An electric car that doesn't emit C02 from its tailpipe can't be truly considered "emissions free" if the electricity used to power it was created by burning coal or natural gas, instead of from renewable sources, such as solar or wind power. Similarly, evaluating a vehicle's GHG impact by its driving, or use phase, alone doesn't tell the whole story. While alternative materials reduce mass somewhat, they do not always make up for the increased GHG emissions over the lifetime of the vehicle. The newest steel grades lower vehicle weight without increasing GHGs. For instance, when optimised with Advanced High-Strength Steel (AHSS), a 5-passenger car produces 2.6% LESS GHGs than aluminium applications in the same model over its total life cycle.