Maidstone Borough Council Depot

The Depot is Maidstone Borough Council’s operational centre for parks, waste and environmental services. The council wanted to cut the site’s electricity costs as part of its goal of reaching net zero across its own operations, and the depot’s large roof made it a good place to start.

We modelled the system against the depot’s half-hourly electricity data, then installed 264 panels across the main roof. A 96kWh Sigenergy battery, housed in a secure enclosure outside the building, stores surplus solar for use later in the day.

Fire safety

We chose SolarEdge inverters and power optimisers for the safety they bring to a busy working site. The optimisers give panel-level monitoring, so a fault shows up straight away, and SolarEdge’s SafeDC feature drops each optimiser’s output to a safe 1V whenever the system shuts down. Without it, the cabling on a roof this size can carry several hundred volts DC even when the inverters are off.

We integrated the system with the depot’s fire alarm and generator. If the fire alarm goes off or the generator is switched on, the solar shuts down automatically and the roof cabling drops to safe mode, so firefighters and site staff aren’t working near live high-voltage DC.

Results

The system was commissioned in January 2026. Over its first summer, the council reported that electricity costs from June to August had fallen by almost 50% compared with the same months the year before, a saving of more than £3,500.

• System capacity: 169 kWp
• Modules: 264 × LONGi 640W
• Inverters: SolarEdge three-phase, with 133 power optimisers and SafeDC
• Safety integration: automatic shutdown on fire alarm or generator start
• Battery storage: 96 kWh (8 × Sigenergy SigenStack 12kWh), with a Sigenergy 50kW hybrid inverter
• Annual generation: around 154 MWh/yr (modelled)
• Self-sufficiency: around 57% of the depot’s electricity (modelled)
• CO₂ saved: around 58,000 kg/yr (modelled)

Read Maidstone Borough Council’s post about the results.