Your PHEV fleet is probably running on petrol
4 min read · 31 March 2026. A fleet manager at a healthcare company asked us to investigate one of their vehicles. The driver had raised a complaint — the Ford Kuga wasn't performing anywhere near its claimed fuel efficiency. They suspected a fault.
There was no fault.
The vehicle was working exactly as designed. The driver simply wasn't plugging it in.
What the data showed
The vehicle in question was a Ford Kuga ST Line X PHEV — a plug-in hybrid with a published WLTP fuel economy figure of 313.9mpg and a CO₂ rating of 21g/km. On paper, one of the most efficient vehicles in its class.
Orbis pulled the real data directly from the vehicle via the manufacturer API. Here's what it found:
The published figure of 313.9mpg assumes the vehicle is charged regularly and driven on electric power for short journeys. When that doesn't happen — when the battery is never topped up and the vehicle runs entirely on petrol — the efficiency collapses. The 41.6-mile electric-only range sits unused. The petrol engine carries the full load.
Why this happens so often
This isn't unusual. It's arguably the defining problem of the current PHEV fleet generation.
PHEVs were sold to fleet operators on the strength of their published efficiency figures — figures that only hold up when drivers charge them consistently. But the conditions that produce those figures almost never exist in practice.
Drivers on fuel benefit have no financial incentive to charge. If the employer pays for fuel, the driver has no reason to manage consumption. The cost of not plugging in falls entirely on the company budget, not the driver's pocket.
The driver had zero incentive to charge. The employer was absorbing £1,207 in unnecessary fuel costs annually — on a single vehicle. Multiply that across a mixed fleet of 20 PHEVs and you're looking at over £24,000 a year in waste that doesn't show up anywhere until someone looks.
There's also the infrastructure problem. Drivers without home chargers, or without reliable workplace charging, simply can't maintain the plug-in frequency the WLTP figure assumes. Information about home charger availability and fuel benefit status is exactly what lets a fleet manager act — whether that's installing home charging, adjusting fuel benefit policy, or replacing the vehicle at next renewal with a more appropriate choice.
The ESG problem hiding in plain sight
The compliance exposure goes beyond fuel costs. A vehicle emitting 6.8 times its declared CO₂ figure is a significant problem for any fleet with Streamlined Energy and Carbon Reporting (SECR) obligations.
SECR requires companies to report actual emissions, not manufacturer claims. If your fleet carbon report is built on WLTP figures for vehicles that aren't being charged, your report is wrong. Not slightly wrong — substantially wrong. And when an auditor or sustainability team starts asking questions about methodology, "we used the published figures" is not a defensible answer.
Orbis calculates actual Scope 1 emissions from real consumption data pulled directly from the vehicle. It doesn't estimate. It doesn't use HMRC mileage rates. It uses the fuel the vehicle actually burned.
What Orbis showed the fleet manager
When we ran the OPCI™ audit for the healthcare fleet, the fleet manager could see immediately — not from a complaint, not from a spreadsheet reconciliation, but from live vehicle data — that they had a charging behaviour problem, not a vehicle fault.
The actionable output was clear: this vehicle needed a conversation with the driver about charging, a review of whether home charging infrastructure was available, and a policy decision about fuel benefit. Three concrete actions that couldn't have been identified without the data.
That's what Orbis IO is for. Not dashboards for their own sake. Answers that a fleet manager can act on before 9am.
What to check on your PHEV fleet
If you run PHEVs and you haven't looked at actual plug-in frequency, this data is almost certainly not an outlier. Ask yourself:
Are you reporting WLTP figures for ESG? If so, and if your PHEVs aren't being charged, your CO₂ reporting is materially understated.
Are drivers on fuel benefit? If yes, there is no financial mechanism pushing them to charge. You're absorbing the cost difference.
Do you know actual MPG per vehicle? Not from the dashboard trip computer — from the vehicle's own data. If not, you're managing by assumption.
When did you last review BIK implications? PHEVs attract low BIK rates on the assumption they're being charged. HMRC has increasing visibility into whether that assumption is true.
See the full OPCI™ methodology and a live Volkswagen Tiguan example in our OES™ and OPCI™ breakdown — or book a twenty-minute walkthrough and we'll run the audit on your own PHEVs.
Book a 20-minute walkthrough →