Power consumption in a non-volatile storage device is reduced by providing
reduced read pass voltages on unselected word lines during a read
operation. A programming status of one or more unselected word lines
which are after a selected word line on which storage elements are being
read is checked to determine whether the unselected word lines contain
programmed storage elements. When an unprogrammed word line is
identified, reduced read pass voltages are provided on that word line and
other word lines which are after that word line in a programming order.
The programming status can be determined by a flag stored in the word
line, for instance, or by reading the word line at the lowest read state.
The unselected word lines which are checked can be predetermined in a set
of word lines, or determined adaptively based on a position of the
selected word line.