What MCS certification covers, and what it does not

Almost every conversation about a heat pump or a solar array in Britain arrives, sooner or later, at three letters. A grant application asks for an MCS certificate. An installer's van carries the logo. A quotation mentions it in a way that suggests it settles something, and what it settles is narrower than the logo implies.

What the scheme is

MCS stands for the Microgeneration Certification Scheme. It began in 2007, and it does two separate jobs that are easy to confuse.

The first is product certification. A heat pump or a solar module can be listed by MCS once it has been tested against a product standard and the test results have been checked. The listing is a statement that the equipment does what its manufacturer says it does, measured in a laboratory to a method everyone uses, so that two heat pumps quoted for the same house can be compared on the same terms.

The second is installer certification. A company can be certified to install one or more technologies once a certification body has audited it: looked at its quality management, checked that the people doing the work hold the qualifications the scheme requires, inspected some of its finished installations, and satisfied itself that the company follows the installation standards. That audit is repeated, and the certificate can be withdrawn.

The scheme is run by MCS Service Company, which is owned by the MCS Charitable Foundation. It does not do the auditing itself. That is done by certification bodies which hold accreditation from UKAS, the national accreditation body, against the international standard for product certification schemes. The chain matters: it means the people checking installers are themselves being checked.

The standards behind it

MCS publishes its standards openly, which is unusual and useful. Anyone can read exactly what an installer has agreed to do, and the documents fall into a few families.

Installation standards, prefixed MIS

What must be done on site. MIS 3002 covers solar photovoltaic systems; MIS 3005 covers heat pumps and is split between a design part and an installation part. These are the documents that say a heat pump must be sized from a room-by-room heat loss calculation, or that a solar array must be estimated using a particular method.

Product standards, prefixed MCS

What equipment must demonstrate before it can be listed. MCS 007 is the heat pump product standard; MCS 012 covers the mounting kits that hold solar panels to a roof.

Guidance documents, prefixed MGD

Methods and reference data. MGD 003 estimates how much of a solar system's output a household will actually use. MGD 005 is the shading assessment. MGD 007 gathers together the reference tables: hot water cylinder sizing, mean air temperatures, the Heat Emitter Guide.

Scheme requirements

MCS 001, in two parts, sets out what a certified contractor must have in place as a business, and what its people must be qualified in.

Guidance documents are not mandatory in themselves. They become mandatory when an installation standard points at them and uses the word shall.

What certification is evidence of

An MCS certified installation carries three things a non-certified one does not.

A design done to a published method. The heat pump was sized from a calculation, not from the size of the boiler it replaced. The solar estimate came from a national dataset and an arithmetic anyone can repeat, not from a figure someone felt was about right.

A company that has been audited, and can be audited again. If the work is poor, there is somebody to complain to who has the power to act, which is not true of a trader with a website.

A certificate on a national database, registered after the work is done. That certificate is what a grant scheme wants, what an export tariff supplier wants, and what a purchaser's solicitor will ask for in fifteen years' time.

What it is not

It is not a guarantee that the work is good. Certification tests a system for producing good work; it does not inspect every job. A certified installer can still make a bad job of an installation, and some do. Certification changes what the customer can do about it afterwards.

It is not a warranty. Equipment warranties come from manufacturers and workmanship warranties from the installer. MCS certification of a company that later goes out of business does not make anybody else responsible for its warranties, which is why insurance-backed guarantees exist separately.

It is not a price control. Two certified installers can quote figures that differ by half, and both can be following the standards exactly. What the standards constrain is the method behind the numbers, not the margin on top.

It is not a judgement about whether the technology suits your house. The standards require the installer to survey, calculate and tell you what they found. They do not require the installer to talk you out of it, though a good one will.

Using it well

The most useful thing about MCS from a householder's side is not the logo. It is that the standards are published, so the calculations behind a quotation are checkable. If a quotation says a house needs a 12 kW heat pump, there is a room-by-room heat loss calculation somewhere that either supports that or does not, and you are entitled to see it. If a quotation promises 4,200 kWh a year from a roof, that figure came from a capacity, a postcode zone, a pitch, an orientation and a shade factor, and the same five numbers put through the same table should give the same answer on anybody's desk.

Check the certificate is current, and for the technology being installed. A company certified for solar PV is not thereby certified for heat pumps. The MCS website carries a searchable list of certified contractors, and the certificate number on a quotation can be looked up against it.