Energy Efficiency in Transport

The transport sector has long understood that fuel efficiency matters. Route planning, driver behaviour, vehicle maintenance, load optimisation. These are not new conversations. What is new is the scale of structural change now underway, as UK businesses face simultaneous pressure to electrify their fleets, reduce their carbon footprint, and keep operating costs under control at a time when energy prices remain volatile.

For many logistics and transport businesses, the reflex response is to focus on the vehicles themselves. But as fleets begin the transition to electric, a second and largely underappreciated challenge is emerging. That is, the energy that powere those vehicles from the depot. 

How that electricity is sourced, what it costs, and how carbon-intensive it is will determine whether fleet electrification delivers on its promise or simply relocates the problem.

For businesses with large depot roofs and rising on-site energy demand, on-site solar generation through a Solar PPA is increasingly being considered alongside fleet electrification as part of a coherent energy strategy, not as a separate initiative.

Why Transport Remains the UK’s Largest Emissions Challenge

The scale of the problem is significant. According to the House of Commons Library, transport was responsible for 29% of total UK greenhouse gas emissions in 2023, making it the single largest emitting sector of the UK economy. Of that, surface transport accounts for the majority: cars and taxis, heavy goods vehicles, and vans, in that order.

For freight specifically, the picture is stubborn. According to the Parliamentary Office of Science and Technology, HGVs account for 19% of surface transport emissions, with vans contributing a further 18%. These vehicles operate on long duty cycles, carry heavy loads, and currently run almost entirely on diesel.

The UK government’s zero-emission vehicle mandate requires 100% of new HGV sales under 26 tonnes to be zero-emission by 2035, and heavier models by 2040. But as of 2024, only 1,271 electric HGVs were operating on UK roads, representing just 0.2% of the total HGV fleet. The transition is coming, but its current pace illustrates how much ground remains to cover.

The Traditional Levers of Transport Energy Efficiency

Before the electrification conversation dominates, it is worth acknowledging that significant efficiency gains remain available through conventional operational improvements. Many transport businesses have implemented some of these measures; fewer have applied them systematically.

• Route and load optimisation is often where the most accessible savings sit. Unnecessary mileage, inefficient load factors, and poor scheduling compound across a fleet quickly. Telematics platforms now make it relatively straightforward to identify patterns and reduce empty or underloaded runs.
• Driver behaviour has a measurable impact on fuel consumption. Based on the Logistics UK’s 2025 industry report, fuel accounts for 27% of the total cost of running a 44-tonne HGV. Smooth acceleration, appropriate speed, and reduced idling can reduce fuel consumption by a meaningful margin without any capital investment.
• Vehicle maintenance and specification also contribute. Under-inflated tyres, poorly serviced engines, and aerodynamically inefficient vehicles all increase fuel demand above what is operationally necessary. For larger fleets, the cumulative effect is material.

These measures matter and should not be abandoned in favour of the electrification conversation. But they are also increasingly well understood, widely implemented, and limited in how far they can take a business toward the emissions reductions that regulatory pressure and supply chain expectations are beginning to demand.

Fleet Electrification and the Energy Problem Nobody Talks About

Electrifying a fleet addresses the tailpipe emissions problem directly. Zero-emission vehicles produce no exhaust emissions at the point of use. For a business trying to reduce its Scope 1 emissions, the logic is sound.

What is discussed far less openly is what happens to depot energy demand when a fleet transitions to electric. A business running fifty diesel vehicles does not currently need to think much about how the fuel powering those vehicles is generated. When those vehicles become electric, that changes entirely. The electricity they run on has to come from somewhere, and if it comes from the grid at commercial rates during peak demand, two problems follow.

The first is cost. Grid electricity for UK businesses currently sits at around 25 to 29p/kWh. Charging a significant fleet at those rates, particularly if vehicles are plugging in at the same time after a shift, can create a substantial new overhead that erodes a portion of the operational savings electrification was supposed to deliver.

The second is carbon. The UK grid has decarbonised considerably in recent years, but it is not a zero-carbon supply. Peak demand periods draw on a mix of generation sources, and the carbon intensity of grid electricity varies by time of day and season. A fleet of EVs charged from the grid is cleaner than a diesel fleet, but it is not as clean as a fleet charged from on-site renewable generation.

Only around 5% of UK warehouses currently have solar installed, despite the fact that logistics and distribution buildings are among the most naturally suited sites in the country for large-scale rooftop solar. The roof space is vast, daytime electricity demand is high and consistent, and the operational profile of a depot aligns well with peak solar generation hours.

How On-Site Solar Supports a More Cost-Effective Fleet Transition

The case for combining fleet electrification with on-site solar generation is not complicated. It comes down to two things: the cost of the electricity going into the vehicles, and its carbon content.

On cost, the difference is significant. While grid electricity sits at 25 to 29p/kWh for commercial customers, on-site solar generation through a Power Purchase Agreement typically delivers electricity at around 5 to 8p/kWh. For a depot with a sizeable fleet to charge, that differential compounds quickly. A modern distribution centre of 10,000 to 50,000 square metres typically consumes between 500,000 and 3,000,000 kWh per year, a figure that will increase as EV charging is added to the load. Reducing the cost per unit across that volume changes the energy economics of the site materially.

On carbon, on-site solar generation is as close to zero-carbon electricity as a business can get without owning a generating asset. Vehicles charged during daylight hours from a rooftop array are running on clean power produced at the point of use. That is a fundamentally different carbon story to vehicles charged from the grid, and it shows up in Scope 2 emissions reporting, in product lifecycle assessments, and increasingly in the sustainability data customers and procurement teams are requesting.

The structural advantage for logistics and transport businesses is straightforward: UK warehouses have over 2.24 billion square feet of roof space in units over 50,000 square feet, the vast majority of which is currently generating nothing. That dormant roof space is a significant energy asset waiting to be used.

A Solar PPA removes the capital barrier. Rather than funding the solar installation outright, the business enters an agreement with an energy provider who funds, installs, and maintains the system. The business buys the electricity generated at a pre-agreed rate below grid cost. The capital that might otherwise have been committed to solar infrastructure stays available for the fleet transition itself, or for core operational investment.

What to Consider When Planning Depot Energy for an Electric Fleet

For businesses beginning to think seriously about this, a few practical considerations are worth working through early.

• Roof condition and size. Logistics and distribution buildings tend to be well suited for solar, with large, relatively unobstructed flat or shallow-pitched roofs. The key variables are structural condition, any existing plant or equipment occupying roof space, and whether the building is owned or leased. Leasehold situations require landlord engagement, which is increasingly common as landlords recognise the asset value of solar-ready buildings.
• Grid connection capacity. This is where businesses are frequently surprised. Adding significant EV charging infrastructure to a depot can require a grid connection upgrade, which is both expensive and slow. Energy UK has noted that installing 50 chargepoints at a large logistics site can cost in the region of £5 million in connection costs alone. On-site solar generation reduces the volume of power that needs to be imported from the grid, which can ease connection constraints and reduce the upgrade requirement.
• Charging profiles and solar generation timing. Daytime solar generation aligns well with depot operations that run day shifts. Businesses where vehicles return and charge during daylight hours will see stronger self-consumption. Fleets that operate primarily overnight present a different profile, where battery storage alongside solar becomes a more relevant consideration.
• Phasing the transition. Fleet electrification rarely happens all at once. Installing solar now, sized to current consumption, locks in a low cost per unit for the long term. As EV charging adds to the depot’s electricity demand over time, the solar array is already in place and generating at a known rate. 

The Wider Transport Efficiency Picture

On-site solar addresses the depot energy challenge, but it operates within a broader transport efficiency strategy rather than replacing one.

Fleet electrification reduces tailpipe emissions and, when combined with lower-carbon depot energy, meaningfully cuts the total carbon footprint of a transport operation. But electrification is not the whole answer for every fleet. Heavy long-haul freight, where battery range and charging time present genuine operational constraints, is likely to require hydrogen or alternative fuel solutions that are still maturing commercially. Businesses planning fleet transitions over the next five to ten years should factor in which parts of their operation are candidates for electrification in the near term and which require a longer horizon.

Route and load efficiency, driver behaviour, and vehicle specification continue to matter regardless of what a vehicle runs on. The operational gains from these measures compound with the energy savings from on-site generation, and they require no capital investment to begin. Modal shift, where possible, is also worth considering. Transferring freight from road to rail where routes and volumes permit reduces emissions substantially, though the operational flexibility constraints of rail freight mean it is not applicable to every business.

The transport businesses making the most coherent progress toward decarbonisation are treating these decisions as a connected system: cleaner vehicles, cleaner energy to power them, more efficient operations, and smarter logistics decisions. On-site solar sits within that system as the infrastructure layer that makes the energy side of that picture work.

Reduce Your Depot’s Energy Costs with Power Zero

A Power Zero Solar PPA provides logistics and transport businesses with a practical, capital-free way to lower depot electricity costs and reduce the carbon intensity of on-site operations. With no upfront investment required, businesses can begin generating clean power from existing roof space while keeping capital available for core fleet and operational priorities.

Use our Commercial Solar PPA Calculator to see what on-site generation could mean for your depot’s energy costs and carbon performance. Or explore our Solar PPA solutions to understand how a fully funded model works in practice.