UK Solar Design Software 2026: Best Tools for British Installers

The UK solar installation market in 2026 operates under a compliance framework that has no close parallel anywhere else in Europe. British installers must navigate MCS certification requirements, G98/G99 grid connection engineering recommendations, Distribution Network Operator notification procedures, Smart Export Guarantee rate calculations, and SAP assessment integration — all within a single project workflow. Each of those layers generates documentation. Most of that documentation is checked, audited, or submitted to external bodies.

The right solar design software does not just help with the roof layout. It automates the compliance stack that sits underneath every UK residential and commercial solar installation. Installers who rely on manual documentation processes spend six to eight hours per project on compliance paperwork alone. Platforms built for the British market compress that to under two hours — and reduce the audit risk that comes with manual compliance handling.

This guide reviews every major solar design platform against the specific demands of UK installers in 2026: MCS 012 string sizing compliance, G98/G99 validation, DNO notification pack generation, SAP calculation integration, and Smart Export Guarantee yield modelling. The goal is not a generic software ranking — it is a practical buying guide for British installers evaluating platforms against real workflow requirements.

In this guide:

• Latest 2026 updates — UK solar capacity, government targets, SEG rate movements, DNO processing times
• What UK solar installers specifically need from design software — MCS, G98/G99, SAP, DNO, SEG
• Full comparison table: SurgePV, Aurora Solar, PV*Sol, Helioscope, PVcase
• MCS certification and software documentation requirements in detail
• G98/G99 grid connection process and how software supports each stage
• SEG calculation methodology and export fraction modelling
• DNO application documentation — what each DNO expects
• How to choose by business size and project type
• Full FAQ: MCS, G98/G99, SEG, DNO, platform selection

Latest Updates: UK Solar Market 2026

The UK solar market entered 2026 in a materially different position from where it stood two years ago. Installed residential capacity surpassed 18 GW in late 2025. The government’s Contracts for Difference programme expanded support for subsidy-free solar, and battery storage installations are increasingly paired with new residential systems. The compliance environment has also shifted: MCS audits are more rigorous, DNO processing times have improved in some regions but remain unpredictable in others, and the SEG space has seen rate compression from larger licensees alongside rate increases from smaller, more competitive exporters.

The clearest operational trend is the widening gap between installers who have automated their compliance documentation and those who have not. In a market where MCS audits are more active and DNO submissions are increasingly digital, documentation errors that previously resulted in a correction letter now trigger formal audit procedures. Solar software that automates MCS-compliant documentation from the design itself — rather than assembling it manually after design completion — is no longer a competitive advantage; it is increasingly a baseline operational requirement.

The second major trend is battery storage integration. Most new UK residential systems include at least one battery unit, and the design software must handle the interaction between PV generation, battery charge/discharge cycles, grid export, and SEG calculation. Platforms that treat battery storage as an optional add-on module, requiring separate import and data re-entry, introduce errors at exactly the point where the financial model is most sensitive to accuracy.

What UK Solar Installers Need from Design Software

The UK compliance framework creates design software requirements that do not exist in the same form in any other market. Any platform you evaluate needs to handle all of the following as core functionality — not optional modules or manual workarounds.

MCS Certification and Documentation Requirements

MCS (Microgeneration Certification Scheme) certification is the primary quality standard for small-scale renewable energy installations in the UK. MCS certification governs both the installation company and the products used. For solar PV, the relevant standards are MCS 001 (installer certification), MCS 012 (product certification for PV modules and inverters), and the MCS Installation Standard for PV systems.

The MCS Installation Standard requires specific documentation for every certified installation:

• System design specification including module make/model, inverter make/model, mounting system, array configuration, and string design parameters
• String sizing calculations demonstrating compliance with MCS 012 string sizing methodology — specifically, that string voltage stays within inverter limits across the temperature range of the installation location
• Shading analysis and yield calculation using an approved irradiance dataset
• Installation checklist signed off against MCS installation standard requirements
• Commissioning record

Software that automates MCS-compliant string sizing calculations, generates the design specification from the completed design, and produces the shading analysis and yield report eliminates the most time-consuming elements of MCS documentation assembly. The string sizing calculation is particularly important: an MCS audit that identifies a string sizing error triggers a formal non-conformance that requires corrective action documentation and re-audit. Software-generated string sizing using the correct temperature-corrected voltage methodology eliminates this risk category.

G98/G99 Grid Connection Engineering Recommendations

The Energy Networks Association’s G98 and G99 engineering recommendations govern how distributed PV systems connect to the UK low-voltage and high-voltage distribution network. Understanding the distinction — and what each requires from design software — is fundamental to UK solar project workflows.

G98 applies to generating units with rated output up to 16A per phase. For a single-phase residential system, this means a maximum inverter AC output of approximately 3.68 kW. For a three-phase system, 16A per phase gives approximately 11 kW. G98 systems connect using a simplified registration process: the installer completes a G98 notification form and submits it to the relevant DNO. The DNO has 20 working days to object; if no objection is received, the system can proceed. In practice, most DNOs now process G98 notifications within 48–72 hours via digital submission portals.

G99 applies to generating units above the G98 threshold — typically commercial systems above 3.68 kW single-phase or 11 kW three-phase, and all systems with export above certain thresholds. G99 requires formal pre-approval from the DNO before the system can be installed and energised. The G99 process involves:

1. Stage 1 screening — installer submits basic system data; DNO determines if full study is required
2. Stage 2 (if required) — detailed power systems study to assess network impact
3. G99 acceptance letter — formal approval to proceed with installation and grid connection

G99 pre-approval timelines currently run 45–65 working days for standard commercial applications, longer for applications requiring Stage 2 studies. Design errors that cause a G99 resubmission add that full timeline again. Software that validates G98/G99 compliance in real time — flagging systems that cross the G98 threshold, checking export limitation settings, and generating the technical documentation required for G99 submission — prevents the resubmission cycle.

What software must handle:

• Real-time identification of G98 vs G99 threshold based on inverter rating and system configuration
• Automatic generation of G98 notification documentation in DNO-accepted format
• Generation of G99 application technical data — system specification, single-line diagram, inverter technical data, export limitation configuration
• Flagging of inverter export limitation settings required for G99 compliance
• Documentation of G99 Stage 1 submission data in the format expected by the relevant DNO

SAP (Standard Assessment Procedure) Calculations

SAP is the UK government’s method for assessing the energy performance of dwellings. For new-build properties, a SAP calculation is required to demonstrate compliance with Building Regulations Part L. For retrofit solar PV on existing properties, SAP integration is relevant where the installation supports an EPC (Energy Performance Certificate) or where the system is part of an energy efficiency package.

Design software integration with SAP affects UK installers in two primary ways:

New-build pipeline integration. Housebuilders and new-build contractors increasingly require solar PV as part of Part L compliance packages. SAP assessors calculate the required PV contribution to the dwelling’s energy rating. Solar design software that provides SAP-compatible output — specifically, the annual kWh/m² yield figure and system specifications in a format that SAP assessors can use directly — eliminates the data translation step between design completion and SAP submission.

EPC support for retrofit. Where a solar PV retrofit installation is part of an energy efficiency improvement package, the EPC assessor needs accurate generation data from the design software. Output formatted for EPC assessors, rather than requiring assessors to interpret a system specification and perform their own calculations, reduces errors and strengthens the professional relationship between the installer and the assessor network.

Smart Export Guarantee (SEG) Calculations

The Smart Export Guarantee replaced the Feed-in Tariff export payment from January 2020 and is now the primary financial mechanism for residential solar export earnings in the UK. Under SEG, electricity suppliers with 150,000 or more customers are required to offer an export tariff to eligible generators. SEG rates vary significantly between licensees — from below 4p/kWh to above 15p/kWh at the time of writing — and rates change regularly.

For the customer proposal, SEG earnings are a meaningful part of the financial case, particularly for systems without battery storage where export fractions are higher. Accurate SEG calculation requires:

• Accurate annual generation estimate from the design simulation (PVGIS-UK or equivalent irradiance dataset)
• Export fraction modelling based on household occupancy profile and self-consumption assumptions
• Current SEG rate input — either a live rate feed or a manually entered rate from the chosen licensee
• Presentation of projected annual SEG income in the customer proposal alongside self-consumption savings

For a typical UK residential system of 4 kWp with no battery storage in a South-oriented installation, annual generation is approximately 3,400–3,800 kWh depending on location. With a 50% export fraction, annual SEG income at 10p/kWh is £170–190. That figure is meaningful in a proposal financial model, and errors in generation estimation or export fraction assumptions directly affect customer decision-making.

Software that models export fraction from load profile data — rather than applying a generic industry default — produces significantly more accurate SEG income projections. Generic defaults (often 50% for residential without storage) can be off by 15–25 percentage points for specific households, which translates to meaningful proposal inaccuracy.

DNO Notification and Application Documentation

Every UK solar installation requires engagement with the relevant Distribution Network Operator. For G98 systems, this is a notification. For G99 systems, this is a formal application. The documentation requirements vary by DNO — UK Power Networks, Western Power Distribution (now National Grid ED), Scottish and Southern Electricity Networks, Northern Powergrid, and SP Energy Networks each have specific formats and portal requirements — but the core data elements are consistent.

A complete DNO notification or application pack includes:

• Installer details and MCS certificate number
• Site address and MPAN (meter point administration number)
• Inverter make, model, and certification status (must appear on ENA’s approved inverter list)
• System rated output (kWp and kWAC)
• Export limitation details (where applicable)
• Single-line diagram
• Protection relay settings documentation (G99 only)

Software that generates DNO packs automatically from the completed design — with inverter data pulled from a current ENA-approved database — eliminates the manual assembly step. Errors in DNO packs are the second most common cause of notification delays after incomplete data: an inverter model not matching the ENA approved list, or a rated output discrepancy between the design specification and the notification form, triggers a rejection that resets the processing clock.

Best Solar Design Software for UK Installers 2026

Deep Dive: SurgePV for UK Installers

SurgePV is designed around the operational reality of UK solar installation: compliance documentation is not a byproduct of the design — it is half the job. The platform’s UK-specific feature set reflects that reality, automating the compliance stack that consumes the most installer time while maintaining the design accuracy that MCS audits and G99 technical reviews demand.

PVGIS-UK Irradiance and Yield Simulation

SurgePV uses the PVGIS 5.3 irradiance dataset for UK installations, supplemented with Meteonorm’s UK regional climate data for locations where PVGIS spatial resolution is insufficient. PVGIS 5.3 incorporates ERA5 reanalysis climate data, which significantly improves accuracy over previous PVGIS releases for UK high-latitude and coastal sites where older datasets showed systematic biases.

The yield simulation runs at hourly time steps across a full year (8,760 hours), incorporating the site’s actual roof geometry and 3D shade model. The output is a monthly generation profile and annual kWh yield, with loss factor breakdown: irradiance, temperature, shading, wiring, inverter, and soiling. This loss factor breakdown is required for MCS documentation and provides the supporting data for G99 yield assessment submissions.

For UK residential sites in optimal South-facing orientations, SurgePV’s yield simulation achieves ±1.5% annual deviation against measured performance data from commissioned systems in the PVGIS validation dataset. For East/West split arrays — increasingly common on pitched residential roofs — the simulation correctly handles the bifurcated generation profile, which is a source of significant error in platforms using simplified irradiance averaging.

G98/G99 Real-Time Compliance Engine

As the system design takes shape — inverter selection, module count, string configuration — SurgePV’s G98/G99 compliance engine monitors the system against the ENA thresholds in real time. When a design crosses the G98/G99 boundary, the platform flags it immediately on the design canvas, before the installer has committed to the configuration.

This real-time validation matters because the G98/G99 boundary affects the entire project timeline. A residential installer who designs a 4 kWp single-phase system assuming G98 notification and then discovers at submission that the inverter’s rated AC output crosses the G99 threshold is looking at a 45–65 working day delay before the grid connection can proceed. Catching that boundary at design time, not submission time, is the difference between a project that completes on schedule and one that sits idle for three months.

The compliance engine also validates inverter export limitation settings. For systems designed with export limitation — common on G99 applications where the DNO requires zero export or a capped export rate — the platform checks that the inverter’s export limitation firmware is correctly specified and that the design documentation reflects the limitation configuration.

MCS 012 String Sizing Automation

String sizing for MCS compliance is not complicated in principle, but it is time-consuming and error-prone when done manually at volume. The calculation requires:

• Maximum string voltage at minimum temperature for the installation location (using the STC Voc of the selected module, the temperature coefficient of Voc, and the minimum recorded temperature for the site)
• Minimum string voltage at maximum temperature (using Vmpp, the temperature coefficient of Vmpp, and the maximum recorded temperature)
• Verification that maximum Voc stays within the inverter’s absolute maximum input voltage
• Verification that minimum Vmpp stays within the inverter’s MPPT operating window
• String current check against inverter maximum input current per MPPT channel

SurgePV runs this calculation automatically for the selected module and inverter combination, using PVGIS climate data to extract the design temperature range for the installation postcode. The output is a string sizing calculation table that meets MCS 012 documentation requirements — ready to include in the MCS installation documentation pack without manual re-creation.

For a UK installer processing 30 projects per month, automated MCS string sizing saves approximately 45 minutes per project versus manual calculation and documentation — 22.5 hours per month, or the equivalent of three working days recovered for productive installation work.

DNO Notification Pack Generation

SurgePV generates complete DNO notification packs for G98 submissions, formatted for each of the major UK DNOs. The pack is populated automatically from the completed design: installer details, MCS certificate number, site MPAN, inverter data drawn from the ENA-approved inverter database, system rated output, and single-line diagram.

The ENA-approved inverter database within SurgePV is maintained against the current ENA Type Test database. When an inverter is selected for a design, the platform verifies it against the approved list and flags any discrepancies. Inverters that appear on the ENA list under a specific firmware version requirement are flagged with that requirement in the DNO pack, reducing the risk of a rejection due to inverter model/firmware specification mismatch.

For G99 applications, SurgePV generates the Stage 1 screening data in the format required by each DNO, including the technical specification data that triggers or avoids a Stage 2 study requirement. While Stage 2 studies themselves are outside the scope of design software — they require power systems engineering expertise — software that correctly populates the Stage 1 data, and flags design parameters that are likely to trigger a Stage 2 review, gives the installer visibility before the submission is made.

SEG Financial Modelling

SurgePV’s proposal module includes SEG financial modelling as a core feature, not an optional add-on. The financial model requires three inputs: annual generation estimate from the completed design, export fraction from the household occupancy profile, and the SEG rate from the installer’s chosen licensee.

The platform provides export fraction guidance based on household size and occupancy assumptions — a two-person household with weekday working patterns exports a higher fraction of generation than a family home with daytime occupancy. For installers who gather load data from customer bills (average daily consumption, time-of-use patterns), SurgePV can apply that data directly to the export fraction calculation, producing a more accurate SEG income projection than a generic default.

The proposal output shows:

• Annual generation estimate with loss factor breakdown
• Estimated self-consumption (kWh and value at current domestic tariff)
• Estimated export (kWh)
• SEG income at the entered rate (annual)
• 25-year financial projection with assumed tariff and SEG rate escalation
• Simple payback period and NPV at a configurable discount rate

For battery storage systems, the model adjusts the export fraction downward (more self-consumption) and shows the additional financial benefit of storage against the cost of the battery unit — the calculation that most customers need to make a decision on whether to include storage at installation.

Integrated Proposal Workflow

The solar proposal software in SurgePV is the output layer of the same workflow as the design and compliance tools — not a separate application requiring data re-entry. After the design is complete and compliance documentation is generated, the proposal is built from the same data: system specification, yield estimates, financial model, SEG calculations, and any available satellite or aerial imagery of the customer’s property.

The result is a proposal that reflects the actual designed system — not a templated estimate with manually entered parameters that may drift from the final design. For UK residential sales, where proposals are typically presented at the kitchen table and customers compare multiple quotes, the visual quality and data accuracy of the proposal document directly influences close rate.

Other UK Solar Design Platforms

Aurora Solar — Enterprise Standard for Large Portfolios

Aurora Solar is the dominant platform for large-scale solar enterprises globally. In the UK market, its LIDAR-based 3D modelling is best-in-class for complex commercial rooftops, and its financial modelling engine is mature. Aurora has strong penetration among UK solar EPCs and aggregators managing multi-site residential portfolios.

Genuine strengths:

• LIDAR precision for complex commercial and industrial rooftops
• Advanced financial modelling with multi-scenario outputs
• Strong CRM integration for enterprise pipeline management
• Cloud-based multi-user collaboration for large design teams

Real limitations for UK installers:

• UK-specific compliance features — G98/G99 validation, DNO pack generation, MCS documentation — are not core platform features. UK compliance workflows require significant manual supplementation.
• PVGIS irradiance integration is available but not the primary data source; US-weighted irradiance sources can introduce systematic biases on UK sites.
• Enterprise pricing is prohibitive for UK installers under 100–200 projects per month. The per-seat cost at smaller teams eliminates the ROI case relative to UK-specific mid-tier alternatives.
• Proposal tools are modular add-ons, not a unified design-to-proposal workflow. Data handoffs between Aurora’s design module and proposal module require manual QA.

Best for: Large UK solar EPCs and residential aggregators with 300+ projects per month, dedicated engineering design teams, and the implementation investment to build UK compliance processes around the platform’s technical strengths.

Honest assessment: Aurora Solar is excellent software. For UK installers whose primary bottleneck is MCS documentation, G98/G99 submission quality, and proposal speed — rather than LIDAR modelling precision — the complexity and price premium are difficult to justify against UK-specific mid-tier platforms.

PV*Sol — The Architectural 3D Benchmark

PV*Sol from Valentin Software is the long-standing reference platform for detailed 3D building simulation. Its 3D modelling environment is more capable than any other platform for architecturally complex installations — listed buildings, mixed orientations, unusual roof geometries, integrated PV facades.

Genuine strengths:

• Best-in-class 3D architectural visualisation — useful for planning consent submissions on complex buildings
• Granular shading simulation including horizon shading and near-shading objects
• Broad module and inverter database with European product coverage
• Battery storage simulation including time-of-use tariff modelling

Real limitations for UK installers:

• No automated G98/G99 validation or DNO pack generation. These are manual steps requiring separate documentation assembly.
• MCS documentation is not auto-generated from the design. String sizing calculations are performed within the software but must be extracted and formatted separately for MCS compliance packs.
• Desktop-based workflow limits cloud collaboration for teams with multiple designers or remote working arrangements.
• Higher learning curve than cloud-native platforms — full proficiency typically requires two to four weeks.

Best for: UK installers specialising in architecturally complex installations — listed buildings, unusual roof geometries, integrated PV systems — where 3D accuracy and visual presentation quality for planning consent are the primary requirements.

Honest assessment: PV*Sol is genuinely excellent for complex architectural projects. For standard UK residential and straightforward commercial rooftop work — where 3D modelling precision is less critical than documentation automation — the desktop workflow and absent UK compliance automation make it a poor fit for volume operations.

Helioscope — Cloud Simplicity for Commercial Flat-Roof Work

Helioscope (now part of Aurora Solar) delivers reliable energy simulations with a low learning curve. It remains popular among UK commercial EPCs focused on flat-roof industrial and retail installations.

Genuine strengths:

• Fast layout tools for commercial flat roofs and simple pitched rooftop configurations
• Accurate energy simulations for standard commercial projects
• Cloud-based with straightforward multi-user access
• Accessible pricing for commercial-focused teams

Real limitations for UK installers:

• No G98/G99 compliance validation, no MCS documentation generation, no DNO pack output. UK compliance workflows are entirely manual.
• 3D modelling for complex residential rooftops is simplified. Multi-plane pitched roofs with dormers, chimneys, and mixed orientations are where Helioscope’s approach introduces design inaccuracies.
• Proposal output is basic PDF export, not a financial storytelling document with SEG modelling and 25-year projections. For UK residential sales, this is a meaningful competitive disadvantage.
• Irradiance accuracy for UK high-latitude and coastal sites is weaker than PVGIS-native platforms.

Best for: UK commercial EPCs focused on straightforward flat-roof installations where simplicity of operation outweighs the need for UK-specific compliance automation.

PVcase — Ground-Mount Engineering Precision

PVcase integrates with AutoCAD and Civil 3D for detailed mechanical and electrical layouts on ground-mount and large commercial rooftop projects. Its terrain analysis and auto-stringing logic are designed for the engineering demands of large ground-mount solar farms.

Genuine strengths:

• CAD integration for detailed mechanical layouts on ground-mount sites
• Terrain analysis and slope modelling for complex site topography
• Precise auto-stringing with detailed electrical balance of plant documentation
• Strong for utility-scale and large industrial ground-mount engineering in the UK

Real limitations:

• No UK residential workflow capability
• No G98/G99 validation, no MCS documentation, no DNO notification generation
• High cost and steep CAD skill requirement
• Output is engineering documentation for construction, not customer proposals or compliance submissions

Best for: UK ground-mount solar engineering firms producing construction documentation for large commercial and utility-scale projects where CAD-based engineering output is the deliverable.

MCS Certification and Software Requirements

MCS certification is the foundation of the UK solar industry’s quality framework. Every installation claiming Smart Export Guarantee payments, accessing certain green finance products, or involved in a government energy efficiency programme must be installed by an MCS-certified company using MCS-certified products. Understanding what MCS requires — and where software automates the compliance burden — is essential for any UK installer evaluating design tools.

What MCS Audits Check

MCS audits operate on a sampling basis. An auditor selects a subset of recent installations and reviews the documentation for each against the MCS Installation Standard. The documentation reviewed includes:

Pre-installation:

• Customer agreement and system specification
• String sizing calculation demonstrating MCS 012 compliance
• Shading analysis and yield estimate using an approved methodology

Installation:

• Installation checklist (MCS Installation Standard section compliance)
• Product certificates for all MCS-certified components (modules, inverter, mounting system)

Commissioning:

• Commissioning record including inverter commissioning parameters, grid connection status, and initial yield reading
• G98 notification confirmation or G99 acceptance letter

Post-installation:

• Customer handover pack including operating instructions, warranty information, and SEG registration guidance

Documentation gaps in any of these categories result in a non-conformance. The number of non-conformances across the sampled installation set determines whether the installer’s MCS certification is maintained, placed under enhanced surveillance, or subject to suspension proceedings.

Software that auto-generates the string sizing calculation, yield estimate, and design specification from the completed design — and that maintains a documentation record for each project — dramatically reduces the audit risk surface. The installer’s role shifts from assembling documentation manually for each project to verifying that the software-generated documentation is complete before the project file is closed.

String Sizing: The MCS 012 Detail

MCS 012 string sizing methodology is specific about the temperature correction required. The calculation uses the lowest recorded mean monthly temperature for the installation location, not an absolute minimum temperature. PVGIS provides this data for any UK postcode; software that uses actual location-specific climate data rather than a conservative national default produces more accurate string configurations that maximise system performance within safe operating limits.

The common manual error is using a conservative temperature assumption — for example, -20°C — that results in over-restrictive string lengths, reducing system size below the roof capacity. For a 10 kWp commercial system, a two-module per string reduction due to an overly conservative temperature assumption reduces annual generation by approximately 400–600 kWh — a meaningful yield loss that affects both the customer’s financial return and the proposal’s competitiveness.

Software-automated MCS 012 string sizing using PVGIS location-specific temperature data eliminates this error. The calculation is correct by default, and the output documentation is in MCS-compliant format.

G98/G99 Grid Connection Process in Detail

Understanding the G98/G99 process — not just the threshold, but the full workflow — helps installers appreciate where software support has the highest leverage.

G98 Process: End-to-End

A standard G98 residential installation workflow:

1. Design phase. Software confirms system is within G98 limits. Inverter verified on ENA approved list. System output and configuration finalised.

2. G98 notification preparation. Software generates G98 notification form with installer details, MCS number, site MPAN, inverter data, and system specification. Some DNOs accept the standard ENA G98 notification form; others have proprietary portal submission forms — the data elements are consistent but the format differs.

3. Notification submission. Notification submitted to the DNO via the relevant portal (UK Power Networks, National Grid ED, SSEN, Northern Powergrid, or SP Energy Networks). Digital submission portals have dramatically reduced processing times — most G98 notifications are processed within 48–72 hours.

4. 20-working-day objection period. The DNO has 20 working days to object to the connection. In practice, with no technical flags, most G98 notifications proceed without objection and the system can be installed and energised.

5. Commissioning and registration. System commissioned. DNO notified of commissioning (some DNOs require a separate commissioning notification). MCS certificate issued. SEG registration initiated.

Where software adds value in the G98 process: step 1 (real-time G98 threshold validation), step 2 (automated notification pack generation), and step 5 (commissioning data for MCS documentation).

G99 Process: The Critical Path

G99 is where project delays accumulate. The timeline is longer, the documentation requirements are more demanding, and errors at any stage can trigger a restart of the processing clock. The full G99 process:

Stage 1 Screening (all G99 applications):

The installer submits the Stage 1 screening application with:

• Site address and connection point
• Inverter type, rated output, and control parameters
• Export limitation details (if applicable)
• Protection relay type and settings

The DNO reviews the Stage 1 data and determines whether the system can be approved directly (no Stage 2 study required) or whether a Stage 2 power systems study is needed. For standard commercial systems in areas of the distribution network with sufficient capacity, Stage 1 approval is common. For systems in constrained network areas or with unusual parameters, a Stage 2 study is required.

Stage 1 decisions typically take 45–65 working days. This is the critical path item for commercial projects in the UK — the DNO approval is frequently on the critical path for construction start, and any resubmission adds the full timeline again.

Stage 2 Study (where required):

A Stage 2 power systems study is conducted by the DNO’s engineering team. The study models the impact of the generating unit on the local network — voltage rise, fault level, protection coordination. The outcome is either approval (with or without conditions) or rejection (where the network cannot accommodate the system without reinforcement).

Stage 2 studies can take 3–6 months for complex applications in constrained network areas. Software cannot accelerate a Stage 2 study, but it can ensure that the Stage 1 submission data is complete and accurate — avoiding the resubmission delays that are most common where Stage 1 data errors prevent the DNO from initiating the study.

G99 Acceptance Letter:

On approval, the DNO issues a G99 acceptance letter specifying the technical parameters of the approved connection — export limit, protection relay settings, commissioning test requirements. The system cannot be installed or energised before this letter is received.

Commissioning and Connection:

After installation, the system must be commissioned against the G99 acceptance letter parameters. The commissioning record, including protection relay test results, is submitted to the DNO to complete the connection registration.

SEG Calculations: Getting the Numbers Right

The Smart Export Guarantee is the primary ongoing financial benefit for UK residential solar customers post-installation. Getting the SEG calculation right in the proposal is important — both for proposal accuracy and for managing customer expectations about the financial return.

The Export Fraction: The Number Most Often Wrong

The export fraction — the proportion of total annual generation that is exported to the grid — is the most commonly misestimated variable in UK solar proposals. The generic industry assumption of 50% export for residential systems without storage is directionally correct for an average household, but individual household export fractions range from 25% to 75% depending on:

• Household size and occupancy patterns (daytime versus evening load profiles)
• Appliance mix (electric vehicle charging, heat pumps, and high-draw daytime appliances reduce export significantly)
• Season (summer export fractions are higher than winter on most residential profiles)
• Roof orientation (East/West split arrays have higher self-consumption than South-facing arrays due to flatter generation profiles)

For a household with a heat pump running during the day, the export fraction may be 25–30%. For a two-person retired household in a South-facing property with no EV or heat pump, the export fraction may be 65–70%. Applying the generic 50% default to either household introduces a significant SEG income error in the proposal — and a customer relationship problem when actual export income differs from the projected figure.

Design software that applies occupancy-adjusted export fraction modelling — rather than a fixed default — produces meaningfully more accurate SEG projections. Some platforms allow the installer to input monthly utility bill data and derive an export fraction from measured consumption patterns. This is the most accurate approach for proposals where the installer has gathered customer data.

SEG Rate Selection and Proposal Presentation

SEG rates vary significantly between licensees. At the time of writing, rates range from below 4p/kWh for the largest obligated suppliers to above 15p/kWh for competitive smaller suppliers. Rates change regularly — some suppliers update rates monthly, others quarterly. The rate the customer selects, and when they register, affects their SEG income.

For the proposal, there are two approaches to SEG rate presentation:

Conservative approach: Use the current rate from the customer’s existing electricity supplier (who is likely an obligated SEG licensee). This reflects the rate available with no additional switching effort and understates the maximum potential SEG income.

Optimised approach: Present the current best available rate from an approved SEG licensee and note that the customer can register with any licensee regardless of their electricity supplier. This maximises the projected SEG income and can be a meaningful differentiator in the proposal — but requires the customer to take an additional registration step.

The best proposal presentation shows both: the conservative rate as the baseline and the optimised rate as an available uplift, with guidance on how to register.

Battery Storage and SEG Interaction

For systems with battery storage, the SEG calculation becomes more nuanced. Battery storage reduces the export fraction — more generation is self-consumed via the battery rather than exported — but increases the value of self-consumption by allowing stored generation to displace evening grid import at potentially higher unit rates.

The financial analysis for a battery storage system requires:

• PV generation model (from the design simulation)
• Battery charge/discharge model (capacity, round-trip efficiency, charge/discharge rate)
• Household load profile (to determine when storage is needed versus when generation can be consumed directly)
• SEG rate for remaining export
• Grid import tariff for remaining grid purchases (including time-of-use tariff structure where applicable)

Software that integrates all five inputs — rather than treating the battery as a simple reduction in export fraction — produces a materially more accurate financial model. The value of battery storage is highly sensitive to the time-of-use tariff differential between export rate and peak import rate; software that models this correctly presents a more compelling (or more honest) case for storage inclusion.

DNO Application Documentation: What Each DNO Expects

The UK has five main Distribution Network Operators for England, Scotland, and Wales (plus NIE Networks for Northern Ireland). Each has its own submission portal and specific documentation requirements, though the underlying data is consistent across all.

UK Power Networks (UKPN) — London, South East, East of England

UKPN operates one of the UK’s largest G98/G99 portal systems. Their G98 notification process is entirely digital via the UKPN self-service portal. G99 applications are submitted through a separate formal application portal. UKPN has been one of the faster DNOs for G98 notification processing — typically 24–48 hours for straightforward submissions.

Key UKPN-specific requirements:

• Inverter must appear on the current ENA Type Test register with exact model name match
• MPAN must be entered in the standard 13-digit format
• For G99, protection relay settings must be provided in the format specified in G99 Appendix A1

National Grid Electricity Distribution (NGED) — Midlands, South West, South Wales

Formerly Western Power Distribution. NGED completed its DNO rebranding in 2023. The submission portal is fully digital for both G98 and G99 applications. NGED has invested in digital processing infrastructure, resulting in improved G98 processing times.

Key NGED-specific requirements:

• Export limitation confirmation is required for commercial systems above 16A per phase even for systems not requiring export limitation, confirming the inverter is not configured for excess export
• G99 Stage 1 applications require the installer’s MCS certificate number as a mandatory field

Scottish and Southern Electricity Networks (SSEN) — South of England, Northern Scotland

SSEN covers two geographically separate licence areas. The South of England licence area covers Hampshire, Dorset, parts of Berkshire and Wiltshire. The North of Scotland licence area covers Highlands, Islands, and Grampian. Processing times in the North of Scotland licence area can be longer than the England-based DNOs due to network constraint complexity in remote and island locations.

Key SSEN-specific requirements:

• North of Scotland applications may require additional feasibility information for properties in constrained network areas
• Island connections (Orkney, Shetland, Western Isles) have specific embedded generation requirements that may differ from mainland Grid Code requirements

Northern Powergrid — North East England, Yorkshire

Northern Powergrid’s digital submission portal handles G98 notifications and G99 Stage 1 applications. Processing times are competitive with other major DNOs for standard applications.

Key Northern Powergrid-specific requirements:

• G99 applications above 50 kWp require a completed Embedded Generation Connection Agreement
• Annual yield data in MWh must be provided as a mandatory field on G99 Stage 1 applications

SP Energy Networks — Central and Southern Scotland, Merseyside, Cheshire

SP Energy Networks covers two licence areas: SP Manweb (Merseyside and Cheshire) and SP Distribution (Central and Southern Scotland). The submission portal serves both licence areas with separate processing queues.

Key SP Energy Networks requirements:

• SP Manweb and SP Distribution applications are processed by separate teams; the MPAN determines which queue the application enters
• G99 applications require confirmation of the commissioning test methodology in advance of installation

Choosing by Business Size and Project Type

Key Decision Factors by Business Stage

Early stage (under 15 projects/month). At this volume, the primary risk is MCS audit exposure from documentation gaps — a single non-conformance at a small sample size has an outsized impact on the audit outcome. SurgePV’s automated documentation generation eliminates the most common documentation gap categories. The mid-tier pricing is accessible without large volume to amortise against.

Growth stage (15–100 projects/month). This is where manual compliance workflows break down. The first constraint is typically documentation assembly time consuming designer hours that should be spent on new designs. The second is DNO submission errors generating delays that create cash flow problems. SurgePV’s automation directly addresses both. For installers also managing battery storage across a growing proportion of projects, the integrated storage modelling in SurgePV prevents the yield calculation errors that become more frequent as project complexity grows.

Scale stage (100+ projects/month). Platform architecture matters at this volume. Multi-user performance, project status tracking, and batch documentation generation become critical. SurgePV’s cloud architecture supports this; Aurora Solar is the alternative for installers whose primary need at scale is enterprise CRM integration and portfolio analytics rather than UK compliance automation.

The ROI of UK Solar Design Software

Quantifying the return on a solar design software subscription requires accounting for all the ways manual workflows cost time and money — not just the design hours, but the compliance documentation, the DNO submission errors, the audit risk exposure, and the proposal quality gap that affects close rate.

At a designer cost of £30/hr (mid-range for a UK solar designer), 66 hours recovered per month represents £1,980 of designer time recaptured for productive work. For a design team handling 30 projects per month, this is the equivalent of recovering 1.5 working weeks per month.

This calculation does not include:

• Revenue impact of faster proposal delivery (close rate benefit)
• MCS audit risk reduction (potential cost of audit non-conformances and corrective action programmes)
• Customer satisfaction improvement from accurate SEG projections (referral and review value)

For the solar design software ROI case at UK residential volume, the documentation automation is typically the highest-value line item — more so than the design automation itself, because the UK compliance documentation burden is uniquely high relative to other markets.

Future of UK Solar Design Software

The UK solar software market is evolving in several directions that will affect platform selection decisions in 2026 and beyond.

AI-powered roof assessment. LIDAR data coverage for UK residential addresses is improving. Platforms using AI-driven roof geometry extraction from aerial imagery and LIDAR are reducing the time from customer address to completed design from 45–60 minutes to under 10 minutes for standard residential rooftops. The accuracy of AI-extracted roof geometry on UK pitched roofs — which tend to be more geometrically complex than US residential rooftops due to mixed orientations, valleys, dormers, and chimney stacks — has been the main barrier to widespread adoption. As AI model accuracy improves, manual roof tracing will become a legacy workflow.

EV charging integration. With UK EV adoption accelerating, solar PV proposals increasingly need to model the interaction between PV generation and EV charging load profiles. The combination of a home solar system, a battery storage unit, and a smart EV charger creates a self-consumption optimisation problem that simple export fraction defaults cannot handle. Software that integrates EV charging load profiles into the SEG export calculation will produce more accurate financial models — and more compelling proposals — for the growing segment of customers considering the full package.

Live Ofgem and DNO data integration. SEG rates change regularly, and DNO constraint data (network capacity availability by postcode) is increasingly available via API. Platforms that integrate live Ofgem SEG rate data and DNO network capacity data will be able to flag SEG rate changes automatically and identify postcodes where G99 Stage 2 studies are likely before the Stage 1 submission is made.

Automated SAP and EPC integration. As the UK builds the digital infrastructure for energy data sharing (particularly under the Smart Energy Code and the Digitalisation of Energy programme), design software will increasingly be able to pass yield and specification data directly to SAP assessors and EPC tools without manual export steps. This will be particularly valuable for new-build pipelines where the interaction between installer, SAP assessor, and developer is currently a manual data exchange process.

Time-of-use tariff optimisation. With Ofgem’s default tariff reforms and the growth of time-of-use tariffs (Octopus Agile, British Gas Electric Driver, OVO EV Everywhere), the financial model for UK solar increasingly depends on the interaction between solar generation, battery storage, EV charging, and time-of-use tariff pricing. Software that models this interaction — optimising the battery charge/discharge schedule against the tariff price curve — will produce financial projections that are not just more accurate but genuinely more compelling for the growing proportion of UK customers who are already on time-of-use tariffs.

Conclusion

The UK solar installation market in 2026 rewards installers who can produce MCS-compliant documentation, accurate G98/G99 submissions, and persuasive SEG-inclusive proposals faster than their competitors. The compliance framework is the highest-friction element of the UK workflow — not the roof design itself.

The right solar design software removes that friction systematically. For UK residential installers, the highest-value capabilities are automated MCS documentation generation, real-time G98/G99 threshold validation, DNO notification pack generation from the completed design, and SEG financial modelling integrated into the customer proposal. For commercial installers, add SAP-compatible output and G99 Stage 1 data generation to that list.

SurgePV is the only platform that covers all of these requirements natively, without manual supplementation. For UK installers evaluating platforms in 2026, the practical test is straightforward: take five real recent projects, run them through each platform’s trial, and compare the documentation output against your MCS audit checklist and your current DNO submission pack. The platform whose output is closest to ready-to-submit — without manual editing — is the right platform for your compliance burden.

For the customer-facing side of the workflow, the solar proposal software integrated into SurgePV ensures that the compliance work and the proposal work happen in the same workflow, not as separate time expenditures. That integration is the operational difference between a design tool that saves designer hours and a platform that materially improves the economics of an installer’s entire workflow.

Frequently Asked Questions

What solar design software do UK installers use?

UK installers most commonly use SurgePV, Aurora Solar, PV*Sol, Helioscope, and PVcase. SurgePV leads for MCS compliance depth, offering real-time G98/G99 grid code validation, DNO notification pack generation, SAP calculation integration, and Smart Export Guarantee yield modelling — all in a single workflow built specifically for the British market.

Does solar design software need to be MCS compliant in the UK?

MCS certification applies to the installation company and the products used — not to the design software itself. However, the documentation your software produces must meet MCS 012 string sizing standards and MCS installation standards. Software that automates MCS-compliant documentation generation is essential for certified installers who want to minimise audit risk and administrative overhead.

What is the difference between G98 and G99 grid connections in the UK?

G98 governs small-scale single-phase or three-phase PV systems up to 16A per phase (approximately 3.68 kW single-phase). These systems can connect to the grid using a simplified notification process. G99 covers larger systems requiring formal pre-approval from the Distribution Network Operator before installation begins. Most residential systems fall under G98; commercial systems above 3.68 kW single-phase must follow G99 procedures, which involve a formal application, technical review, and a DNO approval letter before the inverter can be energised.

How do I calculate Smart Export Guarantee payments in solar design software?

SEG payment calculations require accurate annual yield estimates from the design software, combined with the SEG rate offered by the installer’s chosen licensee. Software should model the export fraction — the proportion of total generation that is exported rather than self-consumed — using occupancy profiles and load data. For a typical UK residential system with no battery storage, export fractions range from 40% to 60% of total annual generation. Multiplying the estimated annual export by the SEG p/kWh rate gives the projected annual SEG income, which feeds directly into the customer proposal.

What is the best free solar design software for UK installers?

PVGIS (from the European Commission’s Joint Research Centre) is the most widely used free irradiance and yield estimation tool for UK sites. It provides location-specific irradiance data and basic yield estimates. However, it does not produce MCS documentation, G98/G99 compliance packs, DNO notification letters, or customer proposals. For full workflow automation including MCS-compliant documentation, professional proposals, and grid code validation, a commercial platform such as SurgePV is necessary.

How long does G99 pre-approval take in the UK?

G99 pre-approval currently takes 45–65 working days for standard Stage 1 applications across most UK DNOs. Applications that trigger a Stage 2 power systems study can take 3–6 months in constrained network areas. Submission timeline is critical: installers who submit the G99 application at contract signature — before design finalisation, procurement, or installation scheduling — keep the DNO approval on a parallel track rather than the critical path. Software that generates G99 Stage 1 data from a preliminary design enables early submission.

Which DNO regions in the UK have the longest G99 processing times?

Processing times vary by DNO region and network congestion. The North of Scotland licence area (SSEN North) has historically had longer processing times due to network constraint complexity in remote and island locations. Suburban and urban areas in constrained distribution zones across all DNO regions can also experience longer Stage 2 study timelines. For specific postcode-level constraint information, most DNOs now publish network capacity heat maps that indicate where Stage 2 studies are likely.

Does solar design software handle battery storage calculations for UK installations?

The leading UK-focused platforms, including SurgePV, include battery storage modelling that integrates with the PV generation simulation and load profile data. A complete battery storage model calculates annual self-consumption with storage, remaining export (and therefore SEG income), grid import reduction, round-trip efficiency losses, and payback period. For UK proposals where battery storage is an increasingly common upsell, accurate storage financial modelling is a material competitive advantage. Software that treats battery storage as a simple export fraction reduction — rather than modelling charge/discharge cycles against the load profile — produces systematically inaccurate financial projections for battery-inclusive systems.

How does SAP integration work in solar design software for UK new-builds?

SAP 10.2 is the current standard for UK new-build energy performance calculations. For solar PV, SAP requires the annual kWh/m² yield and system specification in a format that SAP assessors can enter into their assessment software (typically SAP 10 Reduced Data SAP or full SAP). Solar design software that exports yield data in SAP-compatible format eliminates the manual transcription step between the designer’s output and the SAP assessor’s input. SurgePV provides SAP-compatible output from the completed design; other platforms typically require manual extraction and reformatting.

What should I look for when evaluating UK solar design software on a free trial?

Run five real recent projects through the trial platform and check: (1) Does the G98/G99 threshold validation correctly identify your G99 systems? (2) Is the MCS string sizing calculation output in a format ready for your audit file? (3) Does the DNO pack generation produce output that matches your current DNO’s format requirements? (4) Is the SEG financial modelling accurate for your customer’s load profile? (5) Time the complete workflow from postcode entry to completed proposal. Most platforms including SurgePV offer free trials. Do not commit based on a vendor demo alone — the documentation output quality is only visible when you run real project data through the system.