What is MCS, and why does it matter?

Who actually runs it

Worth being precise, because “certification scheme” invites the assumption of officialdom.

MCS standards are copyright the MCS Charitable Foundation, a registered charity, and are published by The MCS Service Company Ltd on the Foundation’s behalf. The standards are drafted by working groups — MIS 3002 comes from MCS Working Group 2: Solar PV Systems — and MGD 003 was prepared with Advance Further Energy, the BRE National Solar Centre and the University of Loughborough.

Certification itself is done by independent certification bodies, not by MCS. An installer applies to a certification body, which assesses them; MCS runs financial and customer-treatment checks and holds the installer agreement.

MCS is also careful about the status of its own guidance. MGD 003 opens by saying it “is neither a mandatory MCS requirement, nor does it contain mandatory requirements, unless expressly stated as such in an MCS installation standard”.

What MCS certification gates

This is the practical answer to “does it matter”, and the answer is yes — through other people’s rules rather than its own.

Ofgem’s wording on the SEG requirement is worth reading closely, because “MCS or equivalent” is more open than it is usually presented:

For PV, wind and micro-CHP installations up to 50kW, applicants will be asked to demonstrate that their installation and installer are suitably certified.

And on alternatives, that certification “should be accredited in accordance with EN 45011 or EN ISO/IEC 17065:2012”. So MCS is the ordinary route, not a statutory monopoly. In practice suppliers ask for the MCS certificate because it is the document that exists.

What an MCS installation standard actually requires

Since MCS is the gate, it is fair to ask what passing through it obliges an installer to do. MIS 3002 is more demanding than its reputation suggests, and most of its requirements are things you can check for yourself.

Before you buy, you are entitled in writing to:

• A performance estimate in a prescribed table format: installed capacity in kWp, orientation in degrees from south, inclination from horizontal, postcode region, the kWh/kWp figure used, the shade factor, and the estimated annual output
• A self-consumption estimate calculated in accordance with MGD 003, stated both as a percentage of generation and in kWh, for the relevant occupancy archetype, and separately with and without battery storage
• Grid independence stated separately from self-consumption
• Manufacturers’ datasheets for the modules, the inverter, any module-level electronics and any battery
• A drawing of the proposed module layout
• The sunpath diagram used to calculate the shade factor, where shading is present and the MCS method was used
• Prescribed caveats, including a specific note where the site was assessed remotely rather than visited, stating that “actual performance may be significantly lower or higher”

That is a substantial disclosure package, and it is the most useful thing about MCS certification from a buyer’s point of view. Two of our other pages exist because of it: self-consumption explains the figure MGD 003 produces, and shading explains the shade factor and your entitlement to the diagram behind it.

What MCS is not

Not a government scheme. Government schemes rely on it. That is not the same thing, and any material implying official status is misleading.

Not an inspection of your installation. The certification body assesses the company’s processes and at least one compliant installation per technology. Yours is very unlikely to be the one assessed.

Not a warranty. MCS does not stand behind the work. Workmanship warranties come from the installer, and are worth exactly what the installer is worth.

Not insurance. An insurance-backed guarantee is a separate product that pays out if the company fails. If workmanship cover matters to you, that is the thing to ask about, not MCS.

Not a competence qualification for an electrician. Electrical work is governed by Part P and BS 7671, and by the competent person schemes. MCS sits on top of that.

Not a promise about the numbers. MIS 3002’s own performance estimate carries a caveat that the figure “should not be considered as a guarantee of performance”, and its shading methodology claims accuracy only “within 10% of the actual energy estimate stated for most systems.”

Checking a certificate

The MCS Installations Database is where certificates are raised, and it is the record that follows the installation rather than the company. Two practical points:

Get your certificate and keep it. Your SEG supplier is likely to ask for it, and a buyer’s conveyancer may ask years later. It is evidence about the property, not just about a transaction you have finished with.

Check the installer’s certification before signing, not after. Certification is a current status and can be withdrawn. What matters is that they held it when your work was done and that a certificate was raised for your job.

If the installer disappears afterwards, the certificate survives. It is a record of what was installed and by whom. Your SEG eligibility does not evaporate with the company. Your workmanship warranty probably does.

Where MCS is genuinely criticised

Setting this out because a page that only explains the scheme would be incomplete, and because these are the arguments a reader will meet elsewhere.

It certifies companies, not jobs. The assessment sample is small relative to the volume of installations a certified company then does.

It is a barrier to entry. Certification costs money and administrative effort, which excludes small competent firms and, some argue, favours volume operators.

It creates a lock-in through SEG. Because export payments effectively require it, an owner who used a competent non-certified electrician can find themselves unable to be paid for exports on a perfectly sound installation.

Its published evidence base is thin. There are no public figures on assessment failure rates or withdrawals, so the scheme’s effect on installation quality cannot be evaluated from outside.

None of that makes certification worthless. It makes it a specific and limited thing that is widely presented as a general assurance of quality — which is the gap this page exists to close.