Last reviewed: September 2025
EV Decision Compass provides fleet managers and finance leaders with an independent, data-driven view of the Total Cost of Ownership (TCO) for electric and diesel fleets. Our methodology combines the latest UK market data, government policy, and real-world fleet case studies to ensure results are transparent, robust, and relevant.
1. Data Sources
We draw on a combination of trusted, publicly available sources and proprietary fleet benchmarks:
- Energy prices
- Domestic charging: Ofgem quarterly price cap (updated September 2025).
- Public charging: Zapmap Price Index (updated monthly).
- Fuel prices: RAC Foundation / AA Fuel Reports.
- Vehicle data: SMMT registrations, Cap HPI cost benchmarks, manufacturer lists.
- Fiscal data: HMRC (Advisory Electric Rate split: 8p/14p as of September 2025), DVLA (VED changes from April 2025).
- Maintenance and insurance: Cap HPI and major fleet insurers’ published averages.
- Residual values: Glass’s Guide and fleet leasing partners.
2. Key Assumptions
- Mileage: Scenarios modelled at 10k, 20k and 30k miles per year.
- Ownership horizon: 4 years (aligned with typical UK fleet replacement cycles).
- Charging mix: Standard case assumes 70% home/depot charging and 30% public charging, with sensitivity testing on both ends.
- VAT treatment: 5% for domestic charging, 20% for public charging.
- Insurance & maintenance: Based on 2025 averages; EVs currently show 15–20% lower scheduled maintenance costs.
3. Policy Context
Our model reflects the latest regulatory landscape:
- VED for EVs: From April 2025, battery electric vehicles pay standard VED (~£195/year).
- Expensive Car Supplement: Applies to EVs above £40k list price; inflation means more EV models are now included.
- ZEV Mandate: While not a direct fleet tax, it influences supply and pricing; scenarios include a sensitivity for restricted EV availability.
- HMRC AER split: 8p (home/depot) and 14p (public) from September 2025.
4. Real-World Validation
Model results are cross-checked against fleet case studies in logistics, services, and corporate fleets. This ensures that outputs reflect real-world operating conditions, not just theoretical averages.
5. Updates & Transparency
- Quarterly reviews: Energy, fuel, and policy inputs are reviewed at least every three months.
- Version history: All changes to assumptions and data sources are logged below.