Office Solar Case Study
Bristol tech HQ — 420 kWp + workplace EV charging + battery
Bristol tech HQ — 420 kWp + workplace EV charging + battery
A Series-B software company occupying 6,800 sqm of Grade A office space at Bristol’s Temple Quarter wanted to support their newly-published SBTi 1.5°C target and differentiate engineering recruitment from London-based competitors. We designed a 420 kWp rooftop PV system, 200 kWh BESS, and 18 × 22 kW workplace EV chargers funded in part by OZEV Workplace Charging Scheme grants. Total project value £498k, structured on cash purchase with £124k of year-one AIA tax saving.
The numbers
| Metric | Value |
|---|---|
| System size | 420 kWp PV + 200 kWh battery + 18 × 22 kW EV chargers |
| Panel count | 780 |
| Annual generation | 386,000 kWh/year |
| Annual saving | £124,000/year (PV) + £41,000 (EV revenue) |
| Simple payback | 5.2 years |
| Annual CO₂ saved | 88 tonnes |
| EPC uplift | C → A (15-point gain) |
| Completion | Q3 2025 |
Project approach
The system was designed as three integrated elements: rooftop PV, battery storage, and workplace EV charging. The integration matters because the economics of each component improve when they work together — solar charges the building during the day, battery stores surplus for evening EV charging, and EV chargers monetise surplus generation that would otherwise export at SEG tariff rates.
Half-hourly meter data showed the typical tech-company demand curve: sustained IT and server-room baseload around 65 kW throughout the 24-hour cycle, with HVAC peaks 09:00-18:00 adding a further 30-50 kW. This high overnight baseload made battery storage particularly valuable — the 200 kWh BESS captures midday solar surplus and discharges it against the overnight baseload, lifting self-consumption from an estimated 68% (PV-only) to 91% (PV+battery). The EV chargers, running primarily 07:00-09:00 and 17:00-19:00, add a further demand that the battery pre-positions for using morning solar and overnight charge.
The 18 × 22 kW EV chargers qualified for OZEV Workplace Charging Scheme (WCS) grants of £350 per socket — a total of £6,300 offset against the charger capex of £112,000. WCS grant applications were prepared and submitted as part of the overall project proposal, with approval confirmed before the installation programme commenced.
Finance for the full £498k project was structured as cash purchase, maximising AIA tax relief: £124,500 claimed in year one at 25% corporation tax rate on the £498k total capex (all qualifying as plant and machinery under HMRC CG89360 guidance on solar PV and EV infrastructure). The net effective capex after year-one tax relief was £373,500.
Roof, structural, and electrical
The Grade A office building at Bristol’s Temple Quarter has a large flat concrete roof deck with existing plant room access. Structural assessment per BS EN 1991-1-1 and BS EN 1991-1-4 confirmed 22 kg/m² of available headroom above existing dead and live loads. East-west landscape arrays were specified in lightweight aluminium frames, ballasted to avoid roof penetration and preserve the existing EPDM membrane warranty.
The 420 kW DC array was aggregated into four string inverters totalling 380 kW AC output, derated to ensure G99 export limits (320 kW export cap under the connection offer) were respected at all times, with the 200 kWh BESS acting as a behind-the-meter buffer rather than grid-export device. Western Power Distribution (now National Grid Electricity Distribution) G99 application was submitted simultaneously with the planning application, achieving connection offer in 14 weeks — within the fast-track timeline associated with export-limited applications below 1 MW.
EV charger infrastructure required a new 400A supply from the main switchroom to the car park, with a dedicated DB panel for the 18-charger cluster. All chargers are smart-enabled, managed by a cloud-based load-management system that prioritises EV charging from battery and solar rather than grid import where possible.
Compliance, EPC and reporting
The system was installed to MCS Commercial standards with NICEIC electrical certification across both the PV/BESS and EV charger elements. EV charger installation was additionally certified by OLEV-approved electricians under the Domestic and Non-Domestic WCS scheme requirements. Commissioning of the PV and BESS followed IEC 62446; EV charger commissioning followed EVIOS network protocols with load-management integration tested under ISO 15118 for smart charging capability.
Post-commissioning EPC re-assessment confirmed the C → A uplift (15-point gain) — the exceptional uplift reflecting both the scale of the PV system relative to floor area and the Passivhaus-quality fabric installed during the 2024 fit-out. The A-rating placed the building in the top 2% of commercial office EPC scores nationally, making it a material differentiator in lease negotiations and insurance rating.
For SBTi reporting, we provided full Scope 2 documentation (location-based and market-based), REGO certificate handling guidance, and a draft Science-Based Targets pathway statement confirming the solar installation’s contribution toward the firm’s 1.5°C operational emissions commitment.
What the customer said
“The integrated solar + battery + workplace EV proposition won us three engineering hires in the first quarter — recruits explicitly cited workplace charging as a deciding factor.”
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.