Payback is the point where what you have spent on a home charger equals what you would have spent keeping on with public charging instead. Before that point, the charger has cost you more. After it, every charge you put through it is saving money against the public alternative.
The figure that comes out the other end is a number of months. A charger that takes longer to pay back still usually wins on convenience: no walking to a car park, no card machine to find, no waiting for a bay. Payback tells you about the money. The rest of the decision is yours.
The two costs it sets against each other
Payback needs an annual cost for charging at home and an annual cost for charging in public, built on the same mileage. Mileage is the constant. Drive the same distance each year, and every mile you charge at home instead of in public shifts the comparison.
What decides the home-charging side
Home cost comes down to three things: how many miles you drive, how efficient the car is, and the rate you pay for electricity. Where you are on an electric-vehicle tariff with a cheaper overnight window, the charger needs to be scheduled to use it. That scheduling can sit with the charger or with the car, and getting it wrong lets some charging slip onto the standard rate without you noticing. The question of which device holds the schedule is covered on charger, tariff and car scheduling.
The VAT rate applied to domestic electricity also sits inside this number. It has moved before and can move again. See domestic electricity VAT falling to zero for the current position and the date it was read.
What decides the public-charging side
Public cost depends on how much of your charging you actually do away from home, and at what sort of charger. Prices at a slow public charger and a rapid one are not close. A driver who tops up mostly on rapids on motorways will see a payback nothing like a driver who uses a slow charger near work every day.
Current prices by charger type, with the month each was read, are set out on charging away from home. Check them before putting a figure into any calculation.
Paying by the kilowatt-hour makes the comparison possible to check in the first place. Under the Public Charge Point Regulations 2023 (SI 2023/1168), operators across the UK must show a price in pence per kilowatt-hour.
Where the installed price comes from
The other half of payback is what the charger cost to put in. A quote that only lists the charger and leaves out the cable run, the consumer-unit work, the earthing arrangement and the network-operator notification understates the number you need. See what a complete quote contains on the installation quote worked example before putting a single-line price into a payback sum.
Chargers themselves differ in price by whether they are tethered or socketed, whether they work offline, and what power they are rated at. Current list prices by specification are set out on the charger comparison table.
A grant reduces the installed price for the households that still qualify. The amount, who is eligible and the date the scheme ends belong together, and they are set out on charger grants.
What skews the payback figure
- Using a public price from one charger type for all public charging. Rapid and slow public prices differ enough that blending them into one average habit gives a payback that matches neither.
- Leaving the installed price as the unit's list price. Installation work is usually the larger part of what a charger actually costs to put in.
- Ignoring which device holds the schedule. A tariff's off-peak rate only applies to charging that happens in the off-peak window; if the car's own charge limit or timer overrides the charger's schedule, some charging slips onto the standard rate without the driver noticing.
- Forgetting the VAT position on each side. Domestic electricity and public charging have not always carried the same VAT treatment, and a change to either side moves the payback even where nothing about your driving has changed.
Working it out on your own figures
A payback figure built on national averages tells you about an average driver. Enter your figures into the home charger payback against public charging tool to put your own mileage, efficiency, tariff and installed price through the same arithmetic. Every default value it starts from is shown with its source and the date it was read, and you can overwrite any of them that do not match your situation.
The tool can only return as good an answer as the figures it is given, so it can give you a misleading payback if your own bill, tariff or quote has moved since the defaults were last read. Check the installed price against your own quote and the rate against your own tariff before relying on the result.