Commissioning is where heat pump jobs get signed off - and where margin and customer satisfaction most often leak. A practical playbook for growing UK installers on MIS 3005, the MCS Installation Database, BUS V5 voucher applications and redemption, and clean handover.
Matt Franklin
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.
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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.
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:
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.
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:
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.
Refrigeration sign-off
Split systems with field-made refrigerant connections need an F-Gas qualified person to do and sign off the refrigerant work, and that certification has to flow into the MCS commissioning certificate. Monobloc systems with sealed factory refrigerant circuits don't need separate F-Gas sign-off on site - the refrigerant work was done in the factory. For split installs, don't leave refrigeration sign-off as an afterthought - it's a common sticking point on MCS audits.
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:
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:
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:
V5 also tightens the technical eligibility:
The practical V5 install-to-cash sequence (regulatory requirements applied to a real-world sales motion):
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.
V5 changes if you've worked under V4
The voucher mechanism itself is unchanged - vouchers are still applied for, issued, and redeemed. The substantive workflow changes:
If your quoting and invoicing isn't already configured to show the grant as an upfront discount, that's the first template fix. Your admin team is also picking up a new reconciliation step on every BUS project, plus a survey-stage capture step for the heating system photos and alternative-evidence pack - worth standardising before volume builds. T&Cs are the third template to update.
Sources: SI 2026/390 - The Boiler Upgrade Scheme (England and Wales) (Amendment) Regulations 2026; Summary of Updates in the BUS Installer Guidance V5 (Ofgem); BUS Installer Guidance V5 (draft, March 2026). Note: the V5 Installer Guidance was published as a draft on 27 March 2026 and is the operative reference for V5 substantive requirements; Ofgem's "current" published guidance on its website may still link V4.2 until the V5 final replaces it.
Coming soon: £9,000 grant for oil and LPG households
Separate to V5, the government announced on 21 April 2026 an increase to the BUS grant for properties currently heated by oil or LPG, taking the total grant from £7,500 to £9,000. The announcement frames the uplift as targeted support for off-grid households facing rising fossil fuel costs - around 1.7 million homes in England and Wales fall into this category. The announcement doesn't itself commit to a commencement date; industry reporting points to July 2026 but Ofgem hasn't confirmed when applications will be assessed at the £9,000 level.
Practical implications for jobs in the pipeline:
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:
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.
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:
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.
Here's what I see across the heat pump installers running 25+ installs a month with clean compliance:
The end-to-end difference between this and the WhatsApp-and-email version is roughly:
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.
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 typically see the time from commissioning to BUS voucher redemption drop from 2-3 weeks to 48 hours, and save 2-4 hours of 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.
If you want to know how exposed you are, ask these six questions about last month's jobs:
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. Saved 2-4 hours of admin per job, BUS voucher redemption submitted within 48 hours of 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
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