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The Redeveloped MCS Scheme: What's Changed for Heat Pump Standards?

The Microgeneration Certification Scheme (MCS) is undergoing one of the most significant changes in its history. The redeveloped MCS:2025 installer scheme introduces revised certification arrangements, Technical Supervisor responsibilities, risk-based assessments and new consumer-protection requirements.

For heat-pump installers, these changes affect much more than certification paperwork. They influence how businesses demonstrate technical competence, manage projects and take responsibility for completed installations.

The transition is already underway, but not every MCS installer is operating under the redeveloped scheme.

This guide explains the changes, the latest heat-pump standards and what installation businesses should be doing to prepare.

Last verified: 19 October 2026.

QUICK SUMMARY

Quick summary: Existing MCS installers are being transitioned to MCS:2025 in phases, with the published transition period ending on 31 March 2027. Updated heat-pump standards were approved for Boiler Upgrade Scheme purposes in September 2026. Installers must establish which scheme applies to their business, maintain suitable technical supervision and continue meeting the relevant design, installation and consumer-protection requirements.

What Is the Redeveloped MCS:2025 Scheme?

MCS is the UK certification scheme for small-scale renewable energy technologies, including heat pumps, solar PV and solar thermal systems.

Its purpose includes establishing technical standards, certifying installers and products, and supporting consumer confidence.

The redeveloped installer scheme, known as MCS:2025, changes how installer businesses are assessed and how their responsibilities are structured.

The intention is to place greater emphasis on the quality of delivered installations and on business processes appropriate to the way an installer operates.

Six important areas have changed.

Area	Main change
Certification	Redeveloped Installer Operating Requirements and Installer Agreement
Assessment	Operating scenarios and risk-based surveillance
Technical responsibility	Defined Technical Supervisor role
Standards	Updated and scheme-specific technical documents
Consumer protection	MCS Customer Commitment and revised complaints arrangements
Business controls	Requirements proportionate to operating activities and complexity

The redevelopment doesn’t remove the need for technical calculations, installation records or competent engineering decisions.

Instead, it changes the framework within which installers demonstrate that they can deliver compliant installations consistently.

MCS Transition Timeline — 2025 to March 2027

One of the most important points is that MCS:2025 wasn’t automatically adopted by every certified installer when the new documents were published.

The transition takes place through MCS certification bodies.

January 2025 — Redeveloped Scheme Documents

The initial MCS:2025 framework was published, introducing the new Installer Operating Requirements, Customer Commitment and associated scheme documentation.

Publication of these documents did not mean that all existing installers immediately transferred to the new scheme.

February 2026 — Phased Transition

MCS’s published transition arrangements provide for certification bodies to move their existing installer members across in phases from February 2026.

Individual businesses must complete the relevant checks and certification arrangements before being recognised under the redeveloped scheme.

September 2026 — Updated Approved Standards

On 29 September 2026, the Department for Energy Security and Net Zero updated the list of technical standards approved for the Boiler Upgrade Scheme in England and Wales.

This included revised heat-pump design standards and MCS:2025 versions of existing standards.

31 March 2027 — Published Transition Endpoint

MCS’s published phased-transition period runs to 31 March 2027.

Businesses should follow the current instructions and timetable issued by their certification body rather than assuming that the published endpoint is their individual transition date.

The key distinction: An installer still certified under the previous scheme must continue meeting that scheme’s requirements until their transition is formally completed.

For current arrangements, see the official MCS guide to moving over to the redeveloped scheme.

Which MCS Heat Pump Standards Apply in 2026?

The technical standards deserve particular attention because the previous and redeveloped schemes have different document references.

The government’s updated Boiler Upgrade Scheme standards notice, published on 29 September 2026, includes the following approved versions.

Standard	Approved version
MIS 3005-D — Heat Pump Design	Version 3.0
MIS 3005-D:2025 — Heat Pump Design	Version 2.0
MIS 3005-I — Heat Pump Installation	Version 1.0
MIS 3005-I:2025 — Heat Pump Installation	Version 1.0
MCS 007 — Heat Pump Product Standard	Version 8.0

Source: GOV.UK — Notice of Approved Standards, updated 29 September 2026.

These standards serve different purposes.

MIS 3005-D addresses heat-pump system design requirements.

MIS 3005-I addresses installation requirements, including relevant installation, commissioning and handover responsibilities.

MCS 007 concerns heat-pump product certification.

The documents carrying the :2025 designation relate to the redeveloped scheme and shouldn’t be treated as interchangeable with the corresponding previous-scheme documents.

The installer needs to establish the versions applicable to its certification arrangements and the project concerned.

The September government notice confirms approval for Boiler Upgrade Scheme purposes in England and Wales. It should not be interpreted as a universal change to every certification requirement across the UK on that date.

The standards themselves were published before the September notice.

What About Air-to-Air Heat Pumps?

The updated design standards include provisions covering air-to-air heat pumps.

This reflects the expansion of the technical framework to accommodate a wider range of heat-pump technologies.

However, the inclusion of air-to-air systems in a design standard doesn’t automatically establish that every product or installation is eligible for a grant.

Relevant product certification, installer certification, performance and scheme eligibility requirements must also be satisfied.

What Has Changed for Heat Pump Design?

The redeveloped MCS scheme retains the importance of a technically sound heating-system design.

For an air-to-water installation, the design process still needs to establish the building’s heating requirements and demonstrate that the proposed system can meet them.

Important considerations include:

Room-by-room and whole-property heat loss.
Appropriate indoor and outdoor design temperatures.
Heating emitter output.
Required design flow temperature.
Heat-pump capacity at the relevant operating conditions.
Domestic hot-water requirements.
Hydraulic arrangements and water flow.
System performance estimates and supporting documentation.

The standards establish applicable technical requirements. The design itself must demonstrate how those requirements have been addressed for the individual project.

This is where a distinction between software output and engineering judgement becomes important.

A heat loss report may be generated quickly, but incorrect construction assumptions can still produce an incorrect heating requirement.

Similarly, selecting a heat pump from a manufacturer’s nominal kW rating doesn’t establish whether it can meet the required design load.

The technical documents need to tell one consistent story, from the property survey through to the final equipment selection.

For a detailed breakdown of the supporting information, read What Should an MCS Heat Pump Design Pack Include?

The New Technical Supervisor Requirements

The redeveloped scheme establishes a defined Technical Supervisor role.

The Technical Supervisor takes overall responsibility for the safety, technical standard and quality of the installation assigned to them under the relevant scheme requirements.

A suitably competent person must hold an appropriate current qualification or recognised personnel certification.

Under MCS:2025, each installation registered on the MCS Installation Database must have an assigned Technical Supervisor.

The business must also have sufficient supervision arrangements for the scale and complexity of its work.

What Does the Technical Supervisor Actually Do?

The responsibility is broader than signing a completed document.

Appropriate supervision can involve:

Ensuring personnel undertaking the work are competent.
Making sure applicable technical requirements are understood.
Overseeing the quality of installation activities.
Checking that relevant installation evidence is available.
Ensuring changes are appropriately reviewed.
Confirming that the completed installation meets the required standards.

The degree of direct involvement will depend on the work, the individuals involved and the business’s supervision arrangements.

For example, a sole trader who surveys, designs, installs and commissions their own systems may operate differently from a larger business employing several installation teams.

An external heat-pump designer doesn’t automatically become the installer’s Technical Supervisor.

A specialist designer can produce calculations and supporting technical documents, but the certified installation business retains its relevant certification responsibilities.

The supervisor’s role must be established through the applicable MCS requirements and the business’s formal arrangements.

How Do Risk-Based MCS Assessments Work?

One of the redevelopment’s main changes is the assessment framework.

Rather than applying exactly the same business-control expectations to every installer, the scheme uses operating scenarios reflecting the size, complexity and nature of the business’s activities.

The Installer Operating Requirements identify scenarios A to D.

These help determine which processes and controls the business needs to demonstrate.

Assessment still includes technical inspection, but it also examines how the installer manages its work.

Certification bodies may undertake:

Service-delivery checks: Reviewing the processes, records and controls used to deliver installations consistently.

Site assessments: Checking technical installation work against the relevant standards and performance-estimate requirements.

The wider assessment and surveillance approach is risk-based.

However, this doesn’t mean a business with a good reputation automatically receives fewer inspections or that maintaining records becomes optional.

A company must still demonstrate effective processes for competence, design, installation quality, customer protection and project documentation.

The objective is to make the assessment proportionate while maintaining technical standards.

Do MCS Installers Still Need RECC or HIES Membership?

This is one of the most commercially significant questions arising from the redevelopment.

Under MCS:2025, separate RECC or HIES consumer-code membership is no longer mandatory as a condition of certification.

However, the position depends on which scheme the installer currently operates under.

Previous MCS scheme	Redeveloped MCS:2025
Membership of an approved consumer code remains required	Separate consumer-code membership is not mandatory
Previous consumer-protection arrangements continue	MCS Customer Commitment and redeveloped arrangements apply
Requirements remain until formal transition	New obligations apply following successful transition

An installer that has not yet transitioned should not cancel its consumer-code membership simply because the redeveloped scheme exists.

RECC or HIES membership may also remain useful voluntarily for businesses that value the additional services or protections.

What About the Boiler Upgrade Scheme?

The distinction is also relevant to BUS applications.

Ofgem’s current Installer Guidance, Version 5.1, recognises the redeveloped MCS:2025 scheme within the applicable consumer-protection arrangements.

Installers operating under the previous MCS scheme must continue satisfying its approved consumer-code membership requirements.

The correct position must be established before making decisions about cancelling membership or submitting grant applications.

See the current Ofgem Boiler Upgrade Scheme Installer Guidance.

What Has Changed for Consumer Protection and Complaints?

The redeveloped scheme introduces the MCS Customer Commitment as a central part of an installer’s responsibilities.

It covers the standards of service and consumer protection expected when supplying and installing certified systems.

Important areas include customer information, quotations, contracts, communication, installation handover and complaints.

The redeveloped framework also includes requirements concerning approved financial protection.

Installers are required to arrange an appropriate MCS-approved financial-protection product for their customers in accordance with the applicable scheme rules.

This is not simply a replacement label for RECC or HIES membership.

Businesses need to understand the actual Customer Commitment and financial-protection obligations applying to their certification.

What Happens When a Customer Complains?

The complaint-handling arrangements depend on which MCS scheme applied when the installation was carried out.

During the transition, some installations will have been completed under the previous scheme and others under MCS:2025.

The relevant consumer-code membership, certification body and MCS complaints process may therefore affect how a complaint is handled or escalated.

It would be misleading to say that every complaint now follows one identical route.

For homeowners, the important message is to retain their contracts, correspondence, technical documents, commissioning records and certification information.

For installers, it reinforces the importance of accurate records, clear communication and fair complaint handling.

Do Installers Still Need Design Records and Office Procedures?

Yes.

The redeveloped scheme changes the assessment framework, but it doesn’t remove the need for effective project administration.

Installers still need records demonstrating that the required work was designed, installed, checked and handed over appropriately.

That can involve:

Property surveys and supporting evidence.
Heat loss calculations and design assumptions.
Equipment and emitter selections.
Technical drawings and relevant installation instructions.
Current design revisions.
Competence and supervision records.
Installation and commissioning information.
Customer contracts and handover documents.
Complaints, changes and corrective actions where relevant.

The required business controls should suit the operating scenario and actual activities of the installer.

For smaller firms, this doesn’t necessarily mean employing a dedicated compliance administrator or maintaining an unnecessarily complicated document-management system.

It does mean having a reliable way to identify current documents, manage changes and retrieve evidence when needed.

A streamlined process is useful. Missing technical evidence is not.

Can Installers Outsource Heat Pump Design Under MCS:2025?

Installation businesses can use external technical specialists within appropriately managed arrangements, subject to the applicable scheme requirements.

Outsourcing might involve a complete heat-pump design or selected parts of the process, such as room-by-room heat loss, emitter assessment, hydraulic calculations or independent technical review.

However, commissioning an external designer doesn’t automatically transfer MCS certification or installation responsibility to that designer.

The certified installer must maintain appropriate oversight of the project.

Clear arrangements should establish:

Who collects and verifies property information.
Which calculations and design tasks are outsourced.
What standards and design assumptions apply.
Which documents the external designer will deliver.
How technical questions and revisions are handled.
Who reviews and approves the design for installation.
How changes on site are incorporated into the final records.

This is especially important when an installation changes after the initial design has been issued.

For example, replacing the specified heat pump or reducing a radiator size may require further calculations before the altered installation can be accepted.

At Heat Loss Hub, we provide agreed technical design support to installers working under their own certification.

For a fuller explanation, read Can Heat Pump Installers Outsource System Design?

MCS:2025 Transition Checklist for Heat Pump Installers

If your business hasn’t yet completed the transition, the following checklist provides a useful starting point.

Item	What to check
Certification	Are we certified under the previous scheme or MCS:2025?
Transition	What has our certification body confirmed?
Technical Supervisor	Do we have appropriately competent and qualified supervisors?
Technical standards	Are we using the applicable design and installation editions?
Consumer protection	Which consumer-code and Customer Commitment requirements apply?
Financial protection	Have the required arrangements been established?
Operating scenario	Do our processes match the nature and complexity of our business?
Project documentation	Can we retrieve designs, records and revisions?
External designers	Are technical responsibilities and approvals clear?
Assessments	Can we demonstrate competent design and installation delivery?

Practical Steps to Take Now

First, establish your current certification status and review communications from your certification body.

Next, check the relevant MCS scheme documents, Technical Supervisor competence and business operating requirements.

Review the way your company prepares quotations, collects surveys, produces designs, manages installation changes and stores project records.

Where external designers or subcontractors contribute to projects, ensure responsibilities and working arrangements are documented.

Finally, identify anything that could prevent the business from demonstrating compliance during certification-body assessment.

This is a preparation checklist, not an official certification assessment or a substitute for your certification body’s requirements. The latest MCS scheme documents and transition guidance should always take precedence over a general industry article.

What Do the MCS Changes Mean for Homeowners?

For homeowners, MCS certification remains important when selecting an installer and considering government-funded heat-pump work.

In England and Wales, the Boiler Upgrade Scheme continues to require an appropriately MCS-certified installer.

The redeveloped scheme introduces changes to consumer protection and installer accountability, but it doesn’t mean that every certified business has already transitioned.

A homeowner can ask an installer which scheme they currently operate under, what consumer protections apply and who is responsible for technical supervision.

It’s also reasonable to request the room-by-room heat loss calculation, proposed heating temperatures, radiator assessment and justification for the selected heat pump.

Certification supports recognised standards, but it doesn’t remove the value of checking whether a particular design is appropriate for the property.

Homeowners with concerns about proposed systems can explore Independent Heat Pump Design Reviews.

Frequently Asked Questions About MCS Changes

When must existing installers transition to MCS:2025?

MCS’s published phased transition runs from February 2026 to 31 March 2027. Individual installers should follow their certification body’s arrangements and continue complying with the previous scheme until their transition is formally completed.

Is RECC or HIES membership still required?

Under the previous MCS scheme, approved consumer-code membership remains required. Under the redeveloped MCS:2025 scheme, separate membership is no longer mandatory. Businesses should check their certification and BUS obligations before cancelling membership.

Does every installation need a Technical Supervisor?

Under MCS:2025, each registered installation requires an assigned Technical Supervisor who meets the applicable competency requirements and takes responsibility for its technical compliance under the scheme. The installer also needs suitable supervision arrangements for the way the business operates.

Which MIS 3005 design standard applies?

That depends on the scheme and applicable project requirements. The September 2026 BUS notice lists MIS 3005-D Version 3.0 and MIS 3005-D:2025 Version 2.0 among the approved documents. Installers should confirm the appropriate edition rather than assume the documents are interchangeable.

Can installers outsource heat loss calculations and system design?

Yes, external design support can form part of an appropriately managed installer workflow. However, the certified installer must retain and discharge its applicable responsibilities for certification and the completed installation. Technical scopes, design assumptions, reviews and changes should be clearly documented.

CONTENTS

STANDARDS ARE OUR LOVE LANGUAGE

Our design packs are built to the documentation standard MCS installers need — whatever version of the rulebook applies.

INDEPENDENT DESIGN SUPPORT FOR MCS INSTALLERS

Changes to MCS certification don't reduce the need for accurate heat loss calculations and clear technical records

Heat Loss Hub provides independent heating-design support for installers who need additional technical capacity — room-by-room heat loss calculations, radiator and emitter design, heat-pump selection, hydraulic assessment, hot-water design, documentation and technical review, depending on the agreed scope. We support individual difficult projects, temporary design overflow or regular outsourced design work. Your business retains its certification, customer relationships and installation responsibilities — we provide the technical work agreed for the project.