Background — the energy challenge
The company — a family-owned ambient and chilled food manufacturer employing 140 staff at its single Midlands production site — had seen its annual electricity bill rise from £190,000 in 2020 to £310,000 by 2023 at the height of the post-Ukraine energy price surge. Although prices had moderated by 2024 to approximately £265,000 per year, the company's Finance Director and Operations Manager had concluded that energy price exposure was a structural risk to the business model that needed addressing permanently, not merely through short-term contract fixing.
The factory operates Monday to Friday, 06:00–22:00, with a skeleton Saturday morning shift for maintenance and cleaning. Its electricity load profile is relatively consistent: refrigeration and cold store compressors run continuously, production lines operate from 07:00–19:00, and HVAC, lighting and ancillary systems fill the remainder. Half-hourly metering data confirmed that between 07:00 and 19:00 on weekdays, the site was consuming between 280 and 450 kW at any given time, providing an excellent foundation for solar self-consumption.
The company was also subject to ESOS Phase 3 obligations (with Phase 4 compliance due by December 2027) and had received requests from two major retail customers asking for Scope 2 emissions reduction data as part of their supplier sustainability assessments. Solar energy was identified in the ESOS audit as the single highest-return energy saving measure available to the business.
The roof of the main production building — a portal-frame structure built in 1994, extended in 2007 — offered approximately 3,400 m² of usable roof area across two south-facing slopes and a large flat section over the warehouse and cold store. A structural survey confirmed that the roof was in good condition and could support a ballasted mounting system without modification, eliminating the need for costly roof repairs prior to installation.
System specification
After receiving proposals from four installers and conducting reference checks with two previous clients of each, the company selected a specialist commercial solar installer with experience in food manufacturing environments — specifically important for the need to maintain food safety standards and HVAC system access during installation.
| Component | Specification | Quantity / Detail |
|---|---|---|
| Solar panels | Jinko Solar Tiger Neo N-type 400W bifacial monocrystalline | 875 panels; 25-year power warranty at 87.4% output |
| Inverters | SolarEdge SE175K string inverter (G99 compatible) | 2 x 175 kW units; 12-year warranty extended to 20 years |
| Optimisers | SolarEdge P730 DC power optimisers | 875 units (one per panel); module-level MPPT; 25-year warranty |
| Mounting — flat roof | K2 Systems RoofFlex ballasted flat-roof mounting | 600 panels at 10-degree tilt; wind load engineered for Midlands zone |
| Mounting — pitched roof | K2 Systems FlatFix penetrating purlins fixing | 275 panels on 22-degree south-facing slope; penetrating fixings to steel purlins |
| Export limiting | SolarEdge Export Limitation Controller with CT clamps | DNO-required 100 kW export limit enforced at inverter level |
| Monitoring | SolarEdge monitoring portal with energy dashboard | Real-time generation, consumption, self-consumption and export data |
| Grid connection | G99 connection to Western Power Distribution (now National Grid ED) | 100 kW export limit; connection offer accepted after 13-week determination |
| Total installed cost | £247,000 ex-VAT | Including all equipment, installation, G99 application, commissioning |
The choice of power optimisers alongside string inverters (rather than a simpler string-only system) was driven by the mixed roof layout. The pitched and flat sections face different orientations and tilt angles, and the pitched section is partially shaded by a plant room and ventilation stacks in the afternoon. Module-level optimisers mitigated the impact of this shading by preventing underperforming panels from reducing the output of unshaded strings — an important consideration in maximising yield from a mixed layout.
The DNO (National Grid Electricity Distribution, formerly Western Power Distribution) imposed a 100 kW export limit as a condition of the G99 connection offer, reflecting constraints on the local 11 kV network. This meant that generation above 100 kW that could not be consumed on-site would need to be curtailed. The export limiting controller managed this automatically, throttling inverter output when grid import fell below zero. The impact on annual generation was modelled at approximately 8,500 kWh per year — a modest reduction given the factory's high base load.
The installation process
The on-site installation was completed over 9 working days in February 2025, with two crews of four working simultaneously on the flat roof and pitched roof sections. Working in February was a deliberate choice — it avoided the peak summer period when solar installer lead times are longest, and the shorter days meant the work did not interfere with morning and evening production shift changes. The factory operated normally throughout the installation period with no production downtime.
Days 1–2: Roof preparation and mounting installation
Ballast blocks (pre-calculated per the structural engineer's wind uplift calculations for the specific roof zone) were craned to the flat roof. K2 FlatFix racking profiles were fixed to steel purlins on the pitched section using self-drilling fasteners with EPDM washers. All roof penetrations were sealed with bonded flashing and checked for water tightness before any cabling began. Safety line anchor points were installed around the flat roof perimeter for ongoing maintenance access.
Days 3–5: Panel installation and DC cabling
Panels were installed row by row using a scissor lift platform. DC cables were routed in UV-resistant conduit to the two inverter locations inside the plant room. Optimiser units were clipped to the mounting rail below each panel and connected in the factory. All DC cabling was labelled and tested at string voltage before inverter connection. The installer's electrical team worked alongside the factory's own electrician throughout to maintain compliance with the factory's permit-to-work system.
Days 6–7: AC connection and metering
The two inverters were connected to a new dedicated AC distribution board in the plant room, which was in turn connected to the main LV switchroom via a new fused switch. CT clamps for the export limiting controller were fitted to the incoming supply cables in the main switchroom. The half-hourly export meter specified by the DNO was fitted by a DNO-approved metering specialist (an AMO — Approved Metering Operator) during day 7. This installation required a planned 90-minute supply outage, which was scheduled for 06:00 on a Saturday to avoid production impact.
Days 8–9: Commissioning, testing and sign-off
Full system commissioning included inverter startup and configuration, string-level I-V curve testing, export limit controller calibration and verification (the installer simulated zero-grid-import conditions to confirm limiting function), monitoring portal setup and data connection, and the DNO witness test. The MCS commissioning certificate, G99 commissioning notification to the DNO, and all electrical certificates (BS 7671 minor works / periodic inspection report) were issued on day 9. The factory's energy monitoring platform was integrated with the SolarEdge API to display generation data on the existing energy management dashboard.
Key Installation Note: Food Safety Compliance
All roof work was conducted under a specific risk assessment reviewed by the factory's Technical Manager, addressing the risk of foreign body contamination from roof debris entering the factory. Roof access was strictly controlled via a locked access ladder and no roof works were conducted immediately above open production areas when production lines were active. Roof drainage inspection confirmed no solar installation debris could enter the factory drainage system. The installer provided a post-installation roof cleanliness check and issued a signed declaration confirming no foreign bodies were introduced to the production environment.
Year-one results
The system was commissioned on 14 February 2025 and the following data covers the 12 months to 13 February 2026, as recorded by the SolarEdge monitoring system and independently verified against the factory's half-hourly metering data.
Generation Performance
Financial Performance
The year-one result of £68,400 was 6.3% above the pre-installation projection of £64,350. This outperformance reflected two factors: first, the specific yield came in at 950 kWh/kWp against a P50 of 929 kWh/kWp, following an unusually sunny summer; and second, the electricity buy rate the company was paying averaged 29.8p/kWh over the year, marginally above the 29p/kWh used in the pre-installation model.
The DNO export constraint (100 kW limit) resulted in approximately 9,200 kWh of curtailment during high-generation, low-consumption periods — primarily on Saturday mornings when only the skeleton maintenance shift was operating. This was in line with the 8,500 kWh modelled at design stage. No complaints about export limiting performance were recorded.
Financial analysis: ROI breakdown
The following table provides the complete financial analysis for the project across the first ten years, using the verified year-one performance as the base and applying 3% annual electricity price inflation and 0.5% annual panel degradation thereafter.
| Year | Electricity Rate | Annual Net Saving | Cumulative Net Return |
|---|---|---|---|
| Year 1 (actual) | 29.8p/kWh | £68,400 | -£178,600 |
| Year 2 | 30.7p/kWh | £70,400 | -£108,200 |
| Year 3 | 31.6p/kWh | £72,400 | -£35,800 |
| Year 4 | 32.6p/kWh | £74,400 | +£38,600 (PAYBACK) |
| Year 5 | 33.6p/kWh | £76,500 | +£115,100 |
| Year 10 | 38.5p/kWh | £86,700 | +£537,000 |
| Year 15 | 44.2p/kWh | £98,100 | +£1,037,000 |
| Year 25 | 58.4p/kWh | £124,800 | +£2,210,000 |
Notes: Annual savings based on year-1 actual; electricity rate inflated at 3%/yr; panel degradation at 0.5%/yr; inverter replacement at year 12 assumed at £18,000; annual O&M at £3,500/yr. Year 4 payback assumes simple payback calculation from project completion date. NPV at 8% discount rate: approximately £520,000 on £247,000 investment.
Tax Treatment: Annual Investment Allowance
The £247,000 project cost qualified for 100% Annual Investment Allowance (AIA) in the year of purchase (2025), as it qualified as plant and machinery. At a 25% corporation tax rate, this generated a tax saving of £61,750 in the company's 2024/25 tax year — reducing the effective capital cost to £185,250 and improving the simple payback period from 3.6 years to approximately 2.7 years. All UK businesses should confirm their AIA eligibility with their accountant before finalising their solar investment decision, as the AIA annual limit (£1 million in 2025/26) is shared across all qualifying capital expenditure in the tax year.
Carbon and compliance impact
In year one, the 350 kWp system generated 332,500 kWh of renewable electricity. Using the UK government's published Scope 2 conversion factor for grid electricity (0.233 kgCO2e per kWh for 2025, sourced from the DESNZ Greenhouse Gas Conversion Factors for Company Reporting), total CO2e avoided in year one was 77.5 tonnes — equivalent to the annual emissions of approximately 390 average UK passenger cars, or removing 31 heavy goods vehicles from the road for a year.
This reduction was reported in the company's Streamlined Energy and Carbon Reporting (SECR) submission for financial year 2025/26 as a verified Scope 2 reduction. The MCS certificate, monitoring data and metering records were used as the evidential basis. The carbon saving was independently reviewed by the company's external auditors as part of its annual report sustainability disclosure.
Two major retail customers had requested supplier Scope 2 emissions data as part of their supplier sustainability assessments during 2024. Following installation of the solar system, the company was able to report a 28% reduction in Scope 2 emissions intensity (per tonne of product manufactured) for the 2025/26 reporting year. One customer responded positively to this data, noting the company now met their minimum supplier sustainability threshold; the other had been evaluating whether to transition to an alternative supplier in part due to sustainability concerns, and the company's ability to demonstrate material Scope 2 reduction was cited as a factor in the contract renewal decision.
The installation also contributed to the company's EPC rating for the building, which improved from Band D (energy intensity 125 kWh/m²/yr) to Band C (88 kWh/m²/yr) following reassessment. This is commercially significant as MEES regulations will require commercial properties to achieve EPC Band C for new leases from April 2027. Although the company owns its building, an improved EPC rating positively affects the building's capital value and lettability if the site were ever sold or refinanced.
Lessons learned and what they'd do differently
Reflecting on the project 12 months after commissioning, the company's Operations Manager identified several lessons that would be valuable for other food manufacturers considering a similar installation.
Lesson 1: Start the G99 application earlier
CriticalThe G99 application was submitted three weeks after the initial installer was appointed, waiting for the outline design to be finalised. In retrospect, a preliminary G99 application could have been submitted based on maximum system size at the same time as the formal tender process. The 13-week DNO determination period was the critical path — any delay in submitting the G99 would have delayed the entire project. For future projects, submit the G99 as early as possible, even before the installer is selected.
Lesson 2: Consider battery storage from the outset
RecommendedThe decision not to include battery storage was made primarily on cost grounds at the time of installation. After one year of operation, the monitored data shows 53,200 kWh of generation being exported at 5.5p/kWh (£2,926) that could instead be stored and self-consumed at 29.8p/kWh (£15,854) — a foregone value of approximately £12,928 per year. A 100–150 kWh battery system added at installation time (when civils and electrical infrastructure is already open) would cost approximately £15,000 less than a retrofit installation. The company is now evaluating a battery retrofit for 2026/27.
Lesson 3: Specify the monitoring integration requirements clearly
UsefulThe company's existing energy management platform required a bespoke API integration with the SolarEdge monitoring portal. This was not specified in the original contract and took six additional weeks after commissioning to configure, during which the operations team were reading generation data from two separate platforms. For future installations, specify monitoring integration requirements (API, data format, dashboard integration) in the tender documentation to avoid post-commissioning delays.
Lesson 4: Get three or four quotes, not two
ProcessThe company initially approached only two installers. On the advice of the energy consultant managing the project, a further two were added to the tender process. The spread in quotes received was £247,000 to £298,000 for a comparable specification — a range of £51,000 (21%). The lowest-cost tenderer was selected after due diligence confirmed equivalent technical capability and financial standing. Getting competitive tension into the tender process added meaningful value to the project economics.
Lesson 5: Plan for SEG registration in advance
AdminThe Smart Export Guarantee registration with the electricity supplier took six weeks after commissioning, during which generation that would have been exported was curtailed (due to the export limiting controller defaulting to zero export until SEG was confirmed). Registering for SEG as part of the commissioning process — not as an afterthought — would have recovered approximately £750 of export income in those six weeks. Ensure your installer includes SEG registration as a contractual deliverable at commissioning.
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Trusted Solar Installers Across the UK
We work with a network of MCS-certified regional installers. If you need a recommendation outside our coverage area, these are the firms we trust:
- ALPS Electrical — MCS-certified solar installer — Teesside & North East England
- Midland Solar — Commercial & industrial solar installer — West Midlands
- EC Eco Energy — UK-wide commercial solar & renewables installer
- YEERS — Solar panels & heat pumps — Yorkshire
- Carbon Legacy — Solar & green energy solutions — East Midlands
- D&R Energy — Solar panels & heat pump installer — Bristol & South West