MCS vs non-MCS: what you lose

What you actually lose

The bottom two rows are the ones people get wrong in the other direction. Non-MCS does not mean unregulated — it means one particular certification is absent, while the statutory requirements are untouched.

The export payment problem

This is usually decisive.

Ofgem’s SEG guidance states that for installations up to 50 kW, “applicants will be asked to demonstrate that their installation and installer are suitably certified”, and that this “may be a Microgeneration Certification Scheme (MCS) certificate” while recognising that other schemes may be equivalent — accredited “in accordance with EN 45011 or EN ISO/IEC 17065:2012”.

So it is not a statutory monopoly. But in practice the MCS certificate is the document suppliers ask for, and we have not been able to establish which alternatives any licensee actually accepts.

Work out what that costs you. On our figures a 4 kWp array in London generates about 3,676 kWh a year. With self-consumption around 14–23% without a battery, roughly 2,800–3,160 kWh would be exported. At even a modest export rate that is a recurring annual sum, forgone for the life of the system.

The disclosure you give up

Everything on what a good quote looks like flows from MIS 3002, which binds MCS contractors. A non-certified installer is not required to give you:

• the performance estimate in the prescribed format, with the Important Note
• the self-consumption estimate calculated to MGD 003
• the module layout drawing
• the sunpath diagram where shading applies
• the note telling you the site was assessed remotely

You can still ask for all of it, and a competent installer should be able to produce it. What you cannot do is point at a standard when they do not.

What does not change

Building regulations. A solar installation normally adds a new circuit, which is notifiable in England. An installer registered with a competent person scheme self-certifies; one who is not must notify building control before starting. See building regulations.

Network notification. G98 or G99 applies to the installation, not the installer.

Your consumer rights. The Consumer Rights Act, the cancellation regulations and section 75 all apply regardless.

Structural adequacy. The physics is indifferent to certification. What changes is that MIS 3002 requires the check; without it, you have to insist.

When non-MCS is defensible

A zero-export connection, where there is no export income to lose anyway.

An off-grid or outbuilding system not connected to the property’s main supply.

An installer you know, who can evidence the electrical work through a competent person scheme, produce a structural assessment, and notify the network operator properly.

Where no grant is in play and you are certain none will be.

That is a narrower set than it first appears — and note that three of the four still require the installer to do most of what MCS would have required, just without the certificate at the end.

If you already have a non-MCS installation

Establish what paperwork exists: building regulations certificate, electrical installation certificate, DNO notification. Those are the ones that matter legally and they are obtainable from the scheme, the authority and the network operator.

Ask a SEG licensee directly what evidence they would accept. The answer may be better than assumed.

Keep everything for the sale. The handover pack list is what a buyer’s conveyancer will ask for, and being able to produce everything except the MCS certificate is a much better position than being able to produce nothing.