Spirit Energy's 695 kWp installation at Philip Dennis Foodservice in Oxfordshire, split across a distribution warehouse and a cold store, is projected to save the business more than £85,000 a year on electricity with a five year payback and an IRR above 23%. Cold storage suits solar unusually well because refrigeration runs continuously, so almost every unit generated is consumed on site rather than exported at a lower rate. Self-consumption, not roof orientation or panel efficiency, is what drives commercial solar returns.
The value of a solar system to a business comes down to a single comparison: what a generated unit is worth when you use it, against what it is worth when you sell it. A unit consumed on site avoids the full import price, including the non-commodity charges that now make up a large share of a commercial bill. A unit exported earns whatever the export agreement pays, which is materially less.
An office block generates most of its solar on summer afternoons and at weekends, when the building is half empty. Much of that output leaves the site at the lower rate.
A cold store has no such gap. Compressors cycle through the night, through weekends, and through the Christmas shutdown, because product temperature does not observe opening hours. Refrigeration is the dominant electricity load on the site and it never stops.
That is the whole argument in one line: the building with the flattest, most relentless load profile in UK commercial property is also the building where solar is worth the most per kWh generated.
It matches on two separate cycles, which is unusual.
Seasonally, heat ingress through a cold store envelope and through its dock doors is a function of the temperature difference between outside air and the set point. A store held at minus 20 degrees works measurably harder in August than in January. Solar output in southern England peaks across the same months, so the extra cooling load and the extra generation arrive together.
Daily, ambient temperature peaks in the early to mid afternoon, close to the daily generation peak, and inside the same window where distribution network charges are at their highest.
Overnight load continues, which is where commercial battery storage earns its place. Storing midday surplus and discharging it into evening compressor demand shifts generation into the most expensive tariff periods rather than exporting it.
Philip Dennis Foodservice runs a two site facility in Oxfordshire: a standard distribution warehouse and a cold store, with the cold store accounting for the majority of the site's electricity consumption.
Spirit Energy covered both roofs. The design came to 695 kWp in total, 367 kWp on the warehouse and 328 kWp on the cold store, using 1,636 Trina 425W panels feeding six Solis 100 kW inverters. Estimated annual generation is 720,000 kWh.
The financial outcome:
The system also generates more than the business needs at times, and the surplus is sold back to the grid at a fixed rate. That is worth stating plainly, because the assumption that a cold store is simply too hungry for rooftop solar to matter does not survive contact with a properly sized array on a large roof.
Environmentally, the installation offsets 143,850 kg of CO2 a year, and 2,877 tonnes across 20 years. Philip Dennis financed it through a solar power purchase agreement with no deposit, so the savings started without capital leaving the business.
Cold stores are built from composite insulated panels, and that changes the installation before a single panel goes up. The mounting approach has to preserve the insulation envelope, which usually means non-penetrative or ballasted systems and a full structural survey to confirm the roof can carry the additional load and the wind uplift.
There is also an advantage that gets overlooked. Cold store roofs carry few or no rooflights, because a rooflight is a thermal weak point and a condensation risk in a temperature controlled building. An ambient warehouse roof of the same footprint is typically broken up by rooflight bands and service penetrations. The cold store gives you more uninterrupted, usable area per square metre of roof.
One practical point from the Philip Dennis project: the client was having the roof replaced at the same time, and Spirit Energy worked alongside the roofing contractor to deliver both together. If a cold store roof is approaching replacement, that is the moment to design the solar, not five years afterwards.
Solar arrays are almost never matched one to one with inverter capacity. A system is usually designed with more DC capacity on the roof than the inverters behind it can pass through, typically somewhere between 1.1 and 1.3 times. Where a cold store differs is in how that ratio should be set.
The reason for the imbalance is winter performance. In low irradiance conditions an array will never come close to its rated output, and a smaller inverter means the incoming DC represents a higher fraction of that inverter's capacity, which keeps it in a more efficient part of its operating curve for more of the day. The cost is a small amount of energy lost at the top end on the handful of brightest summer days, when generation briefly exceeds what the inverter can pass.
On a site with a flat 24/7 baseload, that trade is worth making, because every additional winter kWh is consumed on site at the full import price rather than exported. On a building that sits empty in December, the calculation is different, and the same ratio would be the wrong choice.
This is a design decision rather than a product choice. It does not appear on a specification sheet and it is the sort of thing that gets missed when system design is outsourced.
Cold storage is one of the most electricity-intensive activities in UK commercial property, and that makes it one of the hardest parts of a business to decarbonise on paper. Refrigeration cannot be switched off, reduced during peak periods without careful planning, or moved elsewhere.
On-site generation is one of the few interventions that reduces the actual electricity a site draws from the grid rather than changing how that electricity is described. A renewable tariff can be switched at the next contract renewal. A rooftop array stays on the roof for 25 years or more.
That distinction matters more each year, as supermarket buyers and large food service customers push emissions requirements down into their supply chains. Carbon performance is increasingly part of the tender rather than an appendix to it, and an installed generating asset is a straightforward thing to evidence.
Spirit Energy has been designing and installing across the UK since 2010, with more than 6,000 installations completed and all design carried out in-house. For a cold store, the appeal is straightforward: a fixed operating cost becomes an owned asset that keeps working for decades.