EV vs Petrol Cost Calculator UK 2026/27 — Total Cost of Ownership

The EV vs Petrol TCO Calculator→ compares the cost of owning an electric vehicle with a petrol or diesel car over the period you choose. It can include purchase price, energy or fuel, maintenance, insurance, vehicle tax, depreciation, finance assumptions and—when enabled—company-car Benefit in Kind (BIK).

The most important word is “compare”. The tool does not claim that every electric car is cheaper, or that every petrol car is cheaper. The result depends on the vehicles, annual mileage, ownership period, charging access, energy and fuel prices, finance, insurance, residual value and whether the car is privately owned or provided through work. A national average can be a useful starting point, but it is not your personal cost.

What total cost of ownership means

Total cost of ownership is broader than the amount paid at a forecourt or the monthly finance payment. A useful comparison asks what the car costs over the whole period and how much value remains at the end.

The calculator groups the main decision inputs into:

Some costs are reasonably easy to observe, such as the price you are quoted for insurance. Others are forecasts, particularly depreciation and future energy prices. The answer should therefore be read as a range or scenario, not as a guaranteed saving.

Start with the mileage you actually drive

Annual miles have a large effect on an energy comparison. A driver who covers a high mileage may see fuel and charging differences compound over several years. A low-mileage driver may find that purchase price, depreciation, insurance and finance dominate instead.

Use recent MOT records, workplace mileage, commuting days and regular journeys where possible. Do not include a planned road trip as though it repeats every week, and do not understate business or family mileage simply to make one car look better. If mileage is uncertain, run a low, central and high case.

The calculator uses annual miles and an ownership period to project energy or fuel use. It does not know your traffic, weather, driving style, payload, tyre pressure or motorway speed. Treat the vehicle’s advertised consumption as a starting point and adjust it when you have real data.

Home charging versus rapid charging

Charging cost is not one universal EV number. Home electricity, workplace charging, destination charging and rapid public charging can have very different prices. The calculator lets you test the share charged at home and the share charged rapidly so that the result reflects your access rather than assuming every mile is charged at the cheapest rate.

Before choosing an EV, ask practical questions:

• Can you park safely near a suitable domestic socket or chargepoint?
• Is the home electrical installation suitable, and will installation have a cost?
• How many miles are normally completed between overnight charges?
• How often would you need a public rapid charger?
• Does your workplace or destination offer reliable charging?
• Will the charging arrangement still work if you move house or change parking?

The GOV.UK electric vehicle chargepoint grant guidance may be relevant to some households and properties, but eligibility and grant details must be checked against the current official rules. Do not subtract a grant from the calculator unless you have confirmed that you qualify and know the actual installation price.

Home charging also has an opportunity cost: the electricity bill arrives at home rather than at a fuel station. If you charge through an employer, salary-sacrifice scheme or a business arrangement, check how the reimbursement and tax treatment works instead of assuming the private rate applies.

Petrol and diesel fuel assumptions

Fuel cost depends on the price you pay and the car’s real-world efficiency. Use a recent local price or a conservative scenario and test what happens if fuel becomes more expensive or less expensive. A fuel-price input is not an official forecast.

Avoid comparing an optimistic EV efficiency figure with a pessimistic petrol figure. Use the same driving pattern and ownership period for both cars. If one vehicle is larger, heavier or more powerful, acknowledge that the comparison may be about a different level of performance or space as well as a different powertrain.

The useful output is cost per mile plus total cost over the period. Cost per mile can highlight the operating difference, but it does not include the fixed costs that may decide the purchase. A car that is cheap to fuel can still be more expensive overall if its purchase price, depreciation, insurance or finance cost is materially higher.

Purchase price, finance and monthly affordability

The calculator can show a purchase or finance scenario, but the monthly payment is not the same as total cost. A low payment may result from a larger deposit, a longer term, a final balloon payment or a different vehicle price. Compare the deposit, interest, total amount payable, ownership at the end and the effect on your cash flow.

If you are comparing a cash purchase with a financed car, record the assumptions clearly. The opportunity cost of using savings is personal and may be relevant, but it should not be silently inserted as a guaranteed return. If the finance quote changes with credit score, term or mileage, use the actual quote rather than a generic rate.

Salary sacrifice is also a separate arrangement. A scheme can bundle insurance, servicing, tyres or other benefits, and the employee’s net cost depends on salary, pension, tax, National Insurance and employer policy. The standard TCO comparison is not a complete salary-sacrifice quotation. Compare the employer’s written offer with the private-purchase result on the same vehicle and period.

Depreciation and residual value

Depreciation is often the largest uncertain input. There is no single official depreciation rate for EVs, petrol cars or diesel cars. Residual value depends on model, age, mileage, condition, battery confidence, warranty, supply, demand, incentives and the state of the used-car market.

Use a vehicle-specific residual-value estimate where possible. Run a lower-residual-value EV scenario and a lower-residual-value petrol scenario rather than assuming one fuel type always holds value better. The calculator’s depreciation result is only as reliable as those assumptions.

A simple way to think about depreciation is:

purchase price − expected value at the end of the ownership period

That is not the same as the finance balance. You can still owe money after a vehicle’s market value changes, especially with a large final payment. If you plan to sell before the finance term ends, include the settlement figure and a realistic sale value.

Insurance, tyres and maintenance

Insurance should be based on the vehicle, driver, postcode, use, excess and quote date. EV insurance may differ from petrol insurance for reasons that have nothing to do with energy cost, including repair network, parts availability, vehicle value and battery-related work. Obtain comparable quotes rather than assuming a percentage uplift or saving.

Maintenance also needs a balanced treatment. An EV may have fewer engine and exhaust-system service items, but it still has tyres, brakes, suspension, fluids, software, air conditioning, inspections and repairs. Heavy vehicles and high torque can affect tyre wear. A petrol or diesel car has different service requirements and can have different repair risks as it ages.

Use the editable maintenance and insurance inputs for a real quote or a cautious estimate. Do not turn a general statement about fewer powertrain parts into a guaranteed annual saving.

Vehicle Excise Duty and tax inputs

Vehicle tax rules depend on the vehicle, first registration date, list price rules and the tax year. Check the current GOV.UK vehicle tax rate tables for the car you are considering. The calculator’s VED assumption should be treated as an input to check, not a substitute for the official vehicle-specific rate.

The tax position can also change when a vehicle is purchased by a business, provided as a benefit or used for business mileage. Private ownership, company ownership, salary sacrifice and a company car are different arrangements. Keep the ownership model consistent when reading the total.

Company-car BIK: use it only for the right question

If an employer provides the car and private use is allowed, company-car BIK can materially change the comparison. GOV.UK explains that company-car tax is calculated using the car’s appropriate percentage and the vehicle’s list-price-based value, with the employee’s tax rate affecting the personal charge. The HMRC appropriate-percentage table should be checked for the relevant emissions and tax year.

For 2026/27, the calculator presents a 4% appropriate-percentage scenario for a zero-emission car. That percentage does not by itself tell you the tax bill. You still need the car’s P11D value, the employee’s marginal tax rate, the availability period, any capital contribution and the employer’s actual benefit arrangement. A petrol or diesel car depends on its CO₂ figure and the applicable HMRC band.

Company-car tax is not the same as private total cost. An employee may not pay the purchase price or insurance directly, while the employer may provide servicing and cover. Compare the employee’s net benefit cost with the private alternative, including the salary or cash allowance given up. If you are comparing salary sacrifice, use the employer’s full quote.

The GOV.UK 2026/27 car and van benefit charges is a useful official reference for the relevant tax-year announcement. It does not replace checking the exact vehicle and benefit facts.

Five-year results are projections

The tool can compare a five-year period, but five years is an assumption, not a forecast of your actual ownership. If you normally change cars after three years, run three years. If you keep cars until repair costs rise, run a longer period and include that uncertainty.

Compare the result at several ownership periods:

If the result changes from EV to petrol depending on the period, the decision is about risk and flexibility as much as arithmetic. Consider whether you can sell or exit the arrangement without a large loss if your mileage or charging access changes.

How to stress-test the answer

Do not stop at the default preset. Change one assumption at a time and then run a combined downside case. Useful tests include:

1. Reduce annual miles.
2. Increase the rapid-charging share.
3. Increase or reduce electricity and fuel prices.
4. Use a lower residual value for both vehicles.
5. Add a realistic insurance difference from actual quotes.
6. Extend or shorten the ownership period.
7. Turn company-car mode on only if you genuinely receive a company car.
8. Compare cash purchase, finance and the employer’s actual salary-sacrifice offer separately.

The result is more persuasive when the preferred option remains reasonable across several scenarios. If a small change reverses the winner, report the result as uncertain and focus on which input is worth verifying first.

Questions to ask before buying

Check the written vehicle price, finance terms, insurance, warranty, servicing schedule, tyre costs, charging installation, public-charging access and expected resale value. For a company car, confirm P11D value, emissions, appropriate percentage, private-use rules, employee contributions and the employer’s tax treatment.

Also consider non-financial fit: boot space, towing, long-distance charging time, accessibility, local air-quality restrictions, parking and whether the car is available when needed. A lower modelled cost is not a saving if the vehicle does not meet the journeys you actually make.

Frequently Asked Questions

Bottom line

The EV vs petrol cost calculator is a decision aid, not a universal verdict. Use it to compare the complete ownership picture: acquisition, finance, energy or fuel, charging access, insurance, maintenance, vehicle tax, depreciation and the correct company-car scenario where relevant.

Start with your actual mileage and charging routine, run low and high cases, and replace generic assumptions with quotes or vehicle-specific evidence. For company cars, verify the P11D value and current HMRC appropriate-percentage rules. For private cars, check the current vehicle tax position and the real cost of financing and insurance before committing.

Official sources

• GOV.UK: Tax on company cars — company-car benefit calculation context.
• GOV.UK: Company car appropriate percentages — emissions and appropriate-percentage rules.
• GOV.UK: 2026 to 2027 car and van benefit charges — current tax-year benefit-charge publication.
• GOV.UK: Vehicle tax rates — current vehicle-tax rate tables.
• GOV.UK: Electric vehicle chargepoint grant — current eligibility and grant guidance.
• GOV.UK: Get ready to drive your vehicle — vehicle-tax and driving checks.

This is general educational information for the UK 2026/27 tax year. It is not vehicle, tax, finance or employment advice, and it does not guarantee a saving. Check current official guidance, vehicle-specific quotes and the terms of any employer scheme before acting.