Flat-roof solar case studies
We label these as modelled scenarios rather than pass off stock testimonials as real clients. Each is built from realistic figures for its building type and shows the engineering behind the result.
520 kWp ballasted east-west array on a distribution warehouse
A distribution warehouse on a trading estate with a large single-ply flat roof and a strong daytime load from lighting, chargers and refrigeration. The owner wanted to cut a rising electricity bill and meet a customer-driven Scope 2 target without piercing the roof membrane. Representative, modelled scenario, not a named client.
- System
- 520 kWp ballasted, penetration-free dual east-west array on protective slip-sheets, tilted 10 degrees
- Roof area
- 4,600 m²
- Annual generation
- About 470,000 kWh
- Self-consumption
- Around 75% used on site, surplus exported under the Smart Export Guarantee
- CO₂ saved
- About 95 tonnes/yr
- Payback
- About 6 years
Outcome: Wind-uplift designed to BS EN 1991-1-4 with heavier perimeter and corner ballast; a structural engineer confirmed the deck's residual capacity for the array before design. Penetration-free mounting kept the single-ply guarantee intact. East-west layout fitted roughly 40% more capacity onto the roof than a south-only layout and matched the all-day operation, lifting self-consumption.
180 kWp roof-renewal-then-solar on a manufacturing unit
A manufacturing unit with a continuous daytime process load whose owner wanted rooftop solar, but whose 20-year-old built-up felt roof ponded in places and was near the end of its life. Installing an array first would have meant lifting it to re-roof within a few years. Representative, modelled scenario, not a named client.
- System
- 180 kWp array installed after the felt roof was renewed to a new single-ply warm deck; mounting designed for the new membrane
- Roof area
- 1,700 m²
- Annual generation
- About 162,000 kWh
- Self-consumption
- Around 85% used on site by the process load
- CO₂ saved
- About 33 tonnes/yr
- Payback
- About 5.5 on the solar element years
Outcome: The roof survey flagged the life-expired membrane before any array was committed, so the roofing works were coordinated first and the array designed for the new roof. Very high self-consumption from the steady process load gave the fastest payback of any sector. The owner paid to fit the panels once, onto a roof with a full service life ahead of it.
6 kWp lightweight array on a flat-roofed home extension
A homeowner with a modern flat-roofed rear extension and no usable pitched roof wanted to cut their electricity bill and charge an EV. The flat felt roof had limited load headroom, so a full ballasted array was not appropriate. Representative, modelled scenario, not a named client.
- System
- 6 kWp lightweight, low-ballast array tilted 12 degrees, paired with a 5 kWh battery, MCS-certified
- Roof area
- 40 m²
- Annual generation
- About 5,300 kWh
- Self-consumption
- Lifted from around 35% to about 65% with the battery
- CO₂ saved
- About 1.1 tonnes/yr
- Payback
- About 9 years
Outcome: A lightweight design kept the load within the extension deck's capacity while preserving the felt membrane. The battery roughly doubled the share of generation used in the home, given lower daytime occupancy. The install qualified for the 0% VAT rate on domestic energy-saving materials (in place until 31 March 2027) and was notified to the DNO under G98.
Get a modelled proposal for your roof
Responds within one working day
- 1. Free desk feasibility from your meter data and roof, no obligation.
- 2. Site survey and a fixed-price proposal, itemised in writing.
- 3. Install and aftercare by MCS-certified engineers.
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