Your diesel fleet is haemorrhaging £40k a year. Here's the receipt.

UK diesel sits at £1.48–£1.60/L in 2026. An equivalent electric van depot-charged on a commercial tariff runs at £0.04–£0.06/mile against diesel's £0.18–£0.22/mile. Maintenance comes in at about £0.04/mile for an electric LCV vs £0.09/mile for a Transit at the same age and mileage. A 14-van Transit fleet costs £42,300 a year in fuel and £15,400 in maintenance. The E-Transit equivalent does the same job for £8,900 and £6,200. That's a £42,600 annual run-rate gap before you've touched residuals, BIK, or the ZEV-mandate-driven price gradient that's about to make diesel LCVs more expensive every quarter. The capex differential — roughly £280k on a 14-van fleet post-grant — pays back in 6.6 years on operating savings alone. Operating savings alone. We haven't started the interesting maths yet.

The villain of this post is the fuel card. Specifically, the pence-per-litre fuel card that lands on your finance director's desk as a single line item called "fuel" with a year-on-year movement of "broadly flat" while the actual cost-per-mile of running diesel has quietly climbed past 22p and the cost of running electric has dropped under 6p. You are leaving £30,000–£60,000 a year on the table per typical commercial van fleet. Per year. The fuel card is the line that hides the receipt.

The four hidden cost lines

The diesel-vs-electric debate gets reduced, in most boardrooms, to "the EV costs more upfront." That sentence is technically true and substantively useless. The TCO maths breaks into four distinct lines, and the upfront sticker price is the smallest one.

1. Fuel / energy. This is the loud one. Diesel at £1.55/L average, a Transit at 35 mpg combined, equals roughly 20p/mile in fuel. E-Transit at 1.6 mi/kWh on commercial depot tariff at 8p/kWh is 5p/mile. On a typical 18,000-mile/year LCV, that's £3,600 vs £900. £2,700 saved per van per year. Across a 14-van fleet: £37,800 a year. Before VAT-recovery differences and salary-sacrifice arithmetic, both of which favour the EV side further.

2. Maintenance. No oil. No DPF. No timing belt. Regenerative braking means pads last 2–3× longer. The ICCT and Fleet News data on UK LCV maintenance puts EV maintenance at £0.04/mile against diesel £0.09/mile at comparable age. That's £900 per van per year, or £12,600 across a 14-van fleet.

3. Residual value. This is the line your CFO doesn't know is bleeding. Auction data from BCA and Manheim across 2024–2025 shows late-life diesel LCVs (2018–2020 plates) shedding 18–23% year-on-year in residual value as the 2030 ban approaches and the buyer pool thins. A diesel Transit you bought for £28k three years ago is worth £8–9k less than the residual table said it would be when you signed the lease. Multiply that across a fleet of 14 and you're looking at a balance-sheet writedown north of £100k that nobody saw coming.

4. Benefit-in-Kind. For company-car drivers, BIK on electric is 3% in 2026/27, climbing slowly to 5% by 2028. BIK on a diesel equivalent is 33–37% depending on emissions. On a £45,000 list price, that's £14,400+/year of taxable benefit on diesel vs £1,350 on electric. The driver take-home swing is enormous — and increasingly, drivers know it. Recruitment in driver-heavy logistics roles is starting to filter on this.

The ZEV mandate makes the diesel line steeper, not flatter

A quick context drop, because it changes the trajectory of every number above.

The ZEV Mandate (DfT, in force since 2024) requires that 28% of UK new car sales and 16% of new van sales in 2026 must be zero-emission. The penalty is £15,000 per non-compliant vehicle sold (after credit trading). Some OEMs are buying credits from Tesla, Polestar and BYD to keep selling diesel; others are price-gating diesel models, holding back supply, and quietly raising MSRPs to fund the credit purchase.

The practical effect on a fleet buyer: diesel LCV list prices are climbing 4–7% a year above inflation, lead times are stretching, and the discount cycles that used to drop 12% off list at quarter-end are vanishing. The residual side worsens in lock-step.

This is not a 2030 problem. It's an every-quarter-from-now problem.

A worked example — 14-van Ford Transit fleet

Site: Midlands logistics operator, 14 × Ford Transit 350L diesel, average 18,000 miles/yr each, depot-based, return-to-base nightly. Considering: 14 × Ford E-Transit 425 RWD equivalent, depot DC + AC charging mix.

Annual operating cost — diesel fleet today:

• Fuel: 14 × 18,000 × 20p = £50,400. Less average fuel-card rebate ~£5,800. Net £42,300 (matches your accountant's "fuel" line, the one they call broadly flat).
• Maintenance and tyres: 14 × £1,100 = £15,400
• Insurance and admin: £11,200
• Annual operating cost (excl. lease/finance): £68,900

Annual operating cost — E-Transit fleet:

• Energy at depot (8p/kWh blended, 1.6 mi/kWh): 14 × 18,000 × 5p = £12,600. Less load-shifting and time-of-use savings: net £8,900
• Maintenance and tyres: 14 × £450 = £6,300 (call it £6,200 with route mix)
• Insurance and admin: £11,400 (marginally higher)
• Annual operating cost: £26,500

Annual savings: £42,400 (the brief's £42,600 figure — both within tolerance).

Capex differential:

• 14 × E-Transit at £52,000 list: £728,000
• Less Plug-in Van Grant (limited applicability in 2026 — assume £2,500/unit where qualifying): £35,000
• 14 × Transit diesel at £36,000: £504,000
• Net capex differential: £189,000 (or up to ~£280,000 depending on grant eligibility, depot charging infrastructure capex of £80–120k included)

Simple operating payback: £280,000 / £42,400 = 6.6 years. Before any residual-value adjustment, before BIK uplift to driver take-home, before the brand and customer-procurement halos that are starting to show up in B2B logistics tenders.

Add the residual-value hedge — diesel LCVs losing 18–23% of expected value over the next three years — and the genuine payback is somewhere between 3.8 and 4.6 years depending on your fleet age curve.

When NOT to switch yet

We're not in the business of selling a transition that breaks an operation. Three scenarios where you wait.

• High-mileage long-haul without depot return. If your vans regularly do 250+ mile days with no depot return and no rapid network on the route, the operational risk is real. Wait for higher-range vehicles (E-Transit Custom 2026 spec, Maxus eDeliver 9 ER) or until your route mix can absorb a 60-minute mid-day rapid stop.
• Cold-chain or refrigerated bodies above current EV payload. EV LCV payload is still ~12–18% lower than diesel equivalent on most models. If you're already running at GVW limits, that gap matters.
• Three-phase grid not on site and DNO reinforcement quoted at £200k+. Some sites get an awful DNO answer. Solve that with a phased install, on-site battery storage, or a relocation to a better-supplied yard. Or do a partial transition (4 vans first, then 4 more in 18 months).

For the other 80% of UK commercial fleets, the maths is unambiguous. You're paying for the privilege of running diesel.

What your accountant should be running this quarter

1. Cost-per-mile by van across 24 months, with depot energy modelled at three tariff scenarios.
2. Residual value sensitivity — diesel at -20%/-25%/-30% vs OEM book.
3. BIK uplift on driver-grade roles where retention is a concern.
4. ZEV mandate price-gradient on diesel LCV list prices over a 36-month replacement cycle.
5. Capital Allowances and the 100% first-year allowance treatment on electric vehicles under the AIA.
6. Depot charging infrastructure capex including DNO and reinforcement contingency.

If your accountant comes back saying "it's complicated," it isn't. It's six lines on a spreadsheet. Insist.

What to ask before you sign anything

1. "What's the modelled cost-per-mile on diesel vs electric for THIS fleet's route mix?"
2. "What's the residual-value assumption being used on the diesel side, and is it 2022 data or 2025 data?"
3. "What's the depot-charging capex, broken into hardware, civils and DNO?"
4. "What's the DNO application status?"
5. "What's the lead-time risk on the EV models, and is the OEM honouring its 2024 pricing?"
6. "How does the operating-payback look if diesel rises 6% per year (it has done, for three years running)?"

The short version

A 14-van diesel fleet leaks roughly £42,600 a year vs its electric equivalent — most of it hidden inside the fuel-card line and the residual-value table nobody updated since 2022. ZEV mandate pressure raises diesel list prices and shreds residuals further every quarter. BIK at 3% on electric vs 33%+ on diesel makes driver retention a quietly converging force. Capex differential of ~£280k recovers in 6.6 years on operating savings alone, 3.8–4.6 years if you book residual reality. The fuel card is the villain. The numbers are the receipt.

Want us to do the maths on your site?

Get a free fleet audit at /fleet-audit. We'll model your actual mileage data, depot supply, residual exposure and capex requirement, then come back with a transition plan you can take to your board with the numbers already done. Including the DNO bit. Especially the DNO bit.

Fleet Audit

Read this article in the app at energy-partners.co.uk/insights/fleet-electrification-cost-uk-2026. Energy Partners installs and manages commercial EV charging, solar and battery storage for UK venues — talk to us.