Survey, Procurement, G98, and Handover Discipline for Residential Solar PV Installers

The UK residential solar market is moving at a pace not seen for more than a decade. Government data from the Department for Energy Security and Net Zero (DESNZ) recorded 27,607 solar installations in March 2026 - the highest monthly volume since 2012 - with residential jobs accounting for 66% of all MCS-registered installs in volume terms that month. For a solar PV installer running 10 or 15 residential jobs per month, the operational picture is demanding: surveys, equipment orders, scaffold bookings, and DNO notifications all running in parallel, across jobs at different stages. The margin available on a standard residential install is limited. A 4 kWp system leaves little room for survey-to-procurement errors, missed G98 notification deadlines, or handover paperwork that sits unfinished and stalls the final invoice.

This resource sets out the four disciplines that separate residential solar PV businesses that grow profitably from those that grow busily: survey accuracy and DNO route confirmation, equipment procurement against confirmed jobs, commissioning documentation and the 28-day G98 window, and handover completion including MCS certificate issue and SEG registration support for the customer.

Survey Accuracy and DNO Route Confirmation

Every residential install starts with a survey. Most of the cost errors that appear later in the job were set during this visit - or in the design work immediately after it.

The first thing a surveyor must confirm is DNO route: G98 or G99. This is determined by the inverter AC output in amps per phase, not by the DC panel rating or kilowatt peak figure on the quote. A single-phase residential system with an inverter AC output up to 16A per phase - approximately 3.68 kW - qualifies for G98. This is the connect-and-notify route: the installer commissions the system, energises it, and then notifies the DNO within 28 days. No pre-approval, no application fee, no waiting before installation can begin. Above 16A per phase, the system moves to G99, which requires DNO approval before the installation starts. Discovering at commissioning that a system designed as G98 is in fact G99 - most commonly because battery storage was added to a system already close to the threshold - loses weeks the installation programme did not allow for and leaves a customer without a working system while the DNO application is processed.

Shading analysis is the second area where survey discipline matters most. Shade from chimneys, dormer windows, neighbouring roof lines, or trees can materially affect output and string design. A survey conducted in the wrong season or at the wrong time of day misses shade that will be present for several hours each day in winter. A surveyor who does not record the shading evidence with enough precision creates a design that neither the estimator nor the customer can later interrogate. When output underperforms the projection and the customer calls, the survey record is the only document that shows whether the issue was always in the design or arose from an installation defect.

Panel count, inverter selection, and string configuration must all be fixed at survey stage and treated as the baseline specification. Changes between survey and procurement - adding a panel, swapping to a different inverter model, adjusting string groupings - each carry the risk of pushing the system across the G98/G99 boundary, substituting a product that is not on the MCS Product Directory, or changing a delivery lead time that was already confirmed. Locking the specification at survey and requiring a formal change process for any deviation is the discipline that keeps the downstream steps predictable.

Equipment Procurement and Scaffold Coordination

Residential solar jobs have a tight cost structure. Equipment - panels, mounting systems, inverters, DC isolators, AC cabling, and switchgear - accounts for the majority of direct costs on a standard installation. The margin available is limited enough that a substitution forced by a stock shortage, or an expedited freight charge to meet an installation date, removes most of what the job was priced to return.

The discipline issue is almost never price at the point of ordering. It is timing. Procurement should happen against a confirmed job - a signed contract with a scheduled installation date and a locked specification - not against a forecast of how busy the coming month looks. Ordering ahead of confirmation ties up working capital across multiple jobs simultaneously and creates a materials position that does not match the live job schedule. Ordering late, after the customer has been given a date, means either calling the customer to push the date back or paying to get materials faster.

Scaffold has the same timing problem with less flexibility, because scaffolding cannot be ordered on short notice the way an inverter can be expedited. Scaffold must be erected by a crew at a specific address on a specific date. A scaffold erected three days before the installation crew arrives costs standing time at daily hire rates. A scaffold that is not ready when the crew arrives costs a rebooking. Lead times for residential scaffold in many UK regions stretch to two to four weeks during peak installation periods between spring and autumn. Confirming the scaffold date at the same time as the installation date - and against the same confirmed contract - is the only reliable approach.

Commissioning Documentation and the 28-Day G98 Window

For G98 installations, the 28-day notification clock starts at commissioning - the moment the system is energised. The notification is submitted by the installer through the relevant DNO's online connection portal. Once lodged, the DNO acknowledges receipt within five working days and processes the notification within four to eight weeks. There is no pre-approval, no fee, and no waiting period before the system can generate. The consequence of a missed 28-day window is not an immediate formal penalty, but an unnotified system cannot support the customer's application for the Smart Export Guarantee. Until the retrospective notification is filed and processed, the customer cannot register for SEG payments - and they will raise this with the installer, not with the DNO.

The documentation included in the G98 notification is largely the same information the customer needs in their handover pack and for their SEG application. A commissioning record that is incomplete - a missing protection settings value, an incorrect MPAN, an inverter model reference that does not match the current Energy Networks Association type-test register entry - stalls the notification, stalls the MCS certificate, and stalls the final invoice. The most consistent failure point is not that installers do not know what is required. It is that the information is not captured at commissioning, on site, before the crew leaves the property.

The minimum commissioning record for a G98 residential install covers: inverter make, model, and AC output in amps per phase; the type-test certificate reference for that exact model and issue; the commissioning date; protection settings as measured and confirmed; a single line diagram as installed; the MPAN the system sits behind; and the customer's full address. The Electrical Installation Certificate (EIC) covering the AC and DC work to BS 7671 is a separate document but carries the same handover obligation.

Building a commissioning checklist that makes every one of these fields mandatory - and does not allow the job to progress to the G98 notification stage until each field is confirmed - is the operational discipline that keeps notifications within the 28-day window across a pipeline of 10 or 15 concurrent jobs.

MCS Certificate Issue, Handover Pack, and SEG Registration

The MCS certificate is issued after the installation is registered with the MCS database following commissioning. For the customer, it is the key document for SEG registration with their energy supplier. SEG export tariffs among UK suppliers ranged from approximately 4p to 12p per kWh as at July 2026, varying by supplier and tariff structure. A household that installed solar panels expecting to export surplus electricity but cannot register because the MCS certificate has not arrived is a household that will call the installer repeatedly, leave a review, and tell their neighbours not to use the same company.

MCS certification applies to both the installation company and the products installed. An installer who specifies panels or inverters not listed on the MCS Product Directory creates a documentation problem that cannot be resolved at commissioning. It requires a product substitution that goes back to survey and procurement. The product eligibility check belongs at specification stage, before the purchase order is placed, not as a final check when the handover pack is being assembled.

The handover pack should contain: the MCS installation certificate; the Electrical Installation Certificate (EIC) to BS 7671; the G98 notification acknowledgement from the DNO including its reference number (which the energy supplier will ask for at SEG registration); the inverter type-test certificate for the exact model installed; commissioning results including protection settings; the single line diagram as installed; manufacturer warranties for panels, inverter, and mounting system; and user instructions covering monitoring, isolation procedures, and service contact details.

An installer who completes this pack on the day of commissioning - or within 48 hours - can issue the final invoice at the same time. An installer who assembles the pack one, two, or three weeks later is sending a final invoice into a period where the customer has already moved on, the SEG registration conversation has not started, and the goodwill from a clean installation has been eroded by the wait.

Managing Multiple Residential Jobs Concurrently

The operational challenge for a growing residential solar business is not any single job. It is 12 or 15 jobs at different stages simultaneously. Survey records from three weeks ago need to be retrievable at the point of raising the purchase order. Scaffold bookings confirmed last week need to be visible against the installation calendar. G98 notifications from jobs commissioned 18 days ago need to be in the DNO portal before the 28-day window closes.

A job management system that tracks each residential install through its stages - survey complete, specification confirmed, procurement raised, scaffold booked, installation date set, commissioned, G98 notified, MCS certificate pending, handover pack issued, final invoice sent - gives the business a live view of where every job stands and what is at risk. Without that view, the jobs approaching a compliance deadline are invisible until someone calls to find out why the paperwork has not arrived.

The UK passed 2 million total solar installations in March 2026. Residential installs accounted for the majority of that volume. The installers building sustainable businesses in this market are not the ones with the most survey capacity - they are the ones with operational systems tight enough that growth does not dilute the margin or the handover quality that generates referrals.

How Zigaflow Supports Residential Solar PV Installer Operations

Zigaflow gives residential solar PV businesses a single system covering quotes, jobs, purchase orders, and invoices - with each job record linking every step from the initial survey note through to the final invoice. Purchase orders are raised directly against a job, with delivery tracked against the installation date. The jobs view shows all live installations by status, making it straightforward to see which jobs need commissioning documentation completed and which G98 notifications are approaching the 28-day window.

Invoices are linked to the job record, so the final invoice can be issued as soon as the handover pack is complete - without chasing information through emails or relying on a paper file from three weeks earlier. Zigaflow integrates with Xero, QuickBooks, and FreeAgent for accounting, keeping financial records aligned with each job without duplicate data entry.

For residential solar businesses running higher volumes, Zigaflow's project tracking provides visibility across the full job pipeline - from survey through to paid invoice - in one place.

Residential solar in 2026 is a volume market with a thin margin structure. The operational disciplines that protect that margin - survey accuracy, procurement against confirmed jobs, commissioning documentation completed on site, and handover packs issued within 48 hours of completion - are not complex. They are simply the disciplines that require a system to enforce them consistently across every job, not just the ones someone remembered to chase.