If you install heat pumps, 2025 has been one of the busiest years for regulatory change in the history of the trade. A completely rewritten MCS scheme, new sizing standards, a government market mechanism that pays you per installation, and relaxed planning rules have all landed within months of each other.
We’ve broken it all down into what’s actually changed, when it took effect, and what you need to do about it.
MCS:2025: The New Certification Scheme
The Microgeneration Certification Scheme has been completely rewritten. MCS:2025 replaces the previous standards framework with a single, unified scheme that covers all small-scale renewable technologies.
If you hold MCS certification for heat pump installation, you’re already working under the new scheme. If you’re applying for the first time, the requirements have changed significantly.
What’s changed?
The old patchwork of separate MCS standards has been consolidated into one scheme document. Clearer structure, less duplication, easier to follow.
Stronger consumer protection requirements including pre-installation information packs, clearer performance estimates, and standardised handover documentation.
New quality management system requirements for installation businesses. You need documented procedures for design, installation, commissioning, and complaint handling.
Updated competence requirements for individual installers. The Named Technical Person role has been clarified with specific training and experience criteria.
If you’re already MCS-certified, review the transition guidance on the MCS website. Your certification body will audit you against MCS:2025 at your next surveillance visit. If you’re applying fresh, use the new application process which launched alongside the standard.
MIS 3005 Split: New Heat Pump Sizing Standards
The old MIS 3005 heat pump standard has been split into separate documents for different heat pump types. This is one of the biggest technical changes in years, and it directly affects how you size and design every installation.
The new structure
- MIS 3005-D — Design standard (covers heat loss calculations, sizing, and system design for all heat pump types)
- MIS 3005-I — Installation standard (covers commissioning, testing, and handover for all heat pump types)
Each document now contains technology-specific sizing methodologies, design requirements, and commissioning procedures. The old one-size-fits-all approach to heat loss calculations and system design is gone.
If you’re still using the old MIS 3005 spreadsheet for heat loss calculations, stop. The new standards require technology-specific sizing tools, and your MCS certification body will check this at audit. Make sure your design software is updated to the current standard before your next installation.
What this means in practice
For most installers doing domestic air source work, MIS 3005-D covers design (heat loss calculations, flow temperature, sizing) and MIS 3005-I covers installation (commissioning checklists, testing, handover) for all heat pump types. Read both cover to cover before your next installation.
Clean Heat Market Mechanism: Getting Paid Per Install
The Clean Heat Market Mechanism (CHMM) is a manufacturer obligation scheme that requires boiler manufacturers to sell a proportion of heat pumps alongside their boiler sales. Manufacturers who fall short can buy “credits” from heat pump installers who exceed their targets. Note: the domestic Renewable Heat Incentive (RHI) was replaced by the Boiler Upgrade Scheme (BUS), which pays grants directly to homeowners. The CHMM is a separate supply-side mechanism and is not a replacement for the RHI.
Why this matters to you
Every MCS-certified heat pump installation generates a credit. These credits have a market value, and manufacturers are already buying them. As an MCS-certified installer, each qualifying installation you complete is worth money beyond the installation fee itself.
The practical upshot: heat pump installations are now financially incentivised from both the demand side (the Boiler Upgrade Scheme grant to the homeowner) and the supply side (CHMM credits to manufacturers who need them). This is driving significant growth in the market.
Credits are generated automatically when you log a qualifying installation through MCS. You don’t need to do anything extra beyond completing your normal MCS documentation and MCS installation certificate. Your certification body handles the credit registration.
Planning Rule Changes: Permitted Development Expanded
The Government has expanded permitted development rights for heat pumps in England. Previously, domestic air source heat pumps had to meet strict noise and distance requirements that made installation difficult on terraced houses and smaller properties. The May 2025 changes relax several of these restrictions.
Key changes
- Noise limits updated to reflect modern, quieter heat pump models. The old 42dB limit at the nearest neighbour’s window was based on older, louder units.
- Distance-from-boundary rules relaxed for smaller units, making terraced and semi-detached properties much more viable.
- Flat roof installations now permitted under specific conditions, opening up options for properties where ground-level space is limited.
- Listed buildings and conservation areas still require planning permission, but the guidance has been clarified to reduce unnecessary refusals.
For installers, this means fewer projects stalling at the planning stage. Properties that were previously unviable due to planning constraints are now potential installations.
Boiler Upgrade Scheme: Still Running, Bigger Grants
The Boiler Upgrade Scheme (BUS) continues to offer grants for homeowners replacing fossil fuel heating with heat pumps. The grant for air source and ground source heat pumps is £7,500, up from the original £5,000. Biomass boilers in rural properties are eligible for £5,000. The scheme has been extended to March 2028, giving the market long-term certainty.
As an installer, the BUS grant is your single best selling tool. A £7,500 reduction in the upfront cost makes the conversation with homeowners significantly easier. You apply for the grant on behalf of the customer through the MCS portal once the installation is complete and your MCS certificate is lodged.
Combined with the CHMM credits, the economics of heat pump installation have never been stronger. A typical domestic ASHP installation that might have been a hard sell two years ago is now backed by £7,500 in grant money plus credit income.
Key Dates at a Glance
| Date | What | Impact |
|---|---|---|
| 1 Apr 2025 | Clean Heat Market Mechanism in force | MCS installs generate tradeable credits |
| May 2025 | Permitted development rules expanded | More properties eligible without planning |
| 1 Jun 2025 | MCS:2025 live | New unified certification scheme |
| 1 Jun 2025 | MIS 3005 split into A/G/W/E | Technology-specific sizing standards |
| Apr 2025 | BUS grant increased to £7,500 | Bigger customer incentive |
| Mar 2028 | BUS scheme end date | Grants guaranteed until then |
| 2026 | Future Homes Standard takes effect | No gas boilers in new builds |
The Practical Takeaway: Four Things to Do Now
The regulatory landscape has shifted firmly in favour of heat pump installers. But only if you’re set up to take advantage of it. Here are the four things to sort out now.
- Get your MCS:2025 house in order. Review the transition guidance, update your quality management documentation, and make sure your Named Technical Person meets the new competence criteria. Your next surveillance audit will be against the new standard.
- Update your sizing tools. If you’re installing air source heat pumps, MIS 3005-D (Design) and MIS 3005-I (Installation) are your bible. Ditch the old single MIS 3005 document and make sure your design software complies with both current standards. Wrong sizing is the single biggest cause of MCS non-conformances.
- Understand the money. Between BUS grants (£7,500), CHMM credits, and the growing demand from the Future Homes Standard, the business case for heat pump work has never been stronger. Make sure you’re claiming everything you’re entitled to.
- Keep your documentation tight. MCS:2025 has stronger requirements for pre-installation information, design records, commissioning data, and handover documentation. Digital tools that structure your certificates properly save time and reduce audit risk. CertBox supports MCS heat pump certificates, F-gas commissioning records, and air conditioning commissioning reports.
The Direction of Travel Is Clear
Heat pumps are no longer a niche product for eco-enthusiasts. With the Future Homes Standard banning gas boilers in new builds from 2026, permitted development making retrofits easier, and genuine financial incentives on both sides of the transaction, this is now mainstream heating work.
The installers who are already MCS-certified, up to date with the new standards, and running efficient documentation processes are the ones picking up the best work. The rest are still trying to figure out what MIS 3005-D and MIS 3005-I mean.
Don’t be the rest.
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Published February 2026. This article is for general guidance only and does not constitute legal or professional advice. Always refer to the full published standard and consult your MCS certification body for definitive requirements.