By Guy Taylor Tesla has hired a new head of operations to help lead the launch of its household energy supplier as Elon Musk presses ahead with his vision for houses to have a “virtual power plant” of batteries. Roxanne Inskip-Kaye, a former director of operations at the domestic provider Social Energy, joined the tech giant in June, according to LinkedIn. Social Energy was the first British energy operator to sign an agreement with National Grid to even out supply by exporting electricity and buying it back when prices lower. Last summer Tesla unveiled plans to sell electricity to British hou…