Asda, the supermarket group owned by Wal-Mart, is to explore selling electricity to its UK business customers through its power services company Power4All.  Rivals Tesco and Sainsbury both considered entering the UK retail energy market as the sector underwent deregulation in the late 1990s, but scrapped the idea amid concerns over risks to their core brands.  Power4All would build on its expertise developed by Wal-Mart in the US, where it set up its own energy services group in late 2004 to supply energy to its stores in Texas.  The terms of Power4All’s licence from the UK’s Gas and Electricity Markets Authority restrict it to reselling power to business and commercial customers. Andy Bond, chief executive, told the Financial Times on Sunday that in the “medium term” the retailer hoped to extend to Asda’s customers a programme initially set up last year to provide its stores with “low-cost energy and energy from totally sustainable sources”.