Methodology and sources
Every calculator on this site starts from a default value. This page lists all of them, says where each one comes from, and says plainly which are sourced figures and which are assumptions. Nothing here is a claim about your vehicle or your electricity plan — the point of the calculators is that you replace these numbers with your own.
How to read this page
Each figure below is marked one of two ways.
- Sourced — the value is taken from a named external source, and that source is given.
- Assumption — the value is a reasonable working figure chosen to make the calculator useful out of the box. It is not measured, not surveyed, and not taken from a published dataset. Treat it as a starting point, not as evidence.
At the time of this review, the majority of the defaults on this site are assumptions. UK electricity and fuel prices vary so widely by retailer, tariff, time of day, state and site that a single national figure would be misleading whichever number was chosen. Rather than attach a citation that does not really support the number, the figures are labelled honestly and every one of them is editable in the calculator.
All defaults live in one file, assets/js/pricing-data.js. The values below are read from that file. If a figure on a calculator disagrees with this page, the file is the source of truth and this page is out of date — please say so.
Electricity price tiers
Six price tiers appear in the rate comparison on every cost calculator. They are round numbers chosen to span the realistic UK range from cheap overnight EV tariffs to the most expensive public ultra rapid charging.
| Tier | Default price | Basis |
|---|---|---|
| Home solar | £0.06 per kWh | Assumption. Not a tariff you pay — it is the solar feed-in credit given up by self-consuming rather than exporting. UK Smart Export Guarantee rates averaged roughly 3–6 c/kWh through 2026 and have been falling as daytime solar exports grow. |
| EV off peak | £0.07 per kWh | Assumption. Reflects dedicated overnight EV tariffs offered by some UK retailers. Not all plans offer a rate this low. |
| Home off peak | £0.15 per kWh | Assumption. A typical off peak shoulder rate on a time-of-use plan. |
| Home standard rate | £0.26 per kWh | Assumption. A round figure for a flat residential tariff. Actual rates differ substantially between states and retailers. |
| Public AC | £0.49 per kWh | Assumption. Midpoint of the £0.40–£0.55 range this site quotes for public AC charging. |
| DC fast | £0.75 per kWh | Assumption. Within the £0.50–£0.75 range quoted for 50–150 kW public DC. |
| Ultra rapid DC | £0.85 per kWh | Assumption. Top of the range quoted for 250 kW+ public charging. |
How the solar figure is derived
Charging from your own rooftop solar does not produce an electricity bill, so it has no tariff to quote. What it does have is an opportunity cost: every kilowatt-hour you put into the car is one you did not export for a feed-in credit. That forgone credit is the honest price of solar charging, and it is what the £0.05 figure represents.
UK Smart Export Guarantee rates sat at roughly 3 to 6 pence per kilowatt-hour through 2026 and have been declining, because so much solar reaches the grid at midday that wholesale prices there are often near zero or negative. If your retailer pays more or less than 5 pence, enter your own feed-in rate as the solar price and every figure on the site will use it.
Two caveats worth stating plainly. This assumes the energy genuinely comes from your own generation, which means the car has to be plugged in during daylight — solar charging suits people who are home during the day or who have a charger at work, and does nothing for someone who only plugs in at night. It also ignores the cost of the solar system itself, on the reasoning that most people install solar for the household rather than for the car. If you are weighing up whether to install solar specifically to charge an EV, that is a payback calculation this site does not attempt.
These tiers are the site's own price ladder, not a published tariff schedule. They are used consistently everywhere so that comparisons between calculators are internally consistent. Enter your own rate to get a figure that means something for your plan.
Regional electricity rates
Ofgem sets the energy price cap by electricity distribution region rather than nationally, so the standard unit rate genuinely differs by where you live. Selecting a region in the My EV panel loads that region’s rate.
Figures are direct debit unit rates under the Ofgem cap for October to December 2026, around a published national average of 26.32p per kWh. Regional values are indicative. Two caveats matter more here than the regional variation itself: the cap is reset every quarter, so these move four times a year, and anyone on a fixed tariff is not on the cap at all. If you are on an EV tariff your overnight rate may be a quarter of the figures here. Enter your own rate — it will beat any regional average.
Public charging price ranges
Where a guide quotes a range rather than a single price, these are the ranges used.
| Charger type | Range used | Basis |
|---|---|---|
| Public AC charger | £0.44 – £0.59 per kWh | Assumption |
| DC fast charger (50 kW) | £0.59 – £0.79 per kWh | Assumption |
| DC rapid charger (150 kW) | £0.69 – £0.85 per kWh | Assumption |
| Ultra rapid charger (250 kW+) | £0.75 – £0.92 per kWh | Assumption |
Vehicle defaults
| Figure | Default | Basis |
|---|---|---|
| Battery size | 100 kWh | Assumption. A round number, deliberately at the larger end so costs are not understated. Replaced by your vehicle's real capacity when you set a vehicle with My EV. |
| EV efficiency | 26 kWh per 100 miles | Assumption. A mid-range figure for a medium EV. Replaced by the vehicle's rated figure when you set a vehicle. |
| Everyday charge window | 10% to 80% | Assumption, reflecting common charging practice and the range over which DC charging is fastest. |
| Petrol vehicle fuel use | 8.0 L per 100 miles | Assumption. A medium petrol car. Change it to match the car you are actually comparing against. |
| Annual distance | 7,500 miles | Assumption. A round figure for an average private vehicle. The ABS Survey of Motor Vehicle Use is the obvious source for a real figure; this site does not currently cite it, so the number is not presented as sourced. |
| Petrol price | £1.62 per litre | National average (RAC Fuel Watch, August 2026). Fuel prices move weekly and vary by city, so this one dates faster than any other default on the site. |
Vehicle specifications listed on the EV battery size list — battery capacity, WLTP range, maximum DC charging power — are taken from manufacturer specifications for the UK market. WLTP range figures are laboratory test results and are consistently optimistic relative to real driving.
Charger types and power
Charging time calculations use these nominal power figures. Real charging power is rarely constant: it depends on the vehicle's own limit, the battery's state of charge and temperature, and whether the charger is shared with another car.
| Charger type | Power used | Typically found |
|---|---|---|
| Portable charger | 2.3 kW | Standard power outlet |
| AC wall charger | 7 kW | Home wall box (single phase) |
| 3-phase AC charger | 22 kW | Home, workplace or destination charger |
| DC fast charger | 50 kW | Public fast charging station |
| DC rapid charger | 150 kW | Public rapid charging station |
| Ultra rapid charger | 250 kW | Public ultra rapid station |
What the time calculations exclude
Charging time is calculated as energy divided by power, at constant power. Real DC charging follows a curve that tapers as the battery fills, so real charging sessions take longer than this site estimates, particularly above 80%. The site does not model the charging curve, battery temperature, preconditioning, or the vehicle's own maximum DC intake beyond the value stored for a selected vehicle.
Ownership costs
| Figure | Value used | Basis |
|---|---|---|
| EV servicing, per year | £400 (midpoint of £300 – £500) | Assumption. No source. Actual servicing cost varies by manufacturer, service interval and whether the vehicle is under a capped-price plan. |
| Petrol servicing, per year | £500 – £800 | Assumption, used in guide comparisons only. |
| Vehicle Excise Duty | £200 – £640 per year | Sourced. Electric cars have paid VED since 1 April 2025. The £200 standard rate applies from year two; cars above the list-price threshold add the £440 Expensive Car Supplement in years two to six. See the Vehicle Excise Duty section below. |
| Petrol road funding | Included in fuel excise | Sourced. Fuel excise is levied on petrol and diesel at the point of sale, so petrol running costs on this site already include a road funding component that EV costs do not. |
What running cost figures exclude
The running cost figures on this site cover energy and servicing only. They do not include purchase price, depreciation, financing, insurance, registration, tyres, or battery replacement. Depreciation and insurance are usually larger than fuel for a new vehicle, so a running cost comparison is not a total cost of ownership comparison and should not be read as one.
Range and range loss
Estimated range is battery capacity divided by efficiency. Driving conditions are applied as an adjustment to efficiency, not to the battery.
| Condition | Efficiency adjustment | Basis |
|---|---|---|
| City driving | −25% | Assumption. Lower speeds and regenerative braking. |
| Mixed driving | −12% | Assumption |
| Typical driving | Baseline | The vehicle's rated efficiency |
| Highway driving | +15% | Assumption. Based on typical UK speed limits of 60 to 70 mph. |
| Fast highway | +25% | Assumption |
| Worst case | +50% | Assumption. Cold weather, highway speeds and cabin heating combined. |
These percentages are approximate and are not derived from a published dataset. Real variation depends on the vehicle, terrain, temperature, driving style and climate control use.
What the calculators do not account for
- Charging losses. Energy drawn from the wall is greater than energy stored in the battery, typically by a few per cent for DC and rather more for slow AC charging. The calculators treat energy added and energy paid for as the same quantity, so real costs are slightly higher than shown.
- Session and connection fees. Some public charging networks apply a per-session fee or an idle fee. Only the per-kWh price is modelled.
- Demand charges and supply charges. Home electricity bills include a daily supply charge that does not change with EV charging, and is therefore excluded.
- Solar. Charging from your own rooftop solar has a different cost basis again. Enter your own figure if this applies to you.
- Battery degradation. Usable capacity falls over a vehicle's life. All figures assume the battery's rated capacity.
- The charging curve. See the charging time note above.
Vehicle Excise Duty
Electric cars became liable for Vehicle Excise Duty on 1 April 2025, ending the exemption they had held since the current system began. These are the figures behind the EV road tax calculator and the ownership costs elsewhere on the site.
| Input | Value used | Basis |
|---|---|---|
| First-year rate, electric | £10 | Sourced. A nominal first-year rate for zero-emission cars. Petrol and diesel first-year rates are banded on CO₂ and can run to several thousand pounds. |
| Standard rate, from year two | £200 per year | Sourced, 2026/27. Applies to electric, petrol and diesel cars alike. |
| Expensive Car Supplement | £440 per year | Sourced, 2026/27. Charged in years two to six, so five years in total. |
| Supplement threshold, electric | £50,000 list price | Sourced. Raised from £40,000 on 1 April 2026 for fully electric cars only. |
| Supplement threshold, other fuels | £40,000 list price | Sourced. Unchanged for petrol, diesel and hybrids. |
Rates are uprated annually and thresholds have moved recently, so confirm with the DVLA before relying on these near a purchase. List price means the manufacturer’s price including factory options, not what you negotiated — a car specified just over a threshold pays the supplement even if the invoice came in under it.
The threshold split is the part most often got wrong. Since 1 April 2026 an electric car escapes the Expensive Car Supplement up to £50,000 while a petrol or diesel one crosses it at £40,000. A comparison that applies one figure to both will overstate the tax on the electric car by £2,200 across the five supplement years.
Review schedule
Prices move. This page and the constants behind it are reviewed together, and the review date shown at the top of this page is the date of the last review of the figures themselves — not the date the page was last edited.
If a figure here looks wrong, or you have a source that would let an assumption become a sourced value, please get in touch. Corrections are welcome and will be credited on this page.