The real cost of a public charging stop

Two drivers can pay the same price for electricity and get rather different costs per mile. One is driving an efficient car in mild weather; the other is covering a cold motorway journey with a heavily loaded vehicle. The tariff is identical, but the energy needed for the trip is not.

To compare public charging sensibly, connect the price at the charger to your own consumption. Then add any subscription and parking costs that come with the stop.

From electricity to distance

In miles per kWh, divide the electricity price by efficiency. At a sample rate of £0.60/kWh and 3 miles/kWh, the energy cost is 20p per mile. At 4 miles/kWh, it falls to 15p.

For kWh per 100 km, multiply instead. At a sample €0.50/kWh and 18 kWh/100 km, the energy costs €9 per 100 km. A US example at $0.40/kWh and 3 miles/kWh works out at about 13.3 cents per mile.

Use a consumption figure that matches the journeys you expect to make. If it excludes charging losses, the estimate will be lower than the cost of buying that energy at the meter. Receipts over several weeks give a useful check, especially if the battery starts and ends the period at a similar level.

The subscription break-even point

A monthly fee can pay for itself if you use enough discounted charging. For example, a plan costing $8 a month and cutting the rate by $0.10/kWh breaks even at 80 kWh. Below that volume, the fee costs more than the discount saves.

Use the actual provider’s rates and eligible sites for the decision. A subscription to a cheap network is of little use if its locations do not suit your regular journeys. Check whether the price applies through the operator’s own app, a roaming account or contactless payment; the same charger can offer different tariffs through each.

The bill beyond the energy

Parking charges, session fees, minimum charges and idle fees can change the total. They vary by network and jurisdiction, so look at the terms for the particular stop rather than carrying an assumption from one country to another.

In the UK, government guidance requires the maximum charging price to be displayed in p/kWh before charging and distinguishes separate third-party parking charges. Elsewhere, check the displayed billing basis and applicable local rules. Keep the receipt if the final amount differs from what was offered.

The most useful comparison is your own mix of charging. A household using public chargers every day faces a different bill from one buying a few motorway top-ups each month.

Sources

• UK government: Public Charge Point Regulations guidance
• Energy Saving Trust: charging electric vehicles