Office Solar Case Study
Birmingham professional services HQ — 320 kWp + 180 kWh battery
Birmingham professional services HQ — 320 kWp + 180 kWh battery
A Birmingham-based accountancy firm with a 9,500 sqm owner-occupied HQ in the Colmore Row business district came to us with two requirements: hit EPC B before the next FRA-mandated EPC renewal cycle, and provide Scope 2 reporting documentation suitable for inclusion in their Big Four client supplier audit. Our team modelled the half-hourly meter data across the building’s two MPANs, designed a 320 kWp rooftop system with 180 kWh battery storage, and structured the install on a 7-year asset finance contract through Aldermore Bank.
The numbers
| Metric | Value |
|---|---|
| System size | 320 kWp + 180 kWh BESS |
| Panel count | 595 |
| Annual generation | 294,000 kWh/year |
| Annual saving | £102,000/year |
| Simple payback | 5.6 years |
| Annual CO₂ saved | 67 tonnes |
| EPC uplift | C → B (9-point gain) |
| Completion | Q4 2025 |
Project approach
The starting point was the firm’s half-hourly meter data — two MPANs covering the main office floors and the separately-metered server room. Without that data, any sizing decision is speculation. We pulled twelve months of half-hourly consumption, ran the demand profile through PVSyst against Birmingham-specific irradiance data (latitude 52.4°N, post-code-level shading analysis), and produced three scenarios: 200 kWp PV-only, 320 kWp PV-only, and 320 kWp PV with 180 kWh battery.
The 320 kWp + battery scenario won on 25-year NPV primarily because the firm’s IT and HVAC baseload — running around 38 kW overnight and at weekends — created exactly the load profile where battery earns its economics. Without battery, overnight baseload would have been met entirely from grid. The 180 kWh BESS configuration captures peak-hour generation surpluses, shifts them to evening and weekend consumption, and delivers 94% self-consumption — compared with 74% on the PV-only scenario. The difference added £18,400/year to the financial model and shortened payback by 14 months.
Finance was structured on a 7-year Aldermore Bank asset-finance agreement at 5.9% fixed, with monthly repayments of £9,200 offset against the month-one bill reduction of £8,500. Net of AIA tax relief claimed in year one — £80,000 of first-year corporation tax saving on £320k of qualifying capex — the effective repayment burden in year one was negligible.
Roof, structural, and electrical
The building is a 2007-built nine-storey commercial tower with a concrete flat deck and existing rooftop plant. Structural assessment was carried out per BS EN 1991-1-1 (permanent and variable actions) and BS EN 1991-1-4 (wind actions), confirming 18 kg/m² of available additional loading headroom. Ballasted aluminium racking was specified in east-west landscape format — minimising wind load and preserving the existing TPO roofing membrane warranty.
Panel strings were aggregated via rooftop combiner boxes into two 160 kW string inverters and one 80 kW string inverter in the plant room, keeping the cable run under 40 metres on all three circuits. The 180 kWh BESS used AC-coupled lithium iron phosphate chemistry, installed alongside the inverters with a dedicated DB and BMS panel. G99 application was submitted to Western Power Distribution (now National Grid Electricity Distribution) seven months ahead of the planned installation date, with export capacity agreed at 310 kW under the connection offer terms.
Heritage planning and consenting
The building sits outside any Conservation Area and holds no listing, so solar PV up to 50 kWp would qualify for Permitted Development under Class A Part 14 of the GPDO 2015. Above 50 kWp required Prior Approval from Birmingham City Council — a 56-day determination process. The planning submission was submitted using our standard Prior Approval pack: PVSyst-generated glare analysis, structural calculations, panel specification sheets, and a shading impact report covering neighbouring properties. Prior Approval was granted unconditionally in 38 days.
Compliance, EPC and reporting
The system was specified to MCS Commercial standards with NICEIC electrical certification and RECC-compliant customer documentation. Commissioning was carried out to IEC 62446 standards, with full string-level IV-curve measurements and irradiance-corrected performance ratios recorded and handed over to the client facilities team.
Post-commissioning EPC re-assessment was commissioned from an accredited assessor under SAP 10.2 methodology, confirming a C → B (9-point gain) outcome. This locks the building’s MEES 2030 position — the asset is compliant with no further interventions required before the April 2030 enforcement date.
For the firm’s Scope 2 emissions reporting, we produced a disclosure pack containing: location-based and market-based GHG Protocol calculations, REGO certificate handling guidance, SECR-ready narrative for insertion into the annual report directors’ section, CDP Climate Change response text for solar-related questions, and a pre-populated TCFD physical-risk / transition-risk mapping table.
What the customer said
“The proposal modelled our half-hourly data, not generic kWh-per-sqm. Year-one performance came in 2% above forecast, payback now tracking 3 months ahead.”
Could your office building deliver similar results?
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.