he electric company sent out a graph to compare electricity usage in kilowatt-hours for the years 1998 and999. The graph shows the usage of a particular household for two years.

In the month of October 1998 the consumption was 25 KW hour.
In the month of October 1999 the consumption was 50 KW hour.
Thus the difference is calculated as,
50 KW hour - 25 KW hour
= 25 KW hours
Thus the greatest difference was recorded in the month of October.