MIS 3002 solar PV standard

MIS 3002 is the MCS installation standard for solar PV systems. It covers the supply, design, installation, setting to work and commissioning of systems serving permanent buildings, normally connected in parallel with the distribution network, with a maximum DC output of 50 kWp.

It governs an MCS-certified solar installation. It is not a general law requiring every PV system to be MCS certified, and it does not replace Building Regulations, planning, BS 7671 or the DNO connection process.

Which edition is current?

There are two MCS installer-scheme tracks during the transition to MCS:2025. As at 22 July 2026:

installers still operating under the previous scheme use MIS 3002 Issue 6.0, dated 18 March 2026 and mandatory on that track from 18 June 2026
installers certified to MCS:2025 use MIS 3002:2025 Issue 2.0, also dated 18 March 2026

The technical installation requirements are closely aligned, but the documents are structured differently. The previous-scheme Issue 6.0 still contains pre-sale, performance-estimate, handover, maintenance and competence sections. Under MCS:2025, some of those business and consumer-facing requirements sit in separate scheme documents, while MIS 3002:2025 concentrates on technical design, installation and commissioning.

The installer’s scheme version and the MIS 3002 edition are separate references. Referring only to “the current MCS standard” is ambiguous during the transition.

The main technical hierarchy

MIS 3002:2025 requires the PV system to follow the second edition of the IET Code of Practice for Grid Connected PV Systems, with the additions and exceptions stated in MIS 3002.

If a specific technical conflict arises, the latest BS 7671 takes precedence. The standard also requires the applicable legislation to be met and recognises that the legal position differs across England, Wales, Scotland and Northern Ireland.

The hierarchy is therefore:

applicable law and building regulations
BS 7671 for the electrical installation
the MCS scheme requirements and MIS 3002
the IET PV Code of Practice, as modified by MIS 3002
manufacturer instructions, unless a justified higher-level requirement controls

MCS itself warns that compliance with MIS 3002 does not confer immunity from legal obligations.

Building and roof assessment

The MCS contractor must ensure that the building is assessed by a competent professional experienced in solar PV systems. The work must not compromise the building’s compliance with Building Regulations, and a suitable risk assessment must be completed before site work begins.

For a pitched roof, MIS 3002:2025 requires a suitably competent person to check that the structure can withstand the loads imposed by the array. Its table gives assessment methods for common timber-trussed and traditional gable-ended roofs.

A qualified structural engineer is required where the roof is unusual or there is doubt. The standard’s examples include:

a form not covered by its typical-roof table
structural distress
post-construction changes such as removed or notched timbers or a heavier roof covering
a pitch below 30 degrees
layouts with increased potential for snow build-up, such as dormers, valleys or parapets
traditional cut roofs with hips or valleys
asymmetric duo-pitched roofs

This is more precise than saying that every hipped roof automatically needs the same response in every construction. The actual roof form, construction and condition control the assessment.

For a ballasted flat-roof system, the standard expressly requires a qualified structural engineer to confirm that the roof can withstand the array and ballast loads. It also sets rules for wind coefficients, slip layers, sliding resistance and the evidence needed where a coefficient of friction above the default is used.

Mounting products and alternatives

PV above or integrated into a pitched roof normally uses a mounting product tested and certified to MCS 012. Components must be approved to work together, and any restrictions tying a certified mounting system to named PV modules have to be observed.

MIS 3002 also allows a non-MCS 012 mounting system where the installation is outside the scope of MCS 012 or no suitable certified system is available. This is not a paperwork-free exception. The contractor must retain evidence addressing:

structural assessment and wind loading for the actual system
continued compliance with relevant structural, fire and weather-resistance requirements
the fire-risk assessment information given to the customer
roof weather-tightness after installation
component compatibility
installation to the instructions for every component

The 2026 revision expanded this clause. Calculations from a manufacturer, structural engineer or suitable software can form part of the evidence, but they must be linked directly to the actual design and installation; a generic output is not compliance by itself.

Layout, fixings and durability

The standard says module layout should allow access for maintenance and emergency services. On a domestic pitched roof, modules should not be within 400 mm of an edge unless specific measures address the higher wind uplift and associated risks, including secure ridge tiles, drainage, snow shedding and wind noise.

Tiles or slates may need appropriate notching or flashing so that roof hooks do not leave new displacement gaps. Metal roof sheets and their connection to the main structure must be checked where the array and brackets introduce extra uplift.

DC connectors should be kept out of standing water, assembled with the correct tools and procedures, and installed without losing the required ingress protection. These small details are important because a system can have compliant headline products but still fail at its connectors, cable entries or roof interface.

Electrical and DNO requirements

MIS 3002:2025 makes the MCS contractor responsible for following the appropriate G98, G99 and, where export is limited, G100 requirements. It also says the contractor is to undertake the DNO notification or application.

The G98/G99 decision uses the aggregate AC output of all generators on the connection, not just the new PV array. Existing PV and battery inverters therefore have to be included. The dedicated grid-connection entries contain the current routes and thresholds.

MIS 3002 also requires a means of recording and displaying total AC generation. Where a meter is used for billing or incentive payments, storage imports and exports must not corrupt the relevant measurement.

Pre-sale performance information

MCS solar pre-sale information includes a standardised generation estimate. Under the previous installer scheme, the calculation sits within MIS 3002 Issue 6.0. Under MCS:2025, it sits in the separate solar PV Pre-sale Information and System Performance Estimate Standard.

The distinction is administrative rather than an excuse to omit the estimate. The customer should still receive the standard MCS result, its site assumptions and any separate proprietary model in a form that does not disguise uncertainty. The performance-estimate entry explains the calculation in detail.

Before contract, the useful technical information includes the proposed module layout, module and inverter details, system capacity, shading assumptions, expected generation and any storage or module-level electronics included in the design.

Commissioning and handover

The system must be commissioned through a documented procedure confirming that it is safe, matches the standard and manufacturer requirements, and operates in accordance with the design. MIS 3002:2025 calls for inspection and testing against the PV Code of Practice and includes model verification and array test records adapted from BS EN 62446-1.

The handover evidence should allow another competent person to understand what was designed, installed and tested. It should include:

final array layout and system schematic
installed product details and warranties
design and structural evidence
performance estimate and its assumptions
electrical inspection and test results
PV array verification and commissioning records
DNO application, acceptance or notification evidence
operating, isolation, fault and maintenance instructions
Building Regulations and planning records where applicable
the MCS installation certificate

An MCS certificate is the top-level scheme record. It does not replace this underlying evidence.

MCS installation standards
MCS
MCS 012 solar mounting standard
MCS PV performance estimates
Shading analysis
Flat roof ballast systems
DNO notification for PV
PV commissioning pack
BS 7671 IET Wiring Regulations