From 1 July 2013, all electric vehicles which emit 75g/km of CO2 or less and meet the Euro 5 standard for air quality, will qualify for a 100% discount from the London Congestion Charge if they are registered with TfL.
Plug-in hybrid electric cars and vans that are on the TfL approved list are currently eligible for the Electric Vehicle Discount and would qualify for the new Ultra Low Emission Discount.
Transport for London (TfL) is reducing the current 100% congestion charge discount for low-emission cars in the capital from 100g/km to 75g/km. This benefits ultra-low emitting vehicles (ULEVs) such as the Audi A3 e-tron and means few traditionally-powered vehicles will qualify for free entry into the Central London Congestion Charging Zone.
Article source: www.audi.co.uk