Heat pump commissioning under BUS V5: a 2026 compliance playbook

BUS V5 came into force on 28 April 2026, and the new rules - mandatory upfront grant discount, expanded eligibility, tighter audit checks - all converge at the commissioning stage. Commissioning is also the part of a heat pump install that everyone assumes is under control, right up until a customer rings the office asking where their MCS certificate is, and nobody can answer. At that point the job is costing you time, goodwill, and sometimes a referral.

For UK heat pump installers running 15+ jobs a month, commissioning is also the single biggest compliance exposure. MIS 3005-D and MIS 3005-I, MCS Installation Database (MID) registration, BUS V5 voucher application and redemption, DNO notification via the ENA heat pump / EV form, Part L and Part F Building Regulations - they all converge in the days after the engineer leaves site. If that process is ad-hoc, it's a ticking time bomb.

What "commissioning and compliance" actually covers on a heat pump install

For a typical air-source heat pump install under the Boiler Upgrade Scheme, commissioning isn't one event - it's a cluster of obligations that all land at the end of the job:

Obligation	What it is	Who needs it
MIS 3005-I commissioning	Technical commissioning per MIS 3005-I (installation) against the MIS 3005-D design - system checks, flow rates, settings	MCS certification body
MCS design certificate	Proof the system was designed correctly (heat loss, emitter sizing, DHW sizing)	MCS / homeowner
MCS installation certificate	Proof the system was installed to design and commissioned correctly	MCS / homeowner
MID registration	Record on the MCS Installation Database proving the install happened	Ofgem / BUS
BUS V5 voucher application + redemption	Pre-install voucher application with upfront discount on quote/invoice; post-install voucher redemption	Ofgem BUS portal
ENA HP/EV notification	DNO notification of new heat pump load (Maximum Demand)	Local DNO
Part L / Part F compliance	Building Regulations sign-off	Building Control
Homeowner handover pack	Warranty, commissioning data, O&M, MCS cert copies	Customer

Miss any one of these and the consequences range from a delayed grant payment (painful) to loss of MCS accreditation (existential). The problem isn't that installers don't know they need to do it. It's that the data needed for every one of these documents lives in different places - some on paper, some in spreadsheets, some in the engineer's head.

Why commissioning goes wrong (even when installers are trying hard)

I've spent the last year working with UK heat pump installers scaling from 5 to 25+ jobs a month. The same pattern shows up every time:

• Engineer completes the install on site, moves to the next job
• Office waits for engineer to "send through the paperwork"
• Paperwork arrives in fragments - some photos on WhatsApp, some on email, some nothing
• Admin spends 2-4 hours chasing information and assembling the handover pack
• MCS certificate and MID registration happen days or weeks later
• BUS voucher redemption sits behind MID registration - so cash flow suffers
• Customer rings asking for their paperwork, generating rework

None of this is about laziness. It's what happens when the commissioning process is separate from the install itself - when the data lives in different places from the engineer who did the work. The fix isn't more discipline. It's a workflow where commissioning data is captured at the point of install and flows into every document that needs it.

The best heat pump installers I work with treat commissioning as part of the install, not a separate paperwork job. If your engineer is walking off site without the data captured, you're going to pay for it in the week that follows.

The MIS 3005 checklist: what has to be captured on site

MIS 3005 is the Microgeneration Installation Standard for heat pump design and installation in the UK. It was split on 1 April 2022 into two documents - MIS 3005-D (Design) and MIS 3005-I (Installation) - and the current versions are the 2025 issues of each. If anyone in your office is still working from a single pre-2022 "MCS 3005" document, that's the first thing to fix.

The key technical items that must be captured at commissioning:

• Flow and return temperatures at design conditions
• System flow rate (L/s or L/min) at commissioning
• Refrigerant circuit sign-off (F-Gas Category I/II qualified person, split installs only)
• Hot water cylinder performance and legionella pasteurisation cycle set
• Emitter sign-off (radiators or UFH - correct sizing verified on site)
• Weather compensation settings and commissioning data
• MCS 020 (a) sound assessment - install matches the design assumptions (Permitted Development requires ≤37 dB(A) at the MCS 020 (a) assessment position; standard updated September 2025)
• Electrical isolation, RCD, and earth bonding verified
• Pressure test and water quality sample recorded
• Homeowner handover - system operation, temperatures, controls, MCS documentation explained

Every item above has to be captured on site. If the engineer leaves without capturing any of them, the office can't produce a clean commissioning certificate. The typical rework cost per missed item is a phone call, an email, or in the worst case, a return site visit.

The MCS Installation Database (MID): what it is and why it matters

The MID is the central record of every MCS-certified microgeneration install in the UK. Every heat pump you certify under MCS has to be registered on it within 10 working days of commissioning.

The data you need for MID registration:

• Installer and MCS certification number
• Customer details and install address
• Property type and build year
• Technology (air-source, ground-source), model, output (kW)
• Heat loss calculation result
• Design SPF (Seasonal Performance Factor)
• Emitter system (radiators, UFH, mix)
• Commissioning date and engineer

All of this should exist in your survey, design, and commissioning records already. The problem is getting it into the MID portal without re-keying. Installers running this smoothly have these fields captured once, in the same system, and simply submit to MID rather than typing it all over again.

Two reasons MID registration matters:

1. BUS voucher redemption is blocked until MID is registered. No MID certificate, no redemption approved, no grant paid. That's cash flow - and under V5 it's your working capital, not the customer's.
2. MCS audits spot-check MID entries. A pattern of late, incomplete, or missing MID records is what triggers an audit escalation. That's existential.

BUS V5: from install to cash under the new rules

The Boiler Upgrade Scheme moved to Version 5 on 28 April 2026 under the Boiler Upgrade Scheme (England and Wales) (Amendment) Regulations 2026 (SI 2026/390), made on 19 March 2026 and in force from today. The scheme has been extended to 2030, and the 2026/27 budget was increased to £400 million (up from £295m the previous year), approved 1 April 2026. The voucher mechanism itself is unchanged - vouchers are still applied for, issued, and redeemed via the Ofgem BUS portal. What V5 layers on top is a new, mandatory upfront discount: the installer must pass the grant value on as a discount on the customer's quote and invoice, and must not request or accept the discounted amount from the property owner (V5 Installer Guidance, para 2.03).

V5 grant amounts:

• £7,500 - air-source or ground-source heat pump, rising to £9,000 where the off-grid oil and LPG uplift applies (see below)
• £2,500 - air-to-air heat pump (newly eligible under V5, residential properties only, and excluded from the uplift)
• Exhaust air heat pumps that deliver heat via liquid are now eligible for the £7,500 ASHP grant

V5 also tightens the technical eligibility:

• The heat pump system must have sufficient kilowatt thermal capacity to provide 100% of the property's space heating needs
• Multi-heat pump (cascade) systems are capped at 70 kWth total
• Shared ground loop systems are capped at 300 kWth total, with each connected heat pump ≤45 kWth
• Non-fossil-fuel supplementary heating appliances (storage heaters, heat batteries, immersion) are now explicitly allowed alongside the BUS-funded heat pump

The practical V5 install-to-cash sequence (regulatory requirements applied to a real-world sales motion):

1. Eligibility pre-checked at survey - property type, existing heating system. Photos of the existing heating system are now required in all cases under V5 (not only where an EPC is missing). Where no valid EPC exists, the property owner provides alternative evidence: a recent utility bill or fuel receipt, photographs of the existing heating system, and an expired EPC if available.
2. Installer issues the quote showing total cost, BUS grant amount as an upfront discount, and net amount payable - the deduction is conditional on Ofgem approval, and your T&Cs need to spell out who carries the risk if the application is later rejected.
3. Customer accepts the conditional quote and pays a deposit on the net amount.
4. Installer submits the BUS voucher application on the property owner's behalf - typically once the customer has committed and signed the contract, since the application captures the customer's details and consents.
5. Ofgem approves and issues the voucher (this often happens while the install is being scheduled or in progress).
6. Install completed and commissioned to MIS 3005-I.
7. MID registered within 10 working days of commissioning.
8. Installer redeems the voucher via the Ofgem BUS portal, referencing the MID certificate.
9. Property owner confirms receipt of the upfront discount as part of the redemption checks (V5, para 2.05).
10. Ofgem reviews and approves the redemption.
11. Payment released on the next scheduled weekly payment day - typically 10-15 business days from approval.

The installer-controlled parts of this chain are steps 1-4 (pre-install) and 7-8 (post-install). At best, a tight operation gets from install-complete to voucher redemption submitted in 48 hours. At worst, installers sit on completed jobs for 2-3 weeks before redeeming - usually because the MID paperwork wasn't ready.

Cash flow shape under V5 is similar to what most V4 installers were already running - but it's now mandatory rather than a commercial choice. Under V4 you had the option: deduct the voucher value from the customer's quote and carry the working capital gap yourself (what most installers did to make the price visible to the customer), or quote the full price and let the customer absorb the gap until the voucher was redeemed (rarer, customer drop-off risk). V5 removes that choice. The grant must be shown as an upfront discount, the customer pays net, and the installer cannot ask them to pay the discounted amount. Submission speed was already cash-flow-important for any installer who quoted net under V4; under V5 it's important for everyone, by regulation.

At 20 installs a month, a month of unredeemed vouchers parks £150k of grant income with Ofgem instead of in your bank account. Fixing commissioning speed is often the single highest-impact operational change a heat pump installer can make.

DNO notification: the ENA heat pump / EV form

Heat pumps are electrical loads, not generators - so the notification route is the Energy Networks Association (ENA) Single EV Charge Point and Heat Pump Installation Application Form, not G98/G99. (G98 and G99 are the engineering recommendations for generation - solar PV, batteries, V2G - and only come into play if the property also has generation kit on the same connection.)

The notification is triggered by the new Maximum Demand (MD) the install creates on the property's supply, not by the heat pump rating in isolation:

• New MD ≤ 60A per phase - install can proceed; notify the DNO within 28 days of install
• New MD > 60A per phase - apply to the DNO before install and wait for approval before connecting

For a typical 5-12 kW domestic ASHP on a single-phase supply, the heat pump's design current is in the 5-15A range (with higher peaks during defrost or backup heater operation). But the MD calculation is the combined load of the heat pump plus the rest of the property's existing demand - that's what determines which side of the 60A threshold you fall on. On older properties with electric showers, electric ovens, or an EV charger already installed, the heat pump tips the property over the threshold more often than installers expect.

Miss the post-install notification and it's a compliance issue that shows up on audit. Start an install that needed pre-approval without it, and the DNO can require the system disconnected until approval is in place - genuinely bad for you and the customer.

The practical fix is the same as MCS: capture the electrical data and existing loads once at survey, calculate the new MD, flag pre-approval cases for the DNO before install, and automate the post-install notification as a step in the commissioning workflow.

Homeowner handover: the last 30 minutes that save you weeks of rework

The handover on site is where most installers stop paying attention. It's also where a third of customer service calls originate. A structured handover covers:

• System walkthrough - how to operate, set temperatures, schedule
• Weather compensation - what it is and why they shouldn't turn it off
• Thermostat and controls training
• DHW operation and cylinder setpoints
• Noise, defrost cycles, and normal sounds they'll hear
• Warranty activation and how to claim
• Service schedule and legionella pasteurisation cycle
• Handover pack explained - MCS cert, commissioning data, O&M manual, warranty docs

Thirty minutes on site here prevents an average of 3-4 customer calls in the first month post-install. On 20 installs a month that's 60-80 calls that don't need to happen - which is a full day a week of office time saved.

The systemised commissioning workflow: what "good" looks like

Here's what I see across the heat pump installers running 25+ installs a month with clean compliance:

1. Survey captures everything upstream. Heat loss, emitter check, electrical info, new MD calculation, DHW demand, photos of the existing heating system (now mandatory under V5), and EPC or alternative evidence pack (utility bill or fuel receipt, expired EPC where available) - all captured on mobile during the technical survey, not re-gathered later.
2. Design lives with the survey. MCS design certificate generated from survey data. No re-keying.
3. Quote shows the BUS grant as an upfront discount from the start. Total cost, grant deduction, net payable - all generated from the survey data, and the deduction is shown as conditional on Ofgem approval. The formal voucher application goes in once the customer signs the contract.
4. Engineer has the full job on mobile on site. Design, kit list, customer notes, installation instructions - all in one place. Commissioning checklist is part of the same record.
5. Commissioning data captured as the engineer works. Flow temps, MCS 020 (a) sound assessment reference, photos, homeowner signatures - all go in as the engineer completes each step.
6. Handover pack auto-generated. MCS commissioning cert, MID data, O&M manual, warranty docs assembled from the captured data and emailed to the customer before the engineer leaves site. Property owner confirms receipt of the upfront discount.
7. MID registered within 48 hours. Admin simply reviews and submits - no data entry.
8. BUS voucher redemption submitted within 48 hours of MID registration. The redemption goes in as soon as MID is in place.

The end-to-end difference between this and the WhatsApp-and-email version is roughly:

• 3-4 hours of admin saved per job
• Zero return visits for paperwork
• Customer handover pack in their inbox same day
• BUS voucher redemption submitted sooner after commissioning, because the data is already captured
• Clean MCS audit trail if you're ever spot-checked

How Payaca supports heat pump commissioning

Payaca isn't a "BUS V5 widget" - it's a flexible platform you configure for the workflow you need. For UK heat pump installers running this tightly, that means using custom fields and HTML document templates to model the MCS, MID, and BUS V5 requirements end-to-end, plus direct integrations where they save real time.

• Custom fields you configure for MIS 3005, MID, and BUS V5. Build out the survey, design, install, and commissioning checklists to capture exactly the data each requirement needs. Required fields are enforced on site so engineers can't sign off without them. Photos, signatures, dropdowns, and structured data are first-class field types - including the V5 photos of the existing heating system and the alternative-evidence pack where there's no EPC. Whatever the engineer captures in the field flows straight back to the office record.
• HTML document templates that auto-generate from the captured fields. Configure templates for the customer quote, invoice, MCS commissioning certificate, MID export, and homeowner handover pack - all drawn from the same data set, no re-keying. Quote and invoice templates are configurable to show the BUS grant as an upfront discount with total / grant / net payable, structured to be V5-audit-ready (V5 para 8.09).
• Direct integrations for the slow bits. EPC data is pulled directly into the survey rather than re-typed; DNO notifications are generated and submitted automatically via the integration rather than chased.
• Client portal handover. The homeowner pack is shared via a branded client portal where the customer can review documents, sign where required, and confirm receipt of the upfront discount as part of the V5 redemption checks.

The shape of the platform - flexible fields, configurable documents, direct integrations, client portal - is what lets you systemise heat pump commissioning without a year of bespoke development. Heat pump installers running Payaca this way get from commissioning to BUS voucher redemption faster, and spend less time on admin per job.

And because the platform shape doesn't change with the technology, the same configuration approach handles solar, battery, and EV charger jobs alongside heat pumps. One system across whatever mix of clean tech you install - so the operational discipline you build for heat pump commissioning compounds across the rest of the business.

What to audit in your own commissioning process this week

If you want to know how exposed you are, ask these six questions about last month's jobs:

1. What was the average time from install complete to MID registered? If it's more than 5 working days, you're holding cash and risking audit flags.
2. How many jobs this month had handover packs emailed to the customer within 24 hours of install? If it's under 80%, your customer experience is patchy.
3. How many return site visits were required after the engineer left? Every one costs £200-£400 of unbilled labour.
4. How many MID entries in the last 3 months had to be edited or corrected? Every correction is a sign the data capture upstream is weak.
5. What's your average time from install to BUS voucher redemption submitted? If it's more than a week under V5, you're carrying working capital you don't need to.
6. Are your post-28-April quotes and invoices V5-audit-ready? Each one needs to show total cost, BUS grant amount as an upfront discount, and net amount payable. V5 introduces Ofgem audit checks on grant deduction compliance (para 8.09) - any gap is a finding waiting to happen.

If any of these numbers are worse than you're comfortable with, the problem isn't willpower or engineer effort - it's workflow. Installers running this tightly aren't smarter; they've systemised the process so good practice is the default, not the exception. Less admin per job, BUS voucher redemption submitted sooner after commissioning, MCS accreditation protected - and you didn't have to add headcount to get there.

Related reading: Heat pump installer solutions | Heat pump installer economics: what actually drives margin | The Warm Homes Plan: what installers need to know | Mobile app for field teams