As of April 2019, electric vehicles are eligible for an exemption form the London Congestion Charge and they also don't pay the Ultra Low Emission Zone (ULEZ) charge.
In order to qualify for the congestion charge exemption, drivers will need to register their electric vehicle with Transport for London (TfL) at a cost of £10, which needs to be renewed each year.
The Congestion Charge zone runs 7:00-18:00 Monday-Friday and 12:00-18:00 Sat-Sun and bank holidays. There's no charge between Christmas Day and New Year's Day bank holiday (inclusive). Unregistered vehicles will need to pay £15 each day they are driven within the boundary, even if they're electric.
The Ultra Low Emission Zone, by contrast, runs 24 hours a day, seven days a week (except Christmas Day), within the same area of central London as the Congestion Charge. Most vehicles that aren't registered will have to pay £12.50 per day. Although heavier vehicles, such as lorries, may need to pay up to £100 per day.
That means a typical daily charge for a non-ULEZ compliant car to drive in London is £27.50 per day. Register an electric vehicle today to avoid paying more than you have to.