complex projects. Temporary power outages for switchboard connection work are typically less than 2 hours and can be scheduled outside business hours.

Stage 6: Commissioning and Handover

Commissioning involves testing every string for open-circuit voltage and short-circuit current, verifying protection relay operation, testing DNO export limiting (if required) and confirming monitoring system data transmission. A formal MCS certificate is issued, triggering SEG eligibility.

Handover documentation includes: MCS installation certificate; electrical installation certificate (BS7671); inverter manual and monitoring login details; G99 connection agreement; structural engineer's report (if applicable); operations and maintenance manual; warranty documentation for all components.

Choosing a Commercial Solar PV Installer

MCS certification is the minimum standard for commercial solar installers in the UK. Beyond MCS, commercial projects benefit from contractors with:

• NICEIC or ECA registration (Part P electrical work)
• Minimum 5 years commercial solar installation experience
• Public liability insurance of at least £5 million
• Professional indemnity insurance of at least £1 million
• CHAS or Constructionline supply chain accreditation
• References from comparable commercial installations (same system size, building type)
• In-house electrical design and DNO application capability (not subcontracted)

Our team includes MCS-certified designers, NVQ-qualified installation engineers, Part P electrical contractors and a CHAS-registered principal contractor. We carry full £10 million public liability, £1 million professional indemnity and employer's liability insurance across all projects.

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