A 500 kW warehouse solar system is the entry size for serious distribution centre and large fulfilment installs. With 925 panels covering 3,000-4,500 sqm of roof, the system fits 100,000-150,000 sqft buildings. The £375-475k capex sits at the AIA cap (£1m per company per tax year) so most owner-occupiers fully expense capex year 1.
Typical 500 kW system specification
Capacity: 500 kW. Panels: 925 modules at 540W. Roof area: 3,000-4,500 sqm usable. Inverters: 5-8 string inverters or central inverters. Annual generation: 460,000 kWh. Capex: £375-475k installed. AIA tax shield: £94-119k year 1. Payback: 4.5-5.5 years simple.
When 500 kW is the right size
Distribution centres 100,000-150,000 sqft. Mid-size retailer RDCs. Large fulfilment centres. Cold storage facilities (small-to-mid scale). Mid-size manufacturing with continuous process load.
Economics worked example
500 kW install on a 130,000 sqft DC: capex £425k. AIA tax shield year 1: £106k. Annual generation 460,000 kWh. At 80% self-consumption and 22p/kWh: £81k/yr saving. SEG export: £10k/yr. Total annual benefit £91k. Simple payback 4.7 years. After-tax cash 3.5 years. 25-year IRR 22%.
Common questions about 500 kw system
Is 500 kW the sweet spot for warehouse solar?
For many distribution centres, yes. The £375-475k capex sits comfortably within AIA cap (full year-1 tax expensing). Per-kW economics improve materially vs sub-300 kW. PPA financing also becomes viable at this scale (typically 250-500 kW minimum for PPA structuring).