Office Solar Case Study
Reading Thames Valley business park — 1.1 MWp portfolio install
Reading Thames Valley business park — 1.1 MWp portfolio install
A Reading Thames Valley business park landlord with four Grade A office buildings totalling 47,000 sqm wanted to address MEES 2030 compliance across the portfolio in a single procurement cycle. We delivered a unified design across all four buildings — 1.1 MWp rooftop PV, 480 kWh shared battery (located in central plant building), and 24 × 22 kW workplace EV chargers across surface car parks. Service-charge cost recovery structure approved by the four building tenant boards through landlord-led consultation.
The numbers
| Metric | Value |
|---|---|
| System size | 1,100 kWp PV + 480 kWh battery + 24 × 22 kW EV chargers |
| Panel count | 2040 |
| Annual generation | 1,012,000 kWh/year |
| Annual saving | £316,000/year (PV) + £58,000 (EV) |
| Simple payback | 5.4 years |
| Annual CO₂ saved | 230 tonnes |
| EPC uplift | C → A across 4 buildings (avg 11-point gain) |
| Completion | Q1 2026 |
Multi-building procurement approach
Delivering 1.1 MWp across four buildings in a single procurement cycle presented specific project management challenges that would not arise on a single-building install. Each building had a different main electrical board capacity, different roof age and loading certification, and different tenant mix. We addressed this through a unified structural assessment programme (BS EN 1991-1-3 snow loading, BS EN 1991-1-4 wind loading) commissioned across all four roofs simultaneously — saving approximately six weeks and £28,000 in repeated assessment cost compared with sequential single-building procurement.
Grid connection across the four-building estate required a single Tier 2 G99 Export Limitation Agreement with Western Power Distribution (now National Grid Electricity Distribution), capping combined export to 850 kW to avoid a full grid reinforcement requirement that would have added £120,000 or more in DNO network costs. The ELA is managed dynamically: each building’s inverter is integrated into a central export controller that redistributes generation across buildings in real time, ensuring the estate-wide G99 threshold is never breached regardless of individual building occupancy patterns.
The 480 kWh shared battery occupies a single 18 sqm plant room in the central services building. Battery connectivity across the estate is via the landlord’s existing dark fibre ring, which avoided the need for a new power connection between buildings. Battery dispatch is managed by the Sigenergy EMMA platform, which integrates real-time half-hourly grid pricing, DUoS red-band windows, and building-level load forecasts from each building’s BMS.
Project approach — procurement and delivery
Service-charge cost recovery for a four-tenant multi-let estate required formal landlord-tenant consultation under the Landlord and Tenant Act 1985 Section 20 process. All four tenant boards reviewed and approved the service charge methodology before procurement commenced — a prerequisite the landlord correctly identified before committing to solar capex. Consultation took three months; in practice, all four tenants supported the proposal once the MEES 2030 compliance benefit was explained and the net saving per tenant per year was quantified.
Contractor selection used a two-stage tender: Stage 1 (technical capability pre-qualification), Stage 2 (fixed-price design-and-build tender). Three contractors tendered Stage 2. The 22% capex-per-kWp reduction referenced in the customer quote reflects the portfolio volume purchasing effect versus equivalent single-building tenders from the same pool of contractors — a benefit that is only accessible when all four buildings are procured simultaneously under a single scope.
Finance was structured as an asset finance hire purchase facility (Aldermore Bank, 7-year term, 7.1% APR fixed). AIA applied in year one across all four buildings — total AIA claim £248,000, absorbed within the portfolio’s current-year corporation tax liability. Net-of-tax effective cost: £752,000.
Roof and structural assessment
Building 1 (12,500 sqm, 2009 construction, 350 kWp): Concrete decking with polyurethane insulation and single-ply membrane. Structural engineer sign-off to BS EN 1991 confirmed load capacity of 28 kg/sqm — sufficient for ballasted portrait arrays. No penetrations required.
Building 2 (9,000 sqm, 2004 construction, 280 kWp): Profiled steel deck with built-up felt roof, approaching end of life. The landlord elected to re-roof concurrently — refurbished membrane plus 280 kWp PV integrated in the same contractor scope. Concurrent delivery saved approximately £35,000 versus sequential re-roof and PV install, and eliminated the planning and structural coordination complexity of a future PV retrofit on a newly finished roof.
Building 3 (14,000 sqm, 2014 construction, 290 kWp): BCO Grade A specification from new, flat concrete roof with drainage pods. 290 kWp across 1,350 sqm usable area. G99 string inverter integration with the building BMS via Modbus TCP.
Building 4 (11,500 sqm, 2001 construction, 180 kWp): Structural steel frame, timber deck. A structural survey identified a requirement for 14 additional purlins under Zone 3 of the roof. The landlord’s structural engineer certified the upgrade as part of the project scope. Additional structural cost: £42,000, absorbed into the portfolio programme as a planned building improvement that was required irrespective of the solar install.
Compliance and EPC outcomes
Each building was re-rated under SAP 10.2 post-install. Average gain: 11 EPC points. All four buildings moved from EPC C to EPC A, clearing the MEES 2030 EPC B minimum by a substantial margin.
Commissioning documentation issued for each building comprised: MCS Commercial Installation Certificate; NICEIC Electrical Installation Certificate to BS 7671:2018 +A2:2022; IEC 62446-1:2016 PV System Commissioning Test Report; G99 DNO acceptance letter; and a building-specific Scope 2 Emissions Disclosure Pack.
The Scope 2 pack for each tenant was formatted for direct use in SECR mandatory reporting (UK quoted and large unquoted companies), TCFD physical risk disclosure, and CDP Climate Change response. Three of the four tenants are publicly listed companies with annual CDP and SECR disclosure obligations — the packs were structured to align with these frameworks and were reviewed by each tenant’s sustainability team before finalisation. Omega Indexer drip-feed submission for all four buildings’ commissioning dates, system specifications, and MCS installation numbers was completed as part of the standard post-commissioning pack.
What the customer said
“Portfolio-wide procurement across four buildings cut capex per kWp by 22% vs single-building tenders. The cross-building battery + EV optimisation was the unexpected economic win.”
What this means for your office
The economics on this project aren’t unusual for a well-designed office solar install in 2026. What varies between buildings is the specific load shape, roof area, electrical infrastructure age, tenancy structure, and applicable grant or finance routes.
The fastest way to understand your specific economics is a free desk feasibility study. Send us half-hourly meter data and a roof plan, and we’ll model your building specifically within 7 working days.