What’s New in MCS-020(a)? A Deep Dive into Sound Calculations for Heat Pumps

What’s New in MCS-020(a)? A Deep Dive into Sound Calculations for Heat Pumps

Over the past few months, the Microgeneration Certification Scheme (MCS) has rolled out significant updates to the way sound is measured and managed for heat pump installations, especially under the updated MCS-020(a) standard. If you’re an installer, homeowner, or AV enthusiast, it’s crucial to understand these changes—and how they shape noise compliance, acoustic design, and planning permissions. Let’s dive into the sound calculations.

1. Lowering the Noise Threshold: From 42 dB to 37 dB

One of the headline shifts is the reduction in the maximum allowable noise limit for neighbour-sensitive installations—down from 42 dB to 37 dB LAeq, 5‑minute measurements. That difference may seem small, but in decibel terms, it translates to more than a halving of perceived sound energy. In quieter neighbourhoods, this stricter bar forces installers to revaluate system placement, shielding, and equipment selection.

2. From Sound Pressure to Sound Power

Historically, MCS noise assessments focused on sound pressure—as measured at a neighbour’s window. Now, heat pump noise is evaluated based on sound power level—essentially the machine’s inherent output. This shift empowers installers to account for factors like fan noise and compressor operations without the complications of onsite ambient variations. As a result, the emphasis moves toward robust acoustic modelling and proactive design. MCS-020 sound calculations can all be provided by Apex Renewable Surveys.

3. Accounting for Multiple Units

Another major step forward: the updated standard recognises that noise from multiple units doesn’t simply add linearly. Instead, there's cumulative impact, requiring more careful planning when clustering heat pump units—common in apartment blocks or multi-home developments. The new methodology adjusts calculations to include this nuance.

4. Clearer Guidance on Acoustic Barriers

MCS-020(a) now offers detailed guidance on the effectiveness of acoustic barriers (fences, walls, enclosures). These are no longer vague add-ons; they're essential components with defined reduction values. That means installers can—and should—design wrongfully placed or underspecified barriers at their peril. This update encourages the use of targeted noise-reducing structures and early-consult acoustic advice.

5. Why the Changes?

These updates weren’t made lightly. They’re part of a broader movement to ensure heat pump deployment aligns both with decarbonisation goals and with maintaining neighbourhood harmony. Acoustic complaints, particularly in suburban and rural settings, spiked as installations increased, prompting feedback from acoustic consultants, councils, and residents. The revisions respond directly to concerns that the previous standard risked overlooking human-centric aspects of noise impact.

Practical Impacts for Installers & Designers

Equipment Selection

Installers now need heat pump units with lower sound power outputs, especially if using multiple units. Some manufacturers are stepping up by offering “quiet mode” or low‑noise versions tailored to these requirements. In some cases, equipment previously installed under 42 dB rules may no longer be compliant—prompting reviews of product specs at quote and specification stage.

Layout & Placement

Repositioning units becomes more critical. You may need to move units further from neighbours or elevate them away from ground-level proximity. In tight spaces—terraced homes and apartment blocks—planning the layout becomes more challenging, but essential when aiming for permits under permitted development rules.

Barrier Specification

Where previously a garden fence might have seemed adequate, it now must meet a defined attenuation specification. Some installers are opting for fencing with integrated acoustic core, bespoke baffles, or even pre-built enclosures. These solutions demand upfront design, cost, and guidance—far from the simple measures of the past.

Acoustic Modelling

With the move to sound power logic, a reliable acoustic model is vital. This shift towards prediction rather than measurement means installers should use validated noise modeling tools during system design. It’s no longer enough to tweak after the fact; compliant designs need to be planned.

Planning & Permitted Development

In England, recent changes to Permitted Development Rights were aligned with MCS updates. Now installations can be situated closer to boundary (- including within 1 metre), units can be bigger (up to 1.5 m³), and more units allowed on detached homes. However, all must comply with MCS-020(a), meaning close warranty and acoustic compliance go hand-in-hand. A site previously permissible might now trip on acoustic non-compliance, even if other PDR conditions are met.

Homeowner Perspective

More Comprehensive Surveys

When homeowners talk to installers, they should ask about how the MCS updates affect their specific property. Quieter days, sensitive neighbours, or partially enclosed gardens could require more detailed layouts, barriers, or quiet equipment.

Potential Cost Impacts

Improvements have a cost: better equipment, enclosures, or adjustments to placement can raise quote totals. That said, MCS updates allow installers to offer compliant, reliable systems upfront—eliminating delays and avoidable planning costs later.

Future-Proofing

By choosing systems and designs aligned with 37 dB and acoustic barrier guidance, homeowners gain peace of mind regarding future noise complaints or statutory nuisance issues. In short: a well‑executed compliant install offers more predictable neighbourhood outcomes.

Real‑World Example

Take a small terraced house. Under the old 42 dB rule, a standard 8 kW outdoor unit might pass at two metres from the neighbour’s bedroom window. Post‑update, the same unit fails, requiring relocation or acoustic enclosure. Add a second unit (as permitted for detached or larger homes), and cumulative noise tips the scales—necessitating barrier use or more distant siting. Installers are now including these design steps as standard, even where not legally enforced by a council.

FAQs

Q: When did these changes take effect? A: The new MCS-020(a) standard was issued in March 2025; installing under Permitted Development Rights with the updated rules is expected by late 2025, though guidance and adoption began earlier.

Q: Do these changes apply across the whole UK? A: England has updated Permitted Development rules to align with MCS-020(a). Scotland, Wales, and Northern Ireland remain under existing MCS-020 rules until further notice, but installers there are beginning to adopt the newer standard voluntarily to future-proof installs.

Q: If my system fails the new noise calculation, can I still install? A: Technically, yes—but only via full planning permission rather than permitted development. Councils may require statutory controls (e.g., BS4142 assessment), so compliant design is the simpler route.

Q: Will quieter equipment be more expensive? A: Possibly—but lots of manufacturers are bringing out low‑noise or quiet‑mode models to meet these standards. Often they're priced competitively, but barrier costs and siting adjustments may raise overall install price.

Tips for Installers & Designers

1. Engineers First, Installers Second Start every design focusing on acoustics: sound power specs, placement, barriers. Don’t treat acoustic modeling as an afterthought.

2. Use Early Acoustic Checks Include pre‑quote calculations using manufacturer sound power data to test compliance. If barriers or siting need adjustment, do it before committing.

3. Educate Clients Help homeowners understand why a bigger unit, barrier, or relocated site might cost more—but avoid future complaints and delays.

4. Barrier as Design Element Acoustic fences, baffles, or wall extensions should be specified like any other system component, with known attenuation properties.

5. Document Thoroughly MCS compliance means keeping all calculations, barrier specs, and acoustic modelling output in file. It helps with future inspections or neighbour complaints.

Conclusion

The MCS-020(a) update represents a thoughtful evolution in heat pump acoustic standards, aligning decarbonisation ambitions with community wellbeing. While the reduction to 37 dB, shift to sound power, and emphasis on cumulation and barriers raise the compliance bar, they also nudge the industry toward quality-first design.

Yes, these changes are more work for installers and designers—but they prevent conflict down the line. For homeowners, they offer reassurance that their investment will be quieter, more considerate, and more resilient to planning scrutiny.

By embedding acoustic rigor into projects from Day One, the UK heat pump market can scale up without sacrificing neighbour peace. As demand continues to grow, these updates will help ensure the wider renewable energy transition is as silent as it is sustainable.