This article describes evolution of the hybrid cars involving an electrical outlet. The modifications made to the Prius at the Maker Faire take the hybrid concept to the next level. With an added battery back, new electronics, and a socket, the car becomes what is known as a plug-in hybrid electric vehicle. The conversions performed by CalCars have involved installing either lead-acid or nickel-metal hydride battery packs in the rear compartments of stock Priuses. The engineering for these conversions has followed an open-source model, with the design being discussed and improved through collaboration with volunteers on an Internet message board. EDrive Systems, an automotive company based in southern California, and Hymotion, a Toronto-based automotive supply company, have unveiled full conversion kits, including auxiliary battery packs, electronics, and control systems. According to experts, with a Hymotion plug-in pack, a Prius can run as much as 30 miles on electricity alone.