Oncor High Commercial Electric Bill Richardson Texas

Since Jan 2013, our electric bill that used to be around $250-$350 is now  around $500 mark, this is during low times. I am thinking it will jumo to $1000 in high season like summer time. When I call Oncor they say its the demand. I told them nothing has changed in our working habbits, we are using the electric same way for last 7-8 yeatrs now, why all of a sudden our demand increased. They do not have any proper answer. Only thing they sugest to read their demand related information on their website. What is demand and how they calculate it. It does not resolve my issue of high bills. Why all of a sudden my will is doubled.