A distribution business tired of guessing at its energy bill
Sun Mark Ltd runs a busy operation in Greenford, Middlesex. A working site that draws real power, day in day out, to keep things moving. Energy prices had been climbing for years, and every rise landed straight on the running costs. Sun Mark wanted to stop being at the mercy of the market. They wanted their bills steadier and lower, and they wanted the sustainability side to show up as real action, not a line in a report. Above them sat the obvious answer, and most of it was going to waste.
A big flat roof, doing nothing
Plenty of commercial sites have acres of flat roof and never think to use it. That was the opening here. The task wasn't a tricky roof, it was making the most of a good one. Size the system to the site's real demand, lay it out so a shallow 5° south-facing flat roof pulls its full weight, and fit the lot without getting in the way of a live operation. Get the sizing wrong and you either waste roof space or throw away generation the business could have used.
A 51.6 kWp system, laid out to fill the roof
We ran the whole job end to end, from budgeting and design through to install and commissioning. The layout was built to make the most of the south-facing flat roof, on a mounting system engineered for durability and safety, and fully compliant with UK electrical and building rules. The total came to £54,000, with the design left open to add battery storage later.
- 120 × Trina Vertex S 430W panels (51.6 kWp total), picked for efficiency and long-term reliability
- 1 × Solis 50kW 3-phase inverter
- Laid out across a south-facing flat roof at a 5° pitch, on a durable mounting system
- Installed with minimal interference to day-to-day operations, and future-ready for battery
More than 40% of the site's power, made on its own roof
That flat roof now generates 55,000 to 58,000 kWh a year. That covers more than 40% of everything the site uses. In cash it works out at roughly £9,600 to £10,400 off the bill every year, close to £867 a month, and £240,000 to £260,000 across the system's life, with the full £54,000 paid back in about five years. After that the roof keeps earning, on space that used to sit empty.
Generation and saving figures on this page are estimates, modelled from the system size and a typical UK yield. They are not meter readings. Your own figures depend on your roof, your usage and the weather in any given year, and we confirm them from a real assessment rather than a model.
