musk introduced the powerwall device at a press conference in california last night and said the technology could change the world ' .
the device , which could be in homes by the end of summer , will be able to store electricity at night when it is cheaper that tesla founder elon musk has unveiled a ` revolutionary ' $ 3,000 -lrb- £ 1,980 -rrb- home battery which he claims can run an entire home for eight hours .
the left images shows the 10kwh version while on the right is 7kwh device that