Most Power Companies charge a bond if you are a new customer. This bond varies in amount, but by way of example Genesis Energy has a bond of $150 for electricity and $200 for electricity and gas.
The idea of a bond is that if you leave without fully paying your power bill the bond will cover most of it. Although in reality people who do not pay their power bill frequently don't pay their bond either.
This expence of a bond is something to consider when moving power companies. (And when moving house). For example Mercury requires all moving customers to undergo a credit check and if this is unsatisfactory, they charge a bond.
Also it is worth investigating when a bond can be waived. For example Gensis Energy will waive the bond if you say you are the home owner. (Incidently they will never actually check if you are the home owner, they just take your word for it.) They will also remove the bond if you set up a direct debit to pay the account.
So do not accept the bond being added, ask your electricity company when it will be removed, and in what circumstances they can waive it. Hopefully they will provide you with an answer that means you do not have to pay the bond.