Idling is fuel spent to go nowhere. The US Department of Energy's Alternative Fuels Data Center estimates that American vehicles burn more than six billion gallons of fuel a year without moving. For an individual fleet the numbers are smaller, but they share a trait: nobody sees them, because idle fuel is buried inside the fuel bill.
This article is about making that cost visible, and then reducing the part of it that is waste.
Measure first: what "idle" means in your data
Most telematics units report idling as time with the engine running and the vehicle stationary. Before building a business case on that number, check three things:
- The threshold. Some platforms count idling from the first second; others only after one, three or five minutes. A two-minute stop at a traffic light should not be counted as waste.
- Power take-off. A refrigerated van, a tipper or a crane truck may need the engine running to work. Separate PTO time from idle time or you will punish the wrong drivers.
- Fuel rate. Where the device reads engine data, it can report fuel actually used while idling. That is far better than an assumed litres-per-hour figure, because idle consumption varies a lot by engine and by load, such as air conditioning.
If your platform cannot separate these, the telematics data you already pay for may still contain the raw engine signals; it is worth asking the vendor.
Averages hide the distribution. Idle time is usually concentrated: a small group of vehicles, routes or habits accounts for most of it.
From hours to money: a worked example
Take a hypothetical fleet of 40 light commercial vans. The telematics report shows an average of 50 minutes of idling per van per working day, after removing stops under two minutes.
For the arithmetic, assume each van burns about 1 litre of fuel per idle hour — replace this with your own measured rate — and that fuel costs 1.50 per litre.
| Item | Calculation | Result |
|---|---|---|
| Idle hours per van per day | 50 min ÷ 60 | 0.83 h |
| Idle hours per van per year | 0.83 × 230 working days | ~192 h |
| Fuel per van per year | 192 h × 1 L/h | ~192 L |
| Cost per van per year | 192 L × 1.50 | ~288 |
| Fleet cost per year | 288 × 40 vans | ~11,500 |
That is fuel alone. Idling also accumulates engine hours without distance, which brings forward oil changes and some maintenance on vehicles serviced by engine hours, and adds wear on components such as injectors and exhaust after-treatment. Include it in your cost per mile model rather than leaving it in the general fuel line.
Necessary idling and wasteful idling
Not all idling is waste, and a programme that treats it all the same will lose drivers' trust immediately.
Often necessary: powering refrigeration or equipment, keeping a cab safe in extreme heat or cold, short stops in traffic, waiting in a queue at a busy dock that moves every minute.
Usually waste: warming up the engine for several minutes in mild weather, leaving the engine on during a delivery, idling during breaks, running the engine while completing paperwork.
The line depends on climate, vehicle and task. Set it with drivers, in writing, and apply it consistently.
Reduction levers, cheapest first
- Show drivers their own numbers. A weekly idle summary per driver, compared with peers on similar routes, is often enough to cut the worst habits. It works best as part of a broader driver behaviour scoring approach rather than as a stand-alone league table.
- Fix the reasons people idle. If drivers idle to keep the cab warm while they do paperwork, a faster proof-of-delivery flow removes the reason.
- Use the vehicle's own features. Many modern vans have automatic stop-start; check it has not been disabled as a habit.
- Plan better stops. Long waits at customer sites are partly a planning problem — time windows and dock booking reduce queuing.
- Consider equipment for special cases. Auxiliary heaters or battery-powered refrigeration can remove the need to idle where the task genuinely requires power. These need their own payback calculation.
Building the business case
The reduction target should be realistic. Removing all idling is neither possible nor desirable; halving the wasteful part is a common and achievable goal in many fleets.
In the worked example above, cutting idle time from 50 to 30 minutes per day would save around 40% of that idle fuel cost, before counting maintenance effects — a modest but real saving that needs little investment beyond reporting and conversation. It also belongs in your wider fuel cost management plan and, for fleets tracking emissions, in their carbon reporting.
Frequently asked questions
How much idling is normal for a delivery van?
There is no universal benchmark, because it depends on climate, route type, refrigeration and time windows. Your own distribution is more useful: compare similar routes and vehicles and focus on the outliers.
Does idling damage modern diesel engines?
Prolonged low-load idling can contribute to issues such as soot build-up and incomplete regeneration of diesel particulate filters on some engines. The manufacturer's guidance for your vehicles is the reference.
Is restarting the engine worse than idling?
For modern vehicles, and especially those designed with stop-start systems, switching off during a stop of more than a short interval is generally recommended by fuel efficiency programmes. Follow the manufacturer's advice for specialised equipment.
Do electric vans have an idling problem?
Not in the fuel sense, but running heating or cooling while parked still consumes battery range. The same measurement discipline applies, measured in kilowatt-hours rather than litres.
