Enter your own tariff, your own mileage and the petrol car you are replacing. Every assumption is on the screen and editable, so you can see which number the answer turns on. Nothing is sent anywhere; the calculation happens in your browser.
What this does and does not count
Counted: purchase price after any incentive you enter, electricity split between home and public charging at the efficiency figure on the model page, petrol at the consumption you enter, and depreciation using the estimated five-year residual.
Not counted: insurance, tyres, servicing, road tax and finance interest. They differ enough between drivers and countries that including a national average would make the answer look more precise than it is. Servicing does tend to favour the electric car.
Carbon is tailpipe plus generation only. It excludes manufacturing, where the electric car starts behind and catches up over the first few years of driving.
Every default value and its source is listed on the methodology page.
For the same arithmetic at the default assumptions, car by car, see what it costs to charge an electric car per month. For the whole ownership picture rather than the energy bill alone — purchase price, depreciation and the year the two cross over — see what an electric car really costs to run against petrol. If you do not know your own rate, charging cost by US state gives the published residential average for all fifty.
The three numbers that decide the answer
How much of your charging happens at home
This is the single biggest lever in the whole calculation, and it is bigger than the choice of car. Home electricity typically costs a third of what a public rapid charger costs. A driver who charges at home overnight and a driver who lives in a flat and relies on public rapid charging are having completely different financial experiences of the same vehicle. If you cannot charge at home, drag the slider down and watch what happens; for some drivers, the honest answer is that an electric car does not save money at all yet.
How far you actually drive
The saving is per kilometre, so the break-even point moves in direct proportion to mileage. A high-mileage driver can recover a substantial purchase premium in three or four years. A driver doing five thousand kilometres a year may never recover it at all, and should be making the decision on other grounds.
What the petrol car it replaces actually consumes
Comparing an electric SUV against an unusually economical small hatchback is where most optimistic savings claims come from. Use the real consumption of the car you would otherwise be driving, not a manufacturer figure and not a smaller class of car.
Common mistakes
- Using the manufacturer’s efficiency figure as if it were your own. Cold weather, motorway speeds and a roof box all move real consumption well above the official number. In winter, expect twenty to thirty percent worse.
- Assuming public charging costs the same as home charging. It rarely costs less than double, and at some networks it costs more per kilometre than petrol.
- Counting an incentive you are not eligible for. Most schemes have income, price or leasing conditions attached. Enter zero unless you have checked.
- Ignoring depreciation. On a three-year ownership it usually dwarfs the fuel saving in either direction. The residual figures here are estimates and are labelled as such.
- Treating carbon payback as instant. Building a battery has an emissions cost. An electric car starts behind its petrol equivalent and catches up over the first years of driving, sooner on a clean grid and later on a coal-heavy one.
Every default value in this calculator, and the source it came from, is listed on the methodology page. None of this is financial advice.