GUIDE · FOR UK SOLAR INSTALLERS · 11 MIN READ

MIS 3002: The MCS Solar PV Standard, Explained for Installers

Every clause, date and figure below is sourced at the end. Not yet certified? Start with our guide to MCS certification for solar installers.

What MIS 3002 is and who it applies to

MIS 3002 covers MCS contractors who supply, design, install, set to work and commission grid-connected solar PV on permanent buildings, up to a maximum DC output of 50kWp. Scope is stated in DC kWp, so check the array, not just the inverter. MCS covers commercial contracts as well as domestic ones.

Read the verbs carefully: “must” is a legal requirement, “shall” is to be met in full, and “should” is to be met unless you can justify not doing so.

Which version applies to you

Both were issued on 18 March 2026. Yours depends on whether you've moved to the redeveloped scheme.

The March 2026 issues extended clause 3.5.5 (5.5.5 in v6.0) on mounting systems not certified to MCS 012. MCS says the redeveloped standards were streamlined but the actual requirements are unchanged. Clause numbers here are from MIS 3002:2025; v6.0 covers the same points in sections 5 and 6.

The documents that sit around it

The MCS performance estimate

Before the contract is awarded, the customer gets an estimate of annual generation worked out the MCS way (MCS 032 on the redeveloped scheme, Appendix B of MIS 3002 v6.0):

1. 1

   Add up the data-plate Wp of every module to get the array kWp.

2. 2

   Find the postcode zone from the table in the standard.

3. 3

   Measure the pitch (to the nearest 1°) and the orientation from due south (to the nearest 5°).

4. 4

   Look up kWh/kWp (Kk) for that zone, pitch and orientation in the MCS tables.

5. 5

   Work out the shade factor (SF). With a clear horizon and no shading, SF is 1.00.

6. 6

   Annual AC output (kWh) = kWp × Kk × SF.

The Kk tables are PVGIS data multiplied by 0.8. Shade is assessed on the MCS Sunpath chart (MGD 005, or Appendix A of MCS 032), which MCS expects to be within 10% of actual yield for most systems.

The estimate goes in MCS's prescribed table and must carry this text:

“Important Note: The performance of solar PV systems is impossible to predict with certainty due to the variability in the amount of solar radiation (sunlight) from location to location and from year to year. This estimate is based upon the standard MCS procedure is given as guidance only for the first year of generation. It should not be considered as a guarantee of performance.”

Extra wording is required where SF is below 1 (with another shading method, you commit to at least 90% of the estimated kWh) and where the site was evaluated remotely. Copy it word for word. Under v6.0, other estimates can be added but not given more prominence than the MCS figure. If your solar design software produces the MCS table, check it uses the current wording.

Self-consumption, with and without a battery

The estimate also gives self-consumption, PV only and with any battery quoted. The MCS method (MGD 003, and section 5 of MCS 032) uses look-up tables by occupancy archetype, annual consumption and generation.

It is not applicable to non-domestic buildings, and MGD 003 assumes 1,500–6,000 kWh a year of consumption and under 6,000 kWh of generation. Outside that, use a method no less valid; on a commercial job, the site's own consumption data is the obvious starting point. If you quote self-consumption with a battery and aren't certified to MIS 3012, make that clear.

Electrical design and the grid

Design to the IET Code of Practice (2nd edition) plus MIS 3002's additions and exceptions, with BS 7671 taking precedence in a conflict. Key clauses:

• Grid (3.1.5–3.1.6): G98 up to 16A per phase, G99 above, G100 where export is limited, judged on the aggregate AC output of all generators. 3kW of PV plus a 3kW battery on one single-phase supply is a G99 job. You notify the DNO.
• Surge protection (3.3.3): required unless the owner accepts the risk, even where BS 7671 doesn't demand it. Don't assume the inverter provides it.
• Earthing (3.3.2): if the array frame gets neither protective nor functional earthing, record why.
• DC connectors (3.6.3–3.6.4): correct tools, kept out of standing water. MCS says wrong crimping tools are a significant factor in failures and fires.
• Arc fault detection (3.6.7): enable it if the inverter has it.
• Voltage drop (3.6.8): minimise it, cut-out to inverter; around 1% for small domestic systems, up to 3% for larger ones or long runs.
• Metering and data (3.7): a generation meter readable without a tool, ladder or torch; fault notification within 48 hours; changed device passwords; IT permission on commercial sites.

The grid side has its own guides: G98 notification and limits, the G99 application for commercial solar and which DNO to apply to.

Roofs, mounting and fire

Modules must be listed on the MCS website, and systems above or integrated into a pitched roof must use kits certified to MCS 012, which tests wind uplift, fire classification (to BS 476-3 or CEN TS 1187 Test 4) and weathertightness. Where a job is outside MCS 012 or no certified system suits it, clause 3.5.5 allows another mounting system if it keeps the building compliant with Building Regulations (structure, fire, weathertightness) and you can evidence:

• a structural assessment and wind loading calculation for that system;
• that the customer was told to update their Fire Risk Assessment;
• how the roof's weathertightness was maintained;
• that the components are compatible, installed to the manufacturer's instructions.

Whatever the kit, you need to be able to show the roof's fire performance is unaffected (3.8.1). On pitched roofs (10° to 70°), a competent person checks the structure; anything unusual, under 30° or prone to snow build-up goes to a structural engineer. On metal roofs, check sheet thickness and fixings against wind uplift.

On flat roofs (under 10°), fixing to a solid deck should follow a condition survey and pull-out tests. Ballasted systems use BRE Digest 489 or test data for wind, a compatible slip layer, a friction coefficient of 0.3 unless tested, and a structural engineer's sign-off on the load. Layouts should leave access for maintenance and emergency services. These are survey questions, so build them into your commercial solar survey checklist, and check kit certification with your solar wholesaler.

Commissioning, handover and the MCS certificate

Commission to a documented procedure, and inspect and test to Section 16 of the IET Code of Practice (except 16.4). Both versions reproduce BS EN 62446-1 verification certificate and array test report templates. Complete Building Regulations notification before handover if it's yours to do.

• Current scheme (v6.0): a document pack and a signed handover document including the performance estimate. Register on the MCS Installation Database within 10 working days of commissioning, never before.
• Redeveloped scheme: share the Customer Commitment before the contract, follow MCS's Handover Checklists, and raise the MCS certificate within 30 calendar days of commissioning. The customer also gets any Building Regulations certificates and proof of DNO notification within 30 days of completion.

MIS 3002 job checklist

The main requirements by stage; clauses are MIS 3002:2025 unless noted. Not a substitute for the standard.

Common non-conformities

NICEIC, reporting MCS's own figures, listed the top solar PV non-conformities from 87 technical assessments in May 2025:

• No schematic at the point of interconnection.
• No Dual Supply label installed at the origin.
• Control switches and isolators not clearly identified.
• Inverter clearances don't meet the manufacturer's requirements.

Commercial jobs above 50kW

Above 50kWp the job is outside MIS 3002 and MCS. But MIS 3002 itself describes complying with the Electricity Safety, Quality and Continuity Regulations 2002, and following G99 or G100, as a legal requirement rather than an MCS one, so G99 applies as normal. For the Smart Export Guarantee, Ofgem's guidance says PV over 50kW and up to 5MW needs the installation certified but not the installer, and the export supplier decides how: ask it early.

The grid process is the same: see the G99 guide for commercial solar and how to apply to your DNO.

From compliance to commercial work

Once you're working to MIS 3002 and can take on G99 connections, the next job is finding business owners ready for a survey. If you're still setting up, see how to become a solar installer in the UK; if you're ready for work, compare how to get commercial solar leads and read how to sell commercial solar.

Solar Surveys UK books qualified commercial solar survey appointments with business owners for UK installers. You pay per booked appointment, with no retainer, from £400+VAT to £1,000+VAT per lead depending on system size (see how much commercial solar leads cost). Read how booked solar leads differ from form fills or see our commercial solar leads.

MIS 3002: FAQ