Warehouses are the best commercial buildings for solar — large flat roofs, high daytime electricity use, and long-term occupancy. But what do the numbers actually look like? We break down three real UK installations with verified costs, savings, and payback data.

Why Do Warehouses Get the Best Solar ROI?

Warehouses consistently outperform other commercial buildings on solar ROI for four reasons:

• Large unobstructed roofs: 1,000-10,000m² of flat, shadow-free space allows optimal panel placement. A 1,000m² roof fits 100-140kW of solar capacity.
• Daytime electricity alignment: Warehouses operate during peak solar hours. Lighting, HVAC, refrigeration, forklifts, and conveyors all draw power when panels generate most.
• High self-consumption: 60-75% of generated electricity is used on-site (vs 30-40% for domestic). Every kWh consumed on-site saves 22p instead of earning 3-15p from export.
• Scale economies: Larger systems cost less per kW. A 500kW system costs £800/kW vs £1,200/kW for a 50kW system.

Case Study 1: Gregory Distribution — 1,608kW Across 4 Depots

Gregory Distribution is a multi-site logistics operator that installed solar across four depot locations. The 1,608kW combined system generates over £250,000 in annual savings and cuts carbon emissions by 324.8 tonnes per year.

Why it works: Logistics depots have constant daytime loads — cold storage, sorting equipment, lighting across large floor areas, and EV charging for delivery fleets. Gregory's depots consume electricity during exactly the hours solar panels produce it, driving self-consumption rates above 70%.

The multi-site advantage: By consolidating their solar strategy across four depots, Gregory achieved lower per-kW costs through bulk procurement and a single project management overhead. They also met customer sustainability requirements — increasingly a prerequisite for logistics contracts.

Case Study 2: Dagenham Warehouse — 500kW, 4.2-Year Payback

This East London distribution centre installed a 500kW rooftop system sized to match 75% of daytime electricity consumption. The system was deliberately undersized relative to roof capacity to minimise grid export and maximise self-consumption value.

The sizing decision: The Dagenham roof could have accommodated 700kW+, but the installer recommended 500kW based on the building's load profile. Self-consumed electricity saves 22p/kWh (the avoided grid purchase cost), while exported electricity earns only 3-15p/kWh. By sizing to maximise self-consumption, the 500kW system delivers better ROI than a larger system would.

Financial breakdown: At an estimated system cost of £400,000 and £85,000 annual savings, the simple payback is 4.2 years. After Enhanced Capital Allowances (£100,000 tax relief at 25% corporation tax rate), the net cost drops to £300,000 and effective payback to approximately 3.5 years.

Case Study 3: Westbrook Industrial, Warrington — 21kW, 2.5-Year Payback

Westbrook demonstrates that warehouse solar is not just for large logistics operators. This small industrial unit installed a modest 21kW system that covers over 40% of its electricity needs, paying back in just 2.5 years.

Why small systems can outperform: The 2.5-year payback is faster than the larger installations because small industrial units often have very high self-consumption rates. A 21kW system on a unit with constant machinery loads (CNC, compressors, welding) means nearly every kWh is consumed on-site at the full avoided grid rate of 22p/kWh.

The lesson: You don't need a 5,000m² roof to benefit from warehouse solar. Even units with 150-300m² of roof space can install 15-30kW systems that deliver strong returns. The key factor is daytime electricity demand, not roof size.

How Do These Case Studies Compare?

The pattern across all three case studies is clear: warehouse solar delivers strong returns regardless of scale. The smallest system (21kW) achieved the fastest payback because of near-100% self-consumption. The largest (1,608kW) delivered the highest absolute savings. The mid-range Dagenham installation shows the most common scenario for UK warehouses.

What Does a Typical 500kW Warehouse Solar ROI Look Like?

A 500kW system on a 5,000m² warehouse roof is a common configuration for UK distribution centres. Based on South England irradiance of approximately 950 kWh/kWp, the financial model breaks down as follows:

Assumptions: South England irradiance (~950 kWh/kWp), 70% self-consumption, grid rate 22p/kWh, SEG export rate 15p/kWh. Panel degradation of 0.5%/year not included in simple payback but factored into 25-year total.

What Factors Affect Warehouse Solar ROI?

Four factors determine whether your warehouse solar ROI lands at the high or low end of the range:

• Self-consumption rate (biggest impact): Every kWh consumed on-site saves 22p. Every kWh exported earns 3-15p. A warehouse running 7am-7pm with refrigeration gets 70-80% self-consumption. A warehouse running one shift gets 50-60%.
• System sizing: Oversizing leads to excess export at low rates. Undersizing leaves savings on the table. The optimal system matches 70-80% of peak daytime demand.
• Electricity tariff: Higher grid electricity costs mean higher savings. Warehouses on 25p/kWh tariffs see faster payback than those on 18p/kWh.
• Location: South England generates ~950 kWh/kWp/year. Scotland generates ~800 kWh/kWp/year — roughly 15% less output, extending payback by 6-12 months.

What If You Don't Have the Capital?

If £40,000-£400,000 upfront is not feasible, a Power Purchase Agreement (PPA) lets you get warehouse solar installed at £0 upfront. A third-party investor owns and maintains the system; you buy the electricity at 8-14p/kWh — 30-50% below grid rates.

The trade-off is lower total savings. Over 25 years, buying outright delivers approximately 50-80% more total savings than a PPA because the PPA provider takes a margin. You also miss out on Enhanced Capital Allowances tax relief. But if the alternative is no solar at all, a PPA still delivers meaningful bill reduction from day one.

Warehouse Solar ROI FAQs