How to Reduce Transport Refrigeration Unit Emissions

Why TRU Emissions Matter

Although TRUs are small compared to the vehicle they sit on, their impact is large. They run for long periods, often while vehicles wait in depots, load, unload or queue.

TRU impacts include:

• Fuel use — 10–15% of temperature-controlled fleet fuel can arise from cooling alone
• Scope 1 and Net Zero targets — especially significant in heavy-duty fleets
• Air quality — affecting both staff and communities where fleets operate

The Quickest Win: Plugging In Diesel TRUs

Most diesel TRUs already support electric standby. Running them from the grid while in depot environments is the fastest and simplest way to cut emissions — no vehicle changes required.

A typical site using 7 MWh of electricity per year for TRU plug-in can save approximately:

• 3,000 litres of diesel
• £1,800 in fuel costs
• 6.2 tCO₂e (tonnes of CO₂ equivalent) annually

Some sites in our portfolio consume closer to 11.5 MWh per year, cutting nearly 10 tCO₂e per year and reducing the fuel bill by more than £3k per year for every plug installed.

Why Fleets Struggle to Capture Plug-In Savings

Despite the clear benefits, common barriers prevent many fleets from realising plug-in savings:

• Uncertain ROI — few sites accurately measure consumption, making it hard to justify investment
• Low compliance — drivers may not be aware of the benefits or remember to plug in
• Power constraints — existing grid connections may not support additional electrical loads
• Infrastructure reliability — faulty sockets and poor maintenance undermine plug-in programs

Our TRU Fuel Saver system addresses these barriers with smart plugs and a digital platform that tracks both plug status and usage in real time. This improves equipment uptime, enables clear ROI measurement, and manages power to overcome site constraints.

The Technology Landscape

Beyond plug-in, several alternative technologies offer lower-emission refrigeration. Each comes with advantages and constraints.

Electric TRUs (eTRUs)

A rapidly improving option with major benefits:

• Far lower running costs (electricity vs diesel)
• Much lower CO₂ intensity
• Potential for further efficiency improvements via solar or advanced vapour compression

Today there is a significant cost premium of between £20k and £30k that can be recovered in some duty cycles over the asset's life.

Biofuels

Simple to adopt and compatible with existing hardware, but constrained by limited feedstocks and variable emissions performance.

Hydrogen

Zero-tailpipe emissions and potentially good performance, but low technology maturity and high fuel costs make it a very expensive choice today.

Cryogenics

Solutions involving liquid nitrogen or CO₂ offer quiet, clean operation but require specialised refuelling infrastructure. Operating costs can be high depending on local industrial gas supply conditions.

Are Electric TRUs Cost-Effective?

Yes — particularly for fleets running 12+ shifts per week. Key variables include utilisation, diesel price, and eTRU hardware costs.

Using typical cost and efficiency assumptions, electric TRUs can deliver meaningful lifetime savings, especially for higher-utilisation fleets. Payback times shorten as:

• Utilisation increases
• Diesel prices rise
• eTRU hardware costs fall
• Solar or efficiency improvements are added

Duty Cycles Shape Economics

TRU energy consumption varies widely depending on temperature set points, insulation performance, ambient weather, door openings, and loading/unloading behaviours.

We modelled a comparison of electric and diesel TRUs using the following assumptions:

• Diesel TRU cost: £18–21k
• Electric TRU cost: £40–50k
• Diesel price: £1.10 per litre
• Electricity cost: £0.22 per kWh

Fuel use was modelled using test cycles and results from the Zemo Partnership HGV Auxiliary Engines: Baseline auxTRU testing and modelling of UK impacts.

At default assumptions, payback varies dramatically with utilisation:

	Single Shift – 7 days/week		Triple Shift – 7 days/week
	Diesel Use (L/yr)	eTRU Payback	Diesel Use (L/yr)	eTRU Payback
Chilled	1,628	13.5 years	4,883	4.5 years
Frozen	2,753	9.3 years	8,258	3.1 years
Multi-Temp	3,558	8 years	10,675	2.7 years

These results are very sensitive to operating and performance assumptions.

A Practical Roadmap for Reducing TRU Emissions

Short Term

• Plug in existing TRUs at depot
• Use smart plugs to monitor and manage consumption
• Analyse duty cycles to identify high-impact opportunities
• Deploy biofuels where practical

Medium Term

• Deploy eTRUs for high-utilisation routes
• Expand electrical infrastructure
• Integrate solar or advanced cooling technologies

Long Term

• Transition to full electrification
• Monitor emerging hydrogen and cryogenic solutions

Conclusion

TRU emissions represent one of the biggest untapped decarbonisation opportunities in the cold chain. Fleets that take a structured, data-led approach can achieve:

• Immediate reductions in diesel use
• Significant operating cost savings
• Measurable progress toward net zero

Case Study

FPS TRU Fuel Saver Cuts Transport Refrigeration Emissions for Waitrose

To realise its TRU fuel and emission saving goals, Waitrose needed to overcome several challenges: * Building the business case for capital investment in plug infrastructure. *...

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