An oversized solar array and battery storage cut grid dependency by around 80%.

A private landlord in North Wales asked Warmer to reduce running costs and grid reliance across a 12-flat residential block, and to strengthen the building’s long-term sustainability credentials.

The system we designed and installed:

• 47 high-efficiency 540W solar PV panels, giving 25.3kWp of installed capacity
• 30kWh battery energy storage system
• Export tariff on surplus generation

Rather than matching the array to daytime demand alone, we deliberately oversized it to maximise generation across the year. Surplus daytime electricity charges the battery for use during the evening peak, and once the battery and building demand are met, the remainder is exported to the grid for additional income.

The results:

• Around an 80% reduction in grid electricity dependency
• Summer electricity bills effectively eliminated, with generation exceeding the building’s consumption
• Energy-positive operation during the summer months, with export income offsetting remaining costs
• More than 20MWh of renewable electricity generated each year, with a corresponding cut in the building’s carbon footprint

For the landlord, the outcome is lower, more predictable running costs, reduced exposure to energy price volatility and a more attractive building for tenants. The same design approach applies to offices, warehouses and other commercial and multi-occupancy buildings with suitable roof space.