Four Operational Disciplines for Solar PV Installers: From DNO Application to MCS Handover

The UK solar installation market is growing faster than at any point since the original Feed-in Tariff era. MCS-certified installations hit 257,397 in 2025 - a 32% increase on the prior year and the highest annual total on record (Solar Weekly, 2026). That growth comes with intensifying competition: there are now over 5,250 MCS-certified contractors, with 718 new solar PV businesses certified in 2024 alone. More installers competing for the same customer base pushes lead costs up and puts margins under pressure. On a typical residential install, equipment accounts for roughly 45% of the project value, labour 30%, and logistics including scaffolding and administration the remaining 25% (Renewables Excellence, February 2026). With standard 4kW PV-only systems ranging from £5,500 to £7,000, there is limited room to absorb avoidable sub-contractor costs, delayed DNO approvals, or documentation errors that hold up final payment. The four operational disciplines below address the most common gaps that separate installers who protect their margin from those who give it away.

Confirm G98 or G99 Status Before Pricing, Not After Signing

Every grid-connected solar PV installation in the UK requires either a G98 notification or a G99 application, depending on system size and configuration. Most standard residential systems with a total inverter output at or below 3.68kW per phase fall under G98: the installer can proceed with the installation and submit notification to the Distribution Network Operator (DNO) within 28 days of commissioning. Systems above that threshold require a G99 application submitted to the DNO before installation can legally begin. G99 applications typically take 8 to 12 weeks, and in busy periods can extend to six months or more (GE Solutions UK, September 2025).

This distinction matters more today than it did two years ago. Battery storage is now a standard addition on many residential installs, with MCS-certified battery deployments surging from 4,965 in 2023 to approximately 59,000 in the first nine months of 2025 - a 122% year-on-year increase (Solar Weekly, 2026). A solar PV system that would be G98 on its own frequently triggers G99 once a battery is added, because the combined inverter output pushes above the 3.68kW per phase threshold. An installer who books a three-week install window assuming G98 and discovers the job is actually G99 faces a delay of two months or more before the installation can proceed.

The fix requires one step at survey stage: confirm the total inverter output in kW per phase, including battery storage, before the quote is issued. State the applicable route - G98 or G99 - in writing within the quote document. For G99 jobs, submit the DNO application as soon as the customer signs, not when the installation date approaches. Include a written clause in the customer order stating that the installation programme runs from the date of DNO approval, not from the order signing date.

Equipment Procurement: One PO Per Supplier Per Job, Mapped to the Install Window

A standard solar PV project involves procurement from at least three separate suppliers: panels, an inverter, and - increasingly - a battery unit. Each carries a different lead time. Panels from UK distributors typically arrive within three to six weeks of ordering. Inverters run two to four weeks for commonly stocked models. Battery units, where demand has grown sharply, can take four to eight weeks for preferred specifications. An installation programme can only be locked once all equipment is confirmed for delivery, which means procurement must start within days of the customer signing - not when the installation date is three weeks away.

One PO per supplier per job, with the job reference number on every PO, is the control mechanism. Raise POs for panels, inverter, battery, and mounting hardware within five working days of the signed customer order. Include the required delivery date on each PO, working backward from the planned installation date with at least three days' float built in. Obtain a written acknowledgment from each supplier with a confirmed delivery date, within three working days of the PO.

When equipment arrives, count every item against the delivery note before signing: panel count by model, inverter model and serial number, battery modules, mounting hardware. Do not sign the delivery note until the count is complete and any transit damage has been checked. Photograph and report any discrepancy or damage to the supplier in writing on the same day, before signing the delivery note.

Scaffolding Sub-Contractor Coordination: Written Booking, Clear Timing, and Job-Level Cost Capture

Scaffolding on a residential solar install costs between £600 and £1,200 on a standard pitched roof, with an additional £300 to £1,000 or more for slate roofs, higher elevations, or more complex access (Optimum Electrics, January 2026). That represents a significant portion of the logistics budget on jobs where total margins are already thin. Scaffolding is almost always sub-contracted, which means it needs the same treatment as any other sub-contractor engagement: a written booking confirmation, a PO, and cost capture attributed to the job record before the customer invoice is raised.

The timing of scaffolding relative to the install window creates two distinct risks. Scaffolding erected too early and left standing while equipment is delayed or a DNO approval is awaited accumulates daily hire charges that erode the job margin. Scaffolding arriving late means the install crew cannot access the roof, the booked installation date is lost, and the cost of rescheduling - and any idle crew time - falls on the installer.

Four practices address both risks. Issue a written booking confirmation per scaffolding contractor per job, stating the required erection date, the expected strip date, the job reference, and the agreed weekly or daily hire rate including any overhire charges. Raise one PO per scaffold contractor per job, with the PO number referenced in the booking confirmation, before the booking is confirmed. Build a two-day float between the confirmed scaffolding erection date and the planned installation crew start date. Match the scaffolding invoice against the PO when it arrives, attribute the cost to the job record, and confirm the full scaffolding cost is captured before raising the customer's final invoice.

MCS Documentation: Compile Progressively, Link the Certificate to Final Payment

The MCS installation certificate is the customer's proof that the system has been installed to recognised UK standards by a certified contractor. Without it, customers cannot register for Smart Export Guarantee (SEG) payments - the scheme through which energy suppliers compensate households for surplus electricity exported to the grid. For most customers, SEG registration is one of the primary financial reasons for choosing solar, which makes the MCS certificate one of the most commercially important deliverables an installer provides.

MCS certification documentation covers the system design sheet, the Electrical Installation Certificate (EIC), commissioning test results, DNO notification or approval reference, and a handover pack including warranties and operating instructions. Attempting to compile all of this at the end of the job from scattered site notes increases the risk of errors, delays the MCS portal submission, and delays the customer's ability to register for SEG payments. It also delays the final invoice where the MCS certificate is used as a payment trigger.

The more effective approach is to compile progressively. Complete the system design sheet at survey and include it with the signed customer order. Complete the EIC and commissioning test results on installation day, before the crew leaves site. Submit the G98 notification on the day of commissioning, or confirm that G99 approval is already in place before mobilizing. Assemble handover documentation during the job - collect warranties when equipment is ordered and confirm operating instructions are included with the delivery receipt. Submit the MCS certificate via the MCS portal on the day of commissioning or the following day. Raise the final payment invoice on the same day the MCS certificate is issued, with the certificate number included on the invoice.

How Zigaflow Supports Solar PV Installer Operations

Solar PV installers managing multiple active jobs simultaneously need a system that connects the survey, the supply chain, and the compliance documentation without relying on spreadsheets and separate email threads for each job.

Zigaflow gives each solar installation its own job record from the point of customer acceptance. Purchase orders for panels, inverters, batteries, and scaffolding are raised from the job record with the job reference built in, and delivery notes are matched against each PO when goods arrive. The eForms App captures commissioning test results and site sign-off on mobile, with data linked directly to the job record. Stage invoices are created against named milestones - equipment delivery, commissioning sign-off, and MCS certificate issuance - with each invoice linked to the job for full cost visibility at every stage. Accounting sync to Xero, QuickBooks, or FreeAgent keeps the numbers current without a separate data entry step.

For installers running several concurrent installs across different sites, Zigaflow's project tracking gives visibility of which jobs are awaiting DNO approval, which have equipment on order, and which are ready to invoice - without having to open each job individually.

The four disciplines above are operational habits, not systems investments. G98/G99 determination at survey, job-linked POs mapped to the install window, written scaffolding bookings with strip-timing control, and progressively compiled MCS documentation can all be adopted today. With the UK market growing at record pace and over 5,250 certified contractors competing for the same customer base, protecting profitability requires eliminating the avoidable costs and delays that arise when these disciplines are missing.