Cost per kilometer of a mixed fleet: the method that avoids calculator pitfalls (2026)
The same kilometer, three different prices depending on who calculates
A fleet manager asks three different tools for the cost per kilometer of the same regional route. The online calculator from a carmaker gives one figure. A full accounting analysis of total cost of ownership (TCO) gives another. The telematics dashboard of his own vehicles displays a third. The three don't contradict each other by mistake: they don't measure the same thing.
The calculator applies a simple formula, consumption multiplied by a default energy price. TCO analysis adds maintenance, insurance, financing and taxation. The dashboard measures what actually happened, route by route. None of the three is wrong in itself — but confusing their results leads to poorly calibrated purchasing or allocation decisions.
This text details the basic formula, shows where it breaks down the moment a plug-in hybrid enters the picture, then aligns all three approaches on a common kilometer basis, each answering a different question.
Key takeaways
- Comparing liters per 100 km and kWh per 100 km directly makes no sense: both must be converted to cost per kilometer, or cost per delivery, before any comparison.
- At equivalent specification and performance, an electric vehicle can cost between 5% and 30% more to buy than a combustion engine vehicle depending on segment, according to BDO firm's study (2022) on the Belgian market — a gap that commercial calculators pass over in silence.
- The cost per kWh for a fleet electric vehicle varies by charging location (depot, public charging station, home), timing (day or night) and mode (slow AC charging or fast DC charging): there is no single electricity price for a fleet.
- Electrification of professional fleets is progressing gradually; electric commercial vehicles remain in the minority against combustion engines, which keeps mixed fleets going for several more years.
The basic formula (and why the hybrid already complicates it)
The most widespread calculation for a combustion or electric vehicle fits in one line: consumption per 100 km multiplied by energy price, or liters × price per liter for combustion, or kilowatt-hours × price per kWh for electric. This is the logic retained by BYD's online calculator (drive.bydauto.be), and it has the merit of simplicity.
The problem starts with the plug-in hybrid. The same BYD calculator offers multiple calculation modes for a single vehicle: a weighted mode that blends electric and combustion routes according to a usage assumption, a "hybrid" mode that assumes continuous mixed usage, and an "empty battery" mode that counts only the combustion portion. Each applies the same basic formula — (price per liter × liters/100 km) + (price per kWh × kWh/100 km) — but with different weightings, producing three distinct results for the same vehicle.
This multiplicity is not a minor technical detail: it means a cost/km displayed for a plug-in hybrid depends as much on the calculation mode assumption chosen as on energy prices themselves. Before even comparing multiple vehicles, you must therefore know which calculation mode produced the figure in front of you.
The trap of carmaker calculators: default values, not real prices
The BYD calculator illustrates a second, more subtle trap: the default prices used. The tool displays for example €0.31/kWh and 19.9 kWh/100 km for electric, €2.300/L and a combination 0.4 L + 17.9 kWh for hybrid, and €2.500/L for diesel — values presented as illustrative, without date or market source attached.
The same tool claims, without figures, that an electric vehicle costs less to maintain, invoking fewer moving parts and a two-year maintenance interval. The argument is plausible but remains a commercial assertion, not verifiable data.
Faced with these undated shortcomings, the BDO firm's study (2022, "Electrification of the fleet" report, covering the Belgian market) retains explicitly referenced prices including VAT: €1.636/L for gasoline and €0.4235/kWh for electricity, to which is added €500 per year in charging station cost per electric vehicle. This same report concludes that at equivalent specification and performance, purchasing an electric vehicle costs between 5% and 30% more than a comparable combustion vehicle, a gap varying by vehicle segment and assumptions — a finding that directly contradicts the "less expensive without compromise" electric suggestion put forward by commercial calculators.
The practical lesson is simple: an undated default price serves to illustrate how a tool works, not to budget a fleet. Energy rates and purchase prices must come from the fleet manager's actual contracts, not from a calculator page.
True cost per kilometer goes beyond energy alone
A cost/km useful for decision-making aggregates several items that the consumption × price formula ignores. The BDO report (2022) details this composition: maintenance, tires, insurance and roadside assistance, fuel consumption measured according to the WLTP cycle, charging station cost, and a portion of non-recoverable VAT that weighs differently depending on vehicle type. The precise rules of tax deductibility and VAT applicable to company vehicles change regularly in Belgium — notably the phased elimination of tax deductibility for new combustion vehicles implemented in recent years — and should be verified with the SPF Finance or an approved accountant rather than deduced from a general-interest article.
The financing effect, often overlooked
Financing changes the ranking by itself. According to BDO (2022), the monthly rental of a vehicle in the "higher middle class" category goes from approximately €560/month before tax in gasoline to €445/month before tax in electric; the study does not allow precise isolation of the portion attributable to residual value, interest rates or leasing policies in this gap. A calculation limited to energy never sees this gap, yet it directly affects total monthly cost.
The annual TCO figures published in the same report illustrate the scale of these combined effects, on a 2022 basis: for a "lower middle" category vehicle, TCO reached approximately €7,300/year in gasoline versus €8,000/year in electric, a €700 surcharge. For a "higher middle" vehicle, conversely, gasoline TCO reached approximately €11,000/year versus approximately €8,600/year in electric, a gap of around €2,400/year. These figures date from 2022 and must be updated with energy tariffs and financing conditions in force at the time of calculation — they serve here as a verifiable basis to understand the mechanics, not as current tariff reference.
Step-by-step method: calculating comparable cost/km
The following example is hypothetical: it serves to show calculation mechanics, not to provide a figure to copy. Every price must be replaced with the reader's actual tariff, never a calculator default value.
Take three fictional vehicles in the same segment, with hypothetical annual mileage of 20,000 km (1,667 km/month) and energy prices including VAT as retained by BDO (2022) as a starting basis, to be updated with your own contracts:
- Gasoline: hypothetical consumption of 6 L/100 km × €1.636/L = €9.82/100 km, or approximately €0.098/km for energy alone.
- Plug-in hybrid: weighted mode assumption of 2 L/100 km + 10 kWh/100 km → (2 × 1.636) + (10 × 0.4235) = €7.51/100 km, or approximately €0.075/km for energy.
- Electric: hypothetical consumption of 17 kWh/100 km × €0.4235/kWh = €7.20/100 km, to which is added the charging station cost of €500/year spread over 20,000 km, or €0.025/km — total energy and charging of approximately €0.097/km.
You must then add the financing effect. Using the monthly before-tax rentals observed by BDO for a comparable segment — €560/month in gasoline versus €445/month in electric — and the 1,667 km/month mileage adopted above, financing represents approximately €0.336/km for gasoline versus €0.267/km for electric. Published data do not provide an equivalent for the hybrid; this item must be requested directly from the leaser.
Adding energy and financing, gasoline reaches approximately €0.434/km versus €0.364/km for electric in this specific example — a gap that would reverse with different mileage or energy price assumptions. This is precisely why method matters more than the numerical result: change annual mileage or electricity rate, and the ranking can flip.
Mixed fleet: why the same method must apply route by route
An average cost/km calculated for an entire fleet masks very different realities depending on the routes. The Optivo blog, in its article on managing the diesel-to-electric transition in mixed fleets (2026), identifies three frequent errors: separate data collection systems between combustion and electric vehicles, fragmenting information; vehicle allocation to routes by habit rather than based on actual route data; and the absence of measurement allowing objective cost per km comparison on the ground.
The article recommends simple allocation rules: urban routes with numerous stops are suited to electric, long interurban routes are still better covered by diesel or hybrid, and tight delivery windows require guaranteed range rather than theoretical range.
Maintenance that doesn't compare item by item
Maintenance well illustrates why cost/km must be broken down by powerplant type. Diesel involves oil changes, filters and belts at regular intervals. An electric vehicle requires different monitoring: battery health status, cooling circuit, and brakes that typically wear more slowly thanks to regenerative braking. Ignoring this difference amounts to applying the same maintenance allowance to two vehicles that don't wear the same way.
As Maurizio Piredda, financial director and co-founder of Optivo, sums it up: "The mixed fleet isn't a temporary transition phase. It's the new normal for years to come." As long as this coexistence continues, cost/km only makes sense relative to specific usage, not as an overall fleet average.
Three methods, three different figures: which one to believe?
The three approaches described above are not competing; they answer different questions.
| Method | What it measures | Data needed | Main limitation |
|---|---|---|---|
| Carmaker calculator | An order of magnitude for energy alone | Announced consumption, default price | Undated prices, maintenance not quantified |
| Accounting TCO model | Complete cost including financing and taxation | Purchase price, rental, maintenance, contractual energy price | Dated figures, requiring regular updating |
| Telematics dashboard | Real observed cost by route | Trip, charging and vehicle consumption data | Requires sufficient history to be reliable |
The carmaker calculator provides quick first intuition, without commitment. The accounting TCO model serves to compare purchase or lease scenarios before decision. The telematics dashboard verifies, after the fact, what actually happened on the ground, route by route. None of the three methods alone suffices to budget a mixed fleet; they complement each other in this order, from estimation to verification.
Verification checklist before comparing two cost/km figures
Before accepting a cost/km displayed by any tool, five questions allow evaluating its reliability:
- Is the energy price used an actual contractual tariff, or an undated default value?
- Is maintenance differentiated by powerplant — oil changes and belts for combustion, battery monitoring and regenerative braking for electric — or treated with a single allowance?
- Are financing and residual value included, knowing they can reverse a ranking based on energy alone?
- Is tax treatment mentioned without verification against an official source — in which case it must be flagged as to be confirmed, not figured as settled?
- Is cost/km related to actual usage (route type, annual mileage) rather than an overall fleet average?
A figure that doesn't answer these five points remains a partial estimate, useful for first intuition but not for arbitrating a purchase.
Frequently asked questions
Is the electricity price for a fleet unique? No, and that's the practical consequence that matters: a manager cannot apply a single average rate to his entire electric fleet. He must cross actual charging data returned by the telematics dashboard — by site, by time of day and by charging mode — with energy contracts specific to each charging point, otherwise the displayed cost/km remains an approximation.
Is a plug-in hybrid always cheaper per kilometer than diesel? That depends entirely on the calculation mode adopted — weighted, continuous hybrid or empty battery — and the driver's actual charging profile. A rarely recharged hybrid behaves economically like a heavier combustion vehicle, not like a low-energy cost vehicle.
Should I trust a carmaker's calculator? It works for quick initial estimation, but its default prices don't replace a contractual rate or a calculation including differentiated financing and maintenance.
How often should a mixed fleet's cost/km be recalculated? Whenever a structuring factor changes — energy contract renewal, leaser change, or significant evolution of routes assigned to each powerplant — rather than at fixed intervals, because a frozen cost/km quickly loses relevance.
What a unified method changes
As long as the share of electric vehicles in fleets remains minority, having a coherent comparison method — rather than an isolated figure from a calculator — becomes a management asset in its own right, not just a one-off accounting exercise. The question is no longer merely "how much does this vehicle cost per kilometer," but "on what basis was this figure obtained, and does it still apply to this specific route." This verification discipline, more than any figure fixed in time, distinguishes a well-managed mixed fleet from one navigating by dead reckoning.
--- This article is published for informational purposes only and does not replace a calculation performed with your fleet's actual contractual rates. Have your cost/km assumptions validated by your accountant or fleet manager before any purchase or lease decision.
