THRIVE Fleet Cost Index

The Index turns two official numbers - the weekly average diesel pump price and HMRC's advisory electric rate - into the figure a fleet manager actually needs: how much more a diesel van costs to fuel, per mile, than an electric one. A ratio above 1 means diesel is dearer; the higher it climbs, the stronger the running-cost case for electrifying.

Because it is rebuilt every Tuesday from source data, it moves with the pump - not with anyone's marketing. Pair it with the break-even mileage to see how quickly that per-mile saving repays an electric van's price premium.

• Diesel van: the DESNZ weekly average UK diesel pump price (pence/litre) × 4.54609 litres/gallon ÷ 36 mpg, our documented representative diesel-LCV combined economy.
• Electric van: HMRC's advisory electric rates, used as a proxy: 7p/mile home, 15p/mile public (separate rates since 1 September 2025). HMRC sets these for reimbursing business mileage in company cars, from car energy use; they are not an official electric-van rate, and a van uses more electricity per mile than a car, so treat the electric figure as a floor. For van costs at real electricity prices, see fleet charging costs.
• Index: diesel pence-per-mile ÷ a blended EV pence-per-mile assuming 70% of charging at the home rate and 30% at the public rate (THRIVE's assumption). Both sides include VAT. Nothing else is counted: no purchase price, maintenance, insurance or charging equipment.

Sources: DESNZ weekly road fuel prices and HMRC advisory fuel rates, used under the Open Government Licence v3.0. All constants read live from our rates API, never hardcoded.

Figures checked against GOV.UK on 27 October 2026.

Free JSON API - no key, open CORS, cache-friendly:

• /api/v1/cost-index - JSON
• /api/v1/cost-index?format=csv - CSV

curl https://www.thrivefleet.co.uk/api/v1/cost-index

{ "unit": "pence per mile",
  "weeks": [ { "week": "…", "diesel_van_ppm": …, "index_value": … } ] }

Free to use. Please credit THRIVE and link to the page a figure came from: a request, never a condition of use. See the data terms and the API guide.