TechHub Office: 200kWp BREEAM Outstanding London

The site

A 1990s-built mid-rise office in central London, 18,500 m² floor area, undergoing a BREEAM Outstanding refurbishment to attract a new prime tenant. The original roof was largely free of plant after the building’s HVAC was repositioned to the north elevation during refurb.

The brief

The developer wanted on-site renewable generation as a BREEAM Outstanding credit-earning measure. A minimum of 14% of regulated annual energy demand needed to come from on-site renewables to clear the BREEAM threshold. The funding case combined certification value (faster letting, rental premium) with pure energy economics.

What we did

Two-array configuration to maximise useful roof area:

• 140 kWp on the main upper roof
• 60 kWp on the lower podium roof (different orientation, secondary array)
• 100 kWh battery in the basement plant room to firm self-consumption against the office evening peak

The financial case combined direct energy savings (£18,500/year) with certification value (estimated at 1.4% rental premium, equivalent to ~£12,000/year of rental uplift on the building). Total effective annual benefit £30,500.

The numbers

• Headline capex: £180,000 (PV) + £40,000 (battery) = £220,000
• Full Expensing relief: £55,000
• SEG export revenue (year 1): £4,200
• Net cost: £165,000
• Annual energy savings: £18,500
• Annual certification-value uplift: ~£12,000
• Combined effective annual benefit: £30,500
• Payback: 5.0 years

What happened

Commissioned November 2024 as part of the wider refurbishment programme. Building achieved BREEAM Outstanding rating in early 2025. Pre-letting completed before practical completion at a 1.6% premium against the asset manager’s underwriting case.

Why it worked

The combined energy + certification value case got the project to a credible payback. Pure energy economics on this site would have produced a 9.5-year payback — too long for the developer’s hurdle. The certification-value contribution is what made the case work.