On-road engine stop/start and parked-cab cooling need separate business cases. One changes how a truck uses fuel while travelling; the other addresses comfort during stationary periods. A saving reported for one system should not be presented as evidence for the other.

What Volvo announced

Volvo Trucks' 4 November 2025 announcement describes an I-Roll engine stop/start function that temporarily stops the engine in suitable driving conditions. The release says activation is above 60 km/h and reports potential additional savings subject to operating conditions. It is not an overnight parking-cooling test.

Divide the vehicle's day into operating states

For a fleet study, record time spent driving, loading, waiting, resting and parked without an occupant. Add the reason the engine runs during stationary periods. Some engine operation may support a required vehicle function, while other operation may be primarily for cabin comfort. Treating all stationary engine hours as avoidable can overstate the opportunity.

Then identify the subset of those hours a proposed cooling system can actually replace. Match that period with the system's usable energy, cooling capability and operating limits. If the battery runs out before the rest period ends, count the remaining time separately.

Use a transparent calculation

A planning model can use avoided cooling-related engine hours multiplied by measured fuel consumption during those hours. Subtract the cost of replenishing energy and the incremental maintenance costs of the alternative. Keep equipment purchase and installation as separate investment inputs.

The model should show where each input came from. A telematics record, a measured idle test and an assumed fuel price carry different levels of confidence. Include a range for uncertain inputs so that the decision does not depend on one optimistic figure.

Check the driver's experience

Reduced engine hours are useful only if the proposed arrangement meets the required cabin conditions. Record the temperature at the bunk, interruptions and the driver's ability to use the controls during a trial. Avoid treating a switched-off engine as proof of a successful comfort outcome.

Fleet buyers can consider driving-efficiency improvements and parking cooling as complementary projects. Give each its own baseline, test and results. That approach helps finance and operations understand what changed and prevents a vehicle manufacturer's road-test claim from becoming an unsupported promise about an aftermarket air conditioner.

Next step

Compare the available configurations in the Vethy product catalog, then request the current model-specific documentation before selecting a unit.

Sources and method